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The resort to force must have a legal basis in order not to violate these prohibitions. The
legality of the use of force must be assessed in light of the particular facts and circumstances at
issue.209
1.11.3.1 Aggression. Aggression is the most serious and dangerous form of the
illegal use of force.210 Not every act of illegal use of force prohibited by Article 2(4) of the
Charter constitutes aggression.211 Initiating a war of aggression is a serious international
crime.212
U.N. General Assembly Resolution 3314 suggested considerations that the Security
Council should bear in mind in determining whether an act of aggression had occurred.213
Although this resolution states basic principles as guidance for such determinations, it recognizes
that whether an act of aggression has been committed must be considered in light of all the
circumstances of each particular case.214
209 See, e.g., William H. Taft IV, Legal Adviser, Department of State, & Todd F. Buchwald, Assistant Legal Adviser
for Political-Military Affairs, Department of State, Preemption, Iraq, and International Law, 97 AJIL 557 (2003)
(“In the end, each use of force must find legitimacy in the facts and circumstances that the state believes have made
it necessary. Each should be judged not on abstract concepts, but on the particular events that gave rise to it.”);
Daniel Webster, Letter to Mr. Fox, Apr. 24, 1841, reprinted in DANIEL WEBSTER, THE DIPLOMATIC AND OFFICIAL
PAPERS OF DANIEL WEBSTER, WHILE SECRETARY OF STATE 105 (1848) (“It is admitted that a just right of self-
defense attaches always to nations as well as to individuals, and is equally necessary for the preservation of both.
But the extent of this right is a question to be judged of by the circumstances of each particular case;”).
210 Definition of Aggression, preamble ¶5, Annex to U.N. GENERAL ASSEMBLY RESOLUTION 3314 (XXIX),
Definition of Aggression, U.N. Doc. A/RES/3314 (XXIX) (Dec. 14, 1974) (“Considering also that, since aggression
is the most serious and dangerous form of the illegal use of force, being fraught, in the conditions created by the
existence of all types of weapons of mass destruction, with the possible threat of a world conflict and all its
catastrophic consequences, aggression should be defined at the present stage.”).
211 Joseph Sanders, Rapporteur, The Special Committee on the Question of Defining Aggression, Report of the
Special Committee on the Question of Defining Aggression, Annex 1: Views expressed by members of the Special
Committee at the concluding stage of the Special Committee’s session, U.N. General Assembly Official Records:
Twenty-Ninth Session Supplement No. 19, U.N. Doc. A/9619, 22-23 (Mar. 11-Apr. 12, 1974) (“Mr.
ROSENSTOCK (United States of America) … The fifth preambular paragraph, while recognizing the dangers
which would flow from an illegal use of force amounting to aggression, correctly stated the view that not every act
of force in violation of the Charter constituted aggression.”).
212 United States, et al. v. Göring, et al., Judgment, I TRIAL OF THE MAJOR WAR CRIMINALS BEFORE THE IMT 421
(“To initiate a war of aggression, therefore, is not only an international crime; it is the supreme international crime
differing only from other war crimes in that it contains within itself the accumulated evil of the whole.”).
213 Joseph Sanders, Rapporteur, The Special Committee on the Question of Defining Aggression, Report of the
Special Committee on the Question of Defining Aggression, Annex 1: Views expressed by members of the Special
Committee at the concluding stage of the Special Committee’s session, U.N. General Assembly Official Records:
Twenty-Ninth Session Supplement No. 19, U.N. Doc. A/9619, 22-23 (Mar. 11-Apr. 12, 1974) (“Mr.
ROSENSTOCK (United States of America) … The text that had been produced was a recommendation of the
General Assembly for use by the Security Council. … In article 2, the definition suggested the considerations which
the Security Council should bear in mind in determining whether an act of aggression had occurred.”).
214 Definition of Aggression, preamble ¶10, Annex to U.N. GENERAL ASSEMBLY RESOLUTION 3314 (XXIX),
Definition of Aggression, U.N. Doc. A/RES/3314 (XXIX) (Dec. 14, 1974) (“Believing that, although the question
whether an act of aggression has been committed must be considered in the light of all the circumstances of each
particular case, it is nevertheless desirable to formulate basic principles as guidance for such determination,”).
44
The United States has expressed the view that the definition of the act of aggression in
the Kampala amendments to the Rome Statute does not reflect customary international law.215
1.11.4 Rationales for the Resort to Force.
1.11.4.1 Use of Force in Self-Defense. The right to use force in self-defense is an
inherent right of States.216
1.11.4.2 Use of Force Authorized by the U.N. Security Council Acting Under
Chapter VII of the Charter of the United Nations. Chapter VII of the Charter of the United
Nations provides that the U.N. Security Council may take such action by air, sea, or land forces
as may be necessary to maintain or restore international peace or security, including
demonstrations, blockade, and other military operations.217
1.11.4.3 Use of Force With the Consent of the Territorial State. Military action in
the territory of another State is not a violation of Article 2(4)’s prohibition against the use of
force against that State where it consents to such military action.218
1.11.4.4 Humanitarian Intervention. Violations of law of war treaties applicable
to non-international armed conflict generally have not been understood to provide an
independent basis for intervening in a State.219
Although the United Kingdom and certain other States have argued that intervention for
humanitarian reasons may be a legal basis for the resort to force, the United States has not
215 Refer to § 18.20.3.4 (ICC and the Crime of Aggression).
216 Refer to § 1.11.5 (Use of Force in Self-Defense).
217 U.N. CHARTER art. 42 (“Should the Security Council consider that measures provided for in Article 41 would be
inadequate or have proved to be inadequate, it may take such action by air, sea, or land forces as may be necessary
to maintain or restore international peace and security. Such action may include demonstrations, blockade, and
other operations by air, sea, or land forces of Members of the United Nations.”).
218 For example, Davis R. Robinson, Department of State Legal Adviser, Letter to Professor Edward Gordon,
Chairman of the Committee on Grenada Section on International Law and Practice American Bar Association on
The Legal Position of the United States on the Action taken in Grenada (Feb. 10, 1984), reprinted in 18
INTERNATIONAL LAWYERS 381 (1984) (“In the case of the action taken in Grenada, the legal position of the United
States was based upon the application of a combination of three well established principles of international law…
(1) the lawful governmental authorities of a State may invite the assistance in its territory of military forces of other
states or collective organizations in dealing with internal disorder as well as external threats.”); Statement of the
U.S. Government, attached to Adlai E. Stevenson, Letter Dated 24 November 1964 From the Permanent
Representative of the United States of America Addressed to the President of the Security Council, U.N. Doc.
S/6062, Nov. 24, 1964 (“The United States Government has just received confirmation that a short time ago - early
morning of 24 November in the Congo - a unit of Belgian paratroopers, carried by United States military transport
planes, landed at Stanleyville in the Congo. This landing has been made (1) with the authorization of the
Government of the Congo, (2) in conformity with our adherence to the Geneva Conventions, and (3) in exercise of
our clear responsibility to protect United States citizens under the circumstances existing in the Stanleyville area.”).
219 Refer to § 17.18.1 (Duty of Non-Belligerent States to Refrain From Supporting Hostilities by Non-State Armed
Groups Against Other States).
45
adopted this legal rationale.220 Consistent with this view, the United States did not adopt this
theory as a legal rationale for NATO’s military action to address the humanitarian catastrophe in
Kosovo in 1999, but rather expressed the view that such action was justified on the basis of a
number of factors.221
Military action for humanitarian reasons may, however, be authorized by the U.N.
Security Council.222
1.11.5 Use of Force in Self-Defense. Article 51 of the Charter of the United Nations
provides that “[n]othing in the present Charter shall impair the inherent right of individual or
collective self-defence if an armed attack occurs against a Member of the United Nations, until
the Security Council has taken measures necessary to maintain international peace and
security.”223
220 William H. Taft IV, Legal Adviser, Department of State, Role and Significance of International Law Governing
the Use of Force in the New Global Context Confronting the United States After 9/11: remarks regarding the use of
force under international law (Oct. 27, 2004) (“Of particular note, the idea that humanitarian catastrophes must be
avoided has been asserted as a reason for rethinking what actions international law permits in a number of situations.
NATO’s intervention in Kosovo in 1999 is a case to consider in this connection. In defending the legality of
NATO’s actions, the United Kingdom and several other allies asserted a doctrine of humanitarian intervention,
under which states have a right to use force if it is necessary to prevent genocide, a major loss of civilian life, or a
large scale forced movement of a population, which would destabilize other states and threaten international peace
and security. In this view, the humanitarian intervention doctrine is often presented as a necessary extension of
humanitarian law as it has evolved since 1945. Significantly, the doctrine was invoked in the absence of
authorization by the UN Security Council. The United States did not, however, adopt this theory as a basis for the
NATO intervention in Kosovo, and instead pointed to a range of other factors to justify its participation in the
Kosovo campaign.”).
221 David Andrews, Legal Adviser, Department of State, Oral Proceedings, May 11, 1999, Legality of Use of Force
(Yugoslavia v. United States) I.C.J. 10 (¶1.7) (“As you have already heard, the actions of the Members of the NATO
Alliance find their justification in a number of factors. These include:
- The humanitarian catastrophe that has
engulfed the people of Kosovo as a brutal and unlawful campaign of ethnic cleansing has forced many hundreds of
thousands to flee their homes and has severely endangered their lives and well-being; - The acute threat of the
actions of the Federal Republic of Yugoslavia to the security of neighbouring States, including threat posed by
extremely heavy flows of refugees and armed incursions into their territories; - The serious violation of international
humanitarian law and human rights obligations by forces under the control of the Federal Republic of Yugoslavia,
including widespread murder, disappearances, rape, theft and destruction of property; and, finally - The resolutions
of the Security Council, which have determined that the actions of the Federal Republic of Yugoslavia constitute a
threat to peace and security in the region and, pursuant to Chapter VII of the Charter, demanded a halt to such
actions.”).
222 For example, U.N. SECURITY COUNCIL RESOLUTION 1973, U.N. Doc. S/RES/1973, ¶4 (Mar. 17, 2011) (“[This
Resolution] [a]uthorizes Member States that have notified the Secretary-General, acting nationally or through
regional organizations or arrangements, and acting in cooperation with the Secretary-General, to take all necessary
measures, notwithstanding paragraph 9 of resolution 1970 (2011), to protect civilians and civilian populated areas
under threat of attack in the Libyan Arab Jamahiriya, including Benghazi, while excluding a foreign occupation
force of any form on any part of Libyan territory … .”).
223 U.N. CHARTER art. 51.
46
The Charter of the United Nations was not intended to supersede a State’s inherent right
of individual or collective self-defense in customary international law.224
To constitute legitimate self-defense under customary international law, it is generally
understood that the defending State’s actions must be necessary.225 For example, reasonably
available peaceful alternatives must be exhausted.226 In addition, the measures taken in self-
defense must be proportionate to the nature of the threat being addressed.227
1.11.5.1 Responding to an Imminent Threat of an Attack. The text of Article 51
of the Charter of the United Nations refers to the right of self-defense “if an armed attack occurs
against a Member of the United Nations.”228 Under customary international law, States had, and
continue to have, the right to take measures in response to imminent attacks.229
1.11.5.2 Use of Force Versus Armed Attack. The United States has long taken the
position that the inherent right of self-defense potentially applies against any illegal use of
force.230 Others, however, would be inclined to draw more of a distinction between “armed
attacks” and uses of force that do not give rise to the right to use force in self-defense.231
224 Abraham D. Sofaer, Terrorism, the Law, and the National Defense, 126 MILITARY LAW REVIEW 89, 94 (1989)
(“The United States rejects the notion that the U.N. Charter supersedes customary international law on the right of
self-defense. Article 51 characterizes that right as ‘inherent’ in order to prevent its limitation based on any provision
in the Charter. We have always construed the phrase ‘armed attack’ in a reasonable manner, consistent with a
customary practice that enables any State effectively to protect itself and its citizens from every illegal use of force
aimed at the State.”).
225 William H. Taft IV, Legal Adviser, Department of State, Self-Defense and the Oil Platforms Decision, 29 YALE
JOURNAL OF INTERNATIONAL LAW 295, 304 (2004) (“To constitute legitimate self-defense under customary
international law, it is generally understood that the defending State’s actions must be both ‘necessary’ and
‘proportional.’”).
226 Refer to § 1.11.1.3 (All Peaceful Alternatives Must Have Been Exhausted (Necessity - Jus ad Bellum)).
227 Refer to § 1.11.1.2 (The Means Must Be Proportionate to the Just Cause (Proportionality - Jus ad Bellum)).
228 U.N. CHARTER art. 51.
229 Lord Peter Henry Goldsmith, Attorney General, United Kingdom, Oral Answers to Questions, Apr. 21, 2004,
HANSARD 660 HOUSE OF COMMONS DEBATES §§ 370-71 (“It is argued by some that the language of Article 51
provides for a right of self-defence only in response to an actual armed attack. However, it has been the consistent
position of successive United Kingdom Governments over many years that the right of self-defence under
international law includes the right to use force where an armed attack is imminent. It is clear that the language of
Article 51 was not intended to create a new right of self-defence. Article 51 recognises the inherent right of self-
defence that states enjoy under international law. … It is not a new invention. The charter did not therefore affect
the scope of the right of self-defence existing at that time in customary international law, which included the right to
use force in anticipation of an imminent armed attack.”).
230 See Abraham D. Sofaer, Terrorism, the Law, and the National Defense, 126 MILITARY LAW REVIEW 89, 92-93
(1989) (“The United States has long assumed that the inherent right of self defense potentially applies against any
illegal use of force, and that it extends to any group or State that can properly be regarded as responsible for such
activities. These assumptions are supported in customary practice.”). See also William H. Taft IV, Legal Adviser,
Department of State, Self-Defense and the Oil Platforms Decision, 29 YALE JOURNAL OF INTERNATIONAL LAW 295,
300-01 (2004) (“A requirement that an attack reach a certain level of gravity before triggering a right of self-defense
would make the use of force more rather than less likely, because it would encourage States to engage in a series of
small-scale military attacks, in the hope that they could do so without being subject to defensive responses.
Moreover, if States were required to wait until attacks reached a high level of gravity before responding with force,
47
1.11.5.3 Use of Force to Protect Nationals Abroad. A State’s right to use force in
self-defense may be understood to include the right to use force to protect its nationals abroad.232
The United States has taken action to protect U.S. nationals abroad when the government of the
territory in which they are located was unwilling or unable to protect them.233 A State need not
await actual violence against its nationals before taking such action if an attack against them is
imminent.234
1.11.5.4 Right of Self-Defense Against Non-State Actors. The inherent right of
self-defense, recognized in Article 51 of the Charter of the United Nations, applies in response to
any “armed attack,” not just attacks that originate with States.235 As with any other exercise of
their eventual response would likely be much greater, making it more difficult to prevent disputes from escalating
into full-scale military conflicts.”).
231 See, e.g., Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. United States), Merits,
Judgment, 1986 I.C.J. 14, 101 (¶191) (“As regards certain particular aspects of the principle in question, it will be
necessary to distinguish the most grave forms of the use of force (those constituting an armed attack) from other less
grave forms.”); id. at 126-27 (¶247) (“So far as regards the allegations of supply of arms by Nicaragua to the armed
opposition in El Salvador, the Court has indicated that while the concept of an armed attack includes the despatch by
one State of armed bands into the territory of another State, the supply of arms and other support to such bands
cannot be equated with armed attack. Nevertheless, such activities may well constitute a breach of the principle of
the non-use of force and an intervention in the internal affairs of a State, that is, a form of conduct which is certainly
wrongful, but is of lesser gravity than an armed attack.”).
232 Ambassador William Scranton, U.S. Representative to the United Nations, Statement in the U.N. Security
Council regarding Israeli action at Entebbe, Jul. 12, 1976, 1976 DIGEST OF UNITED STATES PRACTICE IN
INTERNATIONAL LAW 150 (“[T]here is a well-established right to use limited force for the protection of one’s own
nationals from an imminent threat of injury or death in a situation where the State in whose territory they are located
either is unwilling or unable to protect them. The right, flowing from the right of self defense, is limited to such use
of force as is necessary and appropriate to protect threatened nationals from injury.”).
233 For example, Jimmy Carter, Letter to Thomas P. O’Neal, Jr., Speaker of the House of Representatives, and
Warren G. Magnuson, President pro tempore of the Senate regarding the rescue attempt for American hostages in
Iran, Apr. 26, 1980, 1980-I PUBLIC PAPERS OF THE PRESIDENTS 779 (“In carrying out this operation [to rescue the
American hostages in the U.S. embassy in Tehran] the United States was acting wholly within its right, in
accordance with Article 51 of the United Nations Charter, to protect and rescue its citizens where the government of
the territory in which they are located is unwilling or unable to protect them.”).
234 Kenneth W. Dam, Deputy Secretary of State, Statement before the House Committee on Foreign Affairs, Nov. 2,
1983, reprinted in 78 AJIL 200, 203-04 (1984) (“U.S. actions have been based on three legal grounds: … Third,
U.S. action to secure and evacuate endangered U.S. citizens on the island was undertaken in accordance with well-
established principles of international law regarding the protection of one’s nationals. That the circumstances
warranted this action has been amply documented by the returning students themselves. There is absolutely no
requirement of international law that compelled the United States to await further deterioration of the situation that
would have jeopardized a successful operation. Nor was the United States required to await actual violence against
U.S. citizens before rescuing them from the anarchic and threatening conditions the students have described.”).
235 See, e.g., In re Guantanamo Bay Litigation, Respondents’ Memorandum Regarding the Government’s Detention
Authority Relative to Detainees Held at Guantanamo Bay, Misc. No. 08-442, 4 (D.D.C., Mar. 13, 2009) (“Under
international law, nations lawfully can use military force in an armed conflict against irregular terrorist groups such
as al-Qaida. The United Nations Charter, for example, recognizes the inherent right of states to use force in self
defense in response to any ‘armed attack,’ not just attacks that originate with states. United Nations Charter, art.
51.”); U.S. Additional Response to the Request for Precautionary Measures—Detention of Enemy Combatants at
Guantanamo Bay, Cuba, Inter-American Commission on Human Rights, Jul. 15, 2002, 2002 DIGEST OF UNITED
STATES PRACTICE IN INTERNATIONAL LAW 1008, 1011-12 (“The terrorist attacks of September 11 were not ordinary
criminal acts. … The international community has clearly recognized the right of the United States and allied forces
48
the right of self-defense, actions taken in self-defense against non-State actors must comply with
applicable international law.236
1.11.5.5 Right of Collective Self-Defense. Article 51 of the Charter of the United
Nations also recognizes a right of States to engage in collective self-defense with a State that can
legitimately invoke its own right of national self-defense. Collective self-defense of a State must
proceed with that State’s consent, although this consent need not necessarily be expressed in the
form of an explicit request.237
Some treaties include commitments by States to assist one another in collective self-
defense.238
1.11.5.6 Reporting to the U.N. Security Council. Measures taken in the exercise
of national self-defense shall be immediately reported to the U.N. Security Council.239
to resort to armed force in self-defense in response to these attacks. For instance, the United Nations explicitly
recognized the ‘inherent right of individual and collective self-defence’ immediately following September 11. It is
in this context that NATO and others recognized that the September 11 attacks constituted an ‘armed attack,’ a
conclusion inherent in the UN Security Council’s recognition of the right of self-defense.”).
236 Refer to § 17.18.2 (Duty of Belligerent States to Respect the Sovereignty of Other States).
237 See also BRUNO SIMMA, THE CHARTER OF THE UNITED NATIONS: A COMMENTARY 675 (1994) (“Art. 51 of the
Charter allows not only individual, but also collective self-defence. The latter is not, as the wording might suggest,
restricted to a common, co-ordinated exercise of the right to individual self-defence by a number of states. … It is
not required for the exercise of the right of collective self-defence that the state invoking the right be under an
obligation resulting from a treaty of assistance. Rather, it is sufficient, but also necessary, that the support be given
with the consent of the attacked state. But this consent does not, as the ICJ states for the right of self-defence under
customary law, need to be declared in the form of an explicit ‘request’.”).
238 For example, The North Atlantic Treaty, Washington, D.C., Apr. 4, 1949, art. 5 (“The Parties agree that an armed
attack against one or more of them in Europe or North America shall be considered an attack against them all and
consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or
collective self-defense recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties
so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary,
including the use of armed force, to restore and maintain the security of the North Atlantic area.”).
239 U.N. CHARTER art. 51 (“Measures taken by Members in the exercise of this right of self-defence shall be
immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the
Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain
or restore international peace and security.”).
49
II - Principles
Chapter Contents
2.1 Introduction
2.2 Military Necessity
2.3 Humanity
2.4 Proportionality
2.5 Distinction
2.6 Honor
2.1 INTRODUCTION
Three interdependent principles - military necessity, humanity, and honor - provide the
foundation for other law of war principles, such as proportionality and distinction, and most of
the treaty and customary rules of the law of war.
This Chapter briefly addresses certain specific rules to illustrate these foundational
principles. For more information about a specific rule, practitioners should refer to the cross-
referenced section that addresses that rule.1
2.1.1 Legal Principles as Part of International Law. General principles of law common to
the major legal systems of the world are a recognized part of international law.2 Law of war
principles have been understood to be included in this category of international law.3
1 Refer to § 1.2.3 (Use of Cross-References in This Manual).
2 See ICJ STATUTE art. 38(1)(c) (providing that “the general principles of law recognized by civilized nations” are a
source of applicable law for the court); I RESTATEMENT (THIRD) OF FOREIGN RELATIONS LAW OF THE UNITED
STATES 24 (§102(1)(c)(4)) (1987) (including “general principles common to the major legal systems of the world,”
among sources of international law); Thirty Hogsheads of Sugar v. Boyle, 13 U.S. 191, 198 (1815) (Marshall, C.J.)
(ascertaining international law includes “resort to the great principles of reason and justice”).
3 See BOTHE, PARTSCH, & SOLF, NEW RULES 44 (AP I art. 1, ¶2.10) (“Following the original clause in the preamble
of the 1899 IV. Hague Convention on Land Warfare (para. 9) and para. 4 of the denunciation clause in the
Conventions (63/62/142/158) these principles are stated in the present text to be part of international law. They are
‘general principles of law’ in the sense of Art. 38 of the Statute of the ICJ.”); Speech by Baron Descamps on the
Rules of Law to be applied, Annex No. 1 to 14th Meeting (Private), held at the Peace Palace, the Hague, on July
2nd, 1920, PERMANENT COURT OF INTERNATIONAL JUSTICE, ADVISORY COMMITTEE OF JURISTS, PROCÈS-VERBAUX
OF THE PROCEEDINGS OF THE COMMITTEE: JUNE 16TH - JULY 24TH 1920 WITH ANNEXES 322, 323-24 (1920) (“The
only question is, -- how to make unerring rules for the judge’s guidance. … I allow him to take into consideration
the legal conscience of civilised nations, which is illustrated so strikingly on certain occasions. … [L]isten to this
solemn declaration of the Powers, placed at the beginning of the Convention dealing with laws and customs of war
on land: ‘Until a more complete code of the laws of war has been issued, the high contracting Parties deem it
expedient to declare that, in cases not included in the Regulations adopted by them, populations and belligerents
remain under the protection and the rule of the principles of the law of nations, as they result from the usages
established among civilised peoples, from the laws of humanity, and the dictates of the public conscience.’ … I am
convinced that the assembly of all the States does not and cannot intend, in dealing with the state of peace, to abjure
principles which are clearly intended to be applied in war.”).
50
2.1.2 Uses of Law of War Principles. Law of war principles provide the foundation for
the specific law of war rules. Legal principles, however, are not as specific as rules, and thus
interpretations of how principles apply to a given situation may vary.
Law of war principles: (1) help practitioners interpret and apply specific treaty or
customary rules; (2) provide a general guide for conduct during war when no specific rule
applies; and (3) work as interdependent and reinforcing parts of a coherent system.
2.1.2.1 Law of War Principles as an Aid in Interpreting and Applying Law of War
Rules. Understanding law of war principles helps practitioners interpret and apply specific law
of war rules. For example, the principle of military necessity has been incorporated into specific
law of war rules.4 Similarly, the principle of humanity can assist in the proper interpretation and
application of law of war rules that are based on humanitarian considerations.5
2.1.2.2 Law of War Principles as a General Guide. When no specific rule
applies, the principles of the law of war form the general guide for conduct during war.
States have reflected this idea in certain treaty provisions, including the “Martens
Clause,” which make clear that situations not covered by the treaty remain governed by
principles of international law.6
The considerable progress States have made in developing specific law of war rules,
however, has lessened the need to rely solely on these principles to guide conduct during war.7
2.1.2.3 Law of War Principles as a Coherent System. Law of war principles work
as interdependent and reinforcing parts of a coherent system.
Military necessity justifies certain actions necessary to defeat the enemy as quickly and
efficiently as possible.8 Conversely, humanity forbids actions unnecessary to achieve that
object.9 Proportionality requires that even when actions may be justified by military necessity,
such actions not be unreasonable or excessive.10 Distinction underpins the parties’ responsibility
to comport their behavior with military necessity, humanity, and proportionality by requiring
parties to a conflict to apply certain legal categories, principally the distinction between the
4 Refer to § 2.2.2.2 (Incorporation of Military Necessity Into Law of War Rules).
5 Refer to § 2.3.2 (Humanity and Law of War Rules).
6 Refer to § 19.8.3 (Martens Clause).
7 TUCKER, THE LAW OF WAR AND NEUTRALITY AT SEA 46-47 (“Where the general principles of the law of war have
received—through the agreement of states—detailed application in the form of specific rules, the question of the
proper interpretation of these general principles can only be answered by an examination of the former. Hence, to
the extent that the conduct of war is increasingly subjected to such regulation resort to the general principles of the
law of war must become, in turn, correspondingly less frequent. The reason for this is simply that the essential
function of these general principles is to provide a guide for determining the legal status of weapons and methods of
warfare where no more specific rule is applicable.”).
8 Refer to § 2.2 (Military Necessity).
9 Refer to § 2.3 (Humanity).
10 Refer to § 2.4 (Proportionality).
51
armed forces and the civilian population.11 Lastly, honor supports the entire system and gives
parties confidence in it.12
2.2 MILITARY NECESSITY
Military necessity may be defined as the principle that justifies the use of all measures
needed to defeat the enemy as quickly and efficiently as possible that are not prohibited by the
law of war. Military necessity has been defined in military publications,13 judicial decisions,14
and scholarly works.15
2.2.1 Military Necessity as a Justification. Military necessity justifies actions, such as
destroying and seizing persons and property.16 Thus, military necessity underlies law of war
11 Refer to § 2.5 (Distinction).
12 Refer to § 2.6 (Honor).
13 See LIEBER CODE art. 14 (“Military necessity, as understood by modern civilized nations, consists in the necessity
of those measures which are indispensable for securing the ends of the war, and which are lawful according to the
modern law and usages of war.”); 1914 RULES OF LAND WARFARE ¶¶9-11 (“a belligerent is justified in applying any
amount and any kind of force which is necessary for the purpose of the war; that is, the complete submission of the
enemy at the earliest possible moment with the least expenditure of men and money. … Military necessity justifies a
resort to all measures which are indispensable for securing this object and which are not forbidden by the modern
laws and customs of war.”); 1940 RULES OF LAND WARFARE ¶4a (“a belligerent is justified in applying any amount
and any kind of force to compel the complete submission of the enemy with the least possible expenditure of time,
life, and money.”); 1956 FM 27-10 (Change No. 1 1976) ¶3 (“that principle which justifies those measures not
forbidden by international law which are indispensable for securing the complete submission of the enemy as soon
as possible.”); 1958 UK MANUAL ¶3 ( “a belligerent is justified in applying compulsion and force of any kind, to the
extent necessary for the realization of the purpose of war, that is, the complete submission of the enemy at the
earliest possible moment with the least possible expenditure of men, resources, and money.”); 2004 UK MANUAL
¶2.2 (“Military necessity is now defined as ‘the principle whereby a belligerent has the right to apply any measures
which are required to bring about the successful conclusion of a military operation and which are not forbidden by
the laws of war.’ Put another way, a state engaged in an armed conflict may use that degree and kind of force, not
otherwise prohibited by the law of armed conflict, that is required in order to achieve the legitimate purpose of the
conflict, namely the complete or partial submission of the enemy at the earliest possible moment with the minimum
expenditure of life and resources.”); NATO, Glossary of Terms and Definitions, AAP-6 at 2-M-6 (2009) (defining
military necessity as “the principle whereby a belligerent has the right to apply any measures which are required to
bring about the successful conclusion of a military operation and which are not forbidden by the laws of war.”).
14 See United States v. List, et al. (The Hostage Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1253
(“Military necessity permits a belligerent, subject to the laws of war, to apply any amount and kind of force to
compel the complete submission of the enemy with the least possible expenditure of time, life, and money.”).
15 See GREENSPAN, MODERN LAW OF LAND WARFARE 313-14 (military necessity is “the right to apply that amount
and kind of force which is necessary to compel the submission of the enemy with the least possible expenditure of
time, life, and money); CHARLES HENRY HYDE, II INTERNATIONAL LAW: CHIEFLY AS INTERPRETED AND APPLIED
BY THE UNITED STATES 299-300 (1922) (“Military necessity, as understood by the United States, justifies a resort to
all measures which are indispensable to bring about the complete submission of the enemy by means of regulated
violence and which are not forbidden by the modern laws and customs of war.”); WILLIAM EDWARD HALL, A
TREATISE ON INTERNATIONAL LAW 63 (§17) (A. Pearce Higgins, ed., 7th ed., 1917) (“When violence is permitted at
all, the amount which is permissible is that which is necessary to attain the object proposed. The measure of the
violence which is permitted in war is therefore that which is required to reduce the enemy to terms.”).
16 See LIEBER CODE art. 15 (“Military necessity admits of all destruction of life or limb of armed enemies, … it
allows of the capturing of every armed enemy, and every enemy of importance to the hostile government, or of
peculiar danger to the captor; it allows of all destruction of property, and obstruction of the ways and channels of
52
concepts that explain when persons and property may be the object of attack, e.g., the concepts
of “taking a direct part in hostilities”17 and “military objective.”18
Military necessity may justify not only violence and destruction, but also alternative
means of subduing the enemy.19 For example, military necessity may justify the capture of
enemy persons,20 or non-forcible measures, such as propaganda and intelligence-gathering.21
Military necessity also justifies certain incidental harms that inevitably result from the
actions it justifies.22 The extent to which military necessity justifies such harms is addressed by
the principle of proportionality.23
2.2.2 Military Necessity and Law of War Rules.
2.2.2.1 Military Necessity Does Not Justify Actions Prohibited by the Law of War.
Military necessity does not justify actions that are prohibited by the law of war.
From the late 19th Century through World War II, Germany asserted that military
necessity could override specific law of war rules (Kriegsraeson geht vor Kriegsmanier -
“necessity in war overrules the manner of warfare”).24 This view was strongly criticized.25 Post-
World War II war crimes tribunals rejected it as well.26
traffic, travel, or communication, and of all withholding of sustenance or means of life from the enemy; of the
appropriation of whatever an enemy’s country affords necessary for the subsistence and safety of the army, and of
such deception as does not involve the breaking of good faith either positively pledged, regarding agreements
entered into during the war, or supposed by the modern law of war to exist.”); United States v. List, et al. (The
Hostage Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1253-54 (“In general, [military necessity]
sanctions measures by an occupant necessary to protect the safety of his forces and to facilitate the success of his
operations. It permits the destruction of life of armed enemies and other persons whose destruction is incidentally
unavoidable by the armed conflicts of the war; it allows the capturing of armed enemies and others of peculiar
danger … . It is lawful to destroy railways, lines of communication, or any other property that might be utilized by
the enemy. Private homes and churches even may be destroyed if necessary for military operations.”).
17 Refer to § 5.9 (Civilians Taking a Direct Part in Hostilities).
18 Refer to § 5.7 (Military Objective).
19 For example, Abraham Lincoln, The Emancipation Proclamation, Jan. 1, 1863, reprinted in 12 STAT. 1268
(justifying emancipation of slaves held in rebellious states as “warranted by the Constitution, upon military
necessity”).
20 Refer to § 8.1.3.1 (Detention Authority).
21 Refer to § 5.26 (Non-Forcible Means and Methods of Warfare).
22 See LIEBER CODE art. 15 (“Military necessity admits of all destruction of life or limb of … persons whose
destruction is incidentally unavoidable in the armed contests of the war;”); United States v. List, et al. (The Hostage
Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1253-54 (military necessity “permits the destruction of life
of … persons whose destruction is incidentally unavoidable by the armed conflicts of the war;”).
23 Refer to § 2.4 (Proportionality).
24 See LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW 231-32 (§69) (“In accordance with the German
proverb, Kriegsraeson geht vor Kriegsmanier (necessity in war overrules the manner of warfare), many German
authors before the First World War were maintaining that the laws of war lose their binding force in case of extreme
necessity.”); United States, et al. v. Göring, et al., Judgment, I TRIAL OF THE MAJOR WAR CRIMINALS BEFORE THE
53
Military necessity cannot justify departures from the law of war because States have
crafted the law of war specifically with war’s exigencies in mind.27 In devising law of war rules,
States considered military requirements.28 Thus, prohibitions on conduct in the law of war may
be understood to reflect States’ determinations that such conduct is militarily unnecessary per se.
IMT 227 (“The truth remains that War Crimes were committed on a vast scale, never before seen in the history of
war. … There can be no doubt that the majority of them arose from the Nazi conception of ‘total war’, with which
the aggressive wars were waged. For in this conception of ‘total war’, the moral ideas underlying the conventions
which seek to make war more humane are no longer regarded as having force or validity. Everything is made
subordinate to the overmastering dictates of war. Rules, regulations, assurances, and treaties all alike are of no
moment; and so, freed from the restraining influence of international law, the aggressive war is conducted by the
Nazi leaders in the most barbaric way. Accordingly, War Crimes were committed when and wherever the Führer
and his close associates thought them to be advantageous.”).
25 See, e.g., Elihu Root, Opening Address, 15 PROCEEDINGS OF THE AMERICAN SOCIETY OF INTERNATIONAL LAW 1,
2 (1921) (“More important still is a fact which threatens the foundation of all international law. The doctrine of
kriegsraison has not been destroyed. It was asserted by Bethman Hollweg at the beginning of the war when he
sought to justify the plain and acknowledged violation of international law in the invasion of Belgium upon the
ground of military necessity. The doctrine practically is that if a belligerent deems it necessary for the success of its
military operations to violate a rule of international law, the violation is permissible. As the belligerent is to be the
sole judge of the necessity, the doctrine really is that a belligerent may violate the law or repudiate it or ignore it
whenever that is deemed to be for its military advantage. The alleged necessity in the case of the German invasion
of Belgium was simply that Belgium was deemed to be the most advantageous avenue through which to attack
France. Of course, if that doctrine is to be maintained, there is no more international law, for the doctrine cannot be
confined to the laws specifically relating to war on land and sea. With a nation at liberty to declare war, there are
few rules of peaceful intercourse, the violation of which may not be alleged to have some possible bearing upon a
military advantage, and a law which may rightfully be set aside by those whom it is intended to restrain is no law at
all.”).
26 See, e.g., United States v. List, et al. (The Hostage Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1255-
56 (“It is apparent from the evidence of these defendants that they considered military necessity, a matter to be
determined by them, a complete justification of their acts. We do not concur in the view that the rules of warfare are
anything less than they purport to be. Military necessity or expediency do not justify a violation of positive rules.”);
United States v. Krupp, et al., IX TRIALS OF WAR CRIMINALS BEFORE THE NMT 1340 (rejecting defense counsel
argument that Hague IV and Hague IV Reg. rules did not apply in cases of “total war”). See also Trial of Gunther
Thiele and Georg Steinert, III U.N. LAW REPORTS 58-59 (U.S. Military Commission, Augsberg, Germany, Jun. 13,
1945) (rejecting military necessity as a defense to the murder of a prisoner of war); United States v. Milch, II TRIALS
OF WAR CRIMINALS BEFORE THE NMT 849-50 (Musmanno, J., concurring) (rejecting defense counsel argument that
“total warfare” allowed suspension or abrogation of law of war rules).
27 1956 FM 27-10 (Change No. 1 1976) ¶3a (“Military necessity has been generally rejected as a defense for acts
forbidden by the customary and conventional laws of war inasmuch as the latter have been developed and framed
with consideration for the concept of military necessity.”); United States v. Krupp, et al., IX TRIALS OF WAR
CRIMINALS BEFORE THE NMT 1347 (“In short these rules and customs of warfare are designed specifically for all
phases of war. They comprise the law for such emergency.”); Treaty of Amity and Commerce between His Majesty
the King of Prussia and the United States of America, art. 24, Sept. 10, 1785, 18 STAT. 641, 647 (declaring that
“neither the pretence that war dissolves all treaties, nor any other whatever, shall be considered as annulling or
suspending this and next preceding article; but on the contrary, that the state of war is precisely that for which they
are provided, and during which they are to be as sacredly observed as the most acknowledged articles in the law of
nature or nations.”).
28 See, e.g., HAGUE IV preamble ¶5 (“these provisions, the wording of which has been inspired by the desire to
diminish the evils of war, as far as military requirements permit, are intended to serve as a general rule of conduct
for the belligerents in their mutual relations and in their relations with the inhabitants.”) (emphasis added).
54
The fact that law of war rules are formulated specifically with military requirements in
mind has played an important part in the doctrine that the law of war is the lex specialis
governing armed conflict.29
2.2.2.2 Incorporation of Military Necessity Into Law of War Rules. Although
military necessity cannot justify actions that have been prohibited by the law of war, some law of
war rules expressly incorporate military necessity.
For example, certain law of war rules specify that departures from what would otherwise
be the rule are permissible when absolutely or imperatively necessary. In these cases, military
necessity must not be conflated with mere convenience.30 Examples of rules incorporating the
concept of absolute or imperative necessity include the following:
• The activities of the representatives or delegates of the Protecting Powers shall only be
restricted as an exceptional and temporary measure when this is rendered necessary by
imperative military necessities.31
• The internment or placing in assigned residence of protected persons may be ordered
only if the security of the Detaining Power makes it absolutely necessary.32
• If the Occupying Power considers it necessary, for imperative reasons of security, to take
safety measures concerning protected persons, it may, at the most, subject them to
assigned residence or to internment.33
• The seizure or destruction of enemy property must be imperatively demanded by the
necessities of war.34
Certain law of war rules may direct that persons comply with an obligation, but only to
the extent feasible or consistent with military necessity. Examples of rules incorporating the
concept of feasibility or necessity include the following:
29 Refer to § 1.3.2.1 (The Law of War as the Lex Specialis Governing Armed Conflict).
30 See United States v. List, et al. (The Hostage Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1252
(rejecting defendants’ “plea of military necessity, a term which they confuse with convenience and strategical
interests.”); General Dwight D. Eisenhower, Commander-in-Chief, U.S. Army, Memorandum Regarding the
Protection of Historical Monuments in Italy, Dec. 29, 1943, X WHITEMAN’S DIGEST 438 (§13) (explaining that
although “the phrase ‘military necessity’ is sometimes used where it would be more truthful to speak of military
convenience or even personal convenience,” military necessity should not “cloak slackness or indifference” to
discerning whether law of war obligations, such as the protection of cultural property, may be fulfilled without any
detriment to operational needs).
31 Refer to § 4.25.3 (Restrictions on Representatives of the Protecting Powers).
32 Refer to § 10.9.2.1 (Internment or Assigned Residence Only if Absolutely Necessary).
33 Refer to § 10.9.3.1 (Internment or Assigned Residence for Imperative Reasons of Security).
34 Refer to § 5.17.2 (Enemy Property - Military Necessity Standard); § 11.18.2 (Seizure or Destruction of Property
During Occupation - Application of the Military Necessity Standard).
55
• Certain affirmative duties to take feasible precautions to reduce the risk of harm to the
civilian population and other protected persons and objects.35
• Military medical and religious personnel, if their retention is not indispensable, are to be
returned to the party to the conflict to which they belong as soon as a road is open for
their return and military requirements permit.36
• Whenever military considerations permit, POW camps shall be indicated in the day time
by the letters PW or PG, placed so as to be clearly visible from the air.37
• Should military necessity require the quantity of relief shipments to civilian internees to
be limited, due notice thereof shall be given to the Protecting Power and to the
International Committee of the Red Cross, or to any other organization giving assistance
to the internees and responsible for the forwarding of such shipments.38
2.2.3 Applying Military Necessity. Military necessity is a difficult concept to define and
apply.39 What is necessary in war may depend closely on the specific facts and circumstances of
a given situation, and different people often assess military necessity differently. The limited and
unreliable nature of information available during war compounds this difficulty in evaluating
what is necessary.40 This difficulty runs throughout the law of war, since military necessity is
itself important and is an element of many other principles and rules.
The law of war seeks to ameliorate these difficulties in applying military necessity by:
(1) permitting consideration of the broader imperatives of winning the war as quickly and
efficiently as possible; (2) recognizing that certain types of actions are, as a general matter,
inherently militarily necessary; and (3) recognizing that persons must assess the military
necessity of an action in good faith based on the information available to them at the relevant
time and that they cannot be judged based on information that subsequently comes to light.
2.2.3.1 Consideration of the Broader Imperatives of Winning the War. In
evaluating military necessity, one may consider the broader imperatives of winning the war as
quickly and efficiently as possible and is not restricted to considering only the demands of the
specific situation.
This is the case because military necessity justifies those measures necessary to achieve
the object of war, and the object of war is not simply to prevail, but to prevail as quickly and
35 Refer to § 5.3.3 (Affirmative Duties to Take Feasible Precautions for the Protection of Civilians and Other
Protected Persons and Objects).
36 Refer to § 7.9.4 (Return of Personnel Whose Retention Is Not Indispensable).
37 Refer to § 9.11.4.3 (Marking of POW Camps).
38 Refer to § 10.23.3 (Receipt of Individual and Collective Relief Shipments for Internees).
39 See SPAIGHT, WAR RIGHTS ON LAND 113 (“There is no conception in International Law more elusive, protean,
wholly unsatisfactory, than that of war necessity.”).
40 Refer to § 1.4.2.2 (Nature of War - Limited and Unreliable Information - “Fog of War”).
56
efficiently as possible.41 Thus, military necessity may consider the broader imperatives of
winning the war and not only the demands of the immediate situation. For example, in assessing
the military advantage of attacking an object, one may consider the entire war strategy rather
than only the potential tactical gains from attacking that object.42 An interpretation of military
necessity that only permitted consideration of the immediate situation could prolong the fighting
and increase the overall suffering caused by the war.43
Some commentators have argued that military necessity should be interpreted so as to
permit only what is actually necessary in the prevailing circumstances, such as by requiring
commanders, if possible, to seek to capture or wound enemy combatants rather than to make
them the object of attack.44 This interpretation, however, does not reflect customary
international law or treaty law applicable to DoD personnel.45 For example, the law of war does
not require that enemy combatants be warned before being made the object of attack, nor does
the law of war require that enemy combatants be given an opportunity to surrender before being
41 Refer to § 1.4.1 (Object of War).
42 Refer to § 5.7.7.3 (Definite Military Advantage); § 5.12.5 (“Concrete and Direct Military Advantage Expected to
Be Gained”).
43 See, e.g., Department of Defense, National Military Strategy of the United States, 10 (Jan. 1992) (“Once a
decision for military action has been made, half-measures and confused objectives extract a severe price in the form
of a protracted conflict which can cause needless waste of human lives and material resources, a divided nation at
home, and defeat. Therefore, one of the essential elements of our national military strategy is the ability to rapidly
assemble the forces needed to win -- the concept of applying decisive force to overwhelm our adversaries and
thereby terminate conflicts swiftly with a minimum loss of life.”); LIEBER CODE art. 29 (“The more vigorously wars
are pursued, the better it is for humanity. Sharp wars are brief.”); Count von Moltke, letter to Professor Bluntschli,
Dec. 11, 1880, reprinted in G. SHERSTON BAKER, II HALLECK’S INTERNATIONAL LAW 19 footnote 1 (1908) (“The
greatest kindness in war is to bring it to a speedy conclusion.”).
44 See, e.g., Nils Melzer, Legal Adviser, International Committee of the Red Cross, Interpretive Guidance on the
Notion of Direct Participation in Hostilities Under International Humanitarian Law, 79 (May 2009) (“In
conjunction, the principles of military necessity and of humanity reduce the sum total of permissible military action
from that which IHL does not expressly prohibit to that which is actually necessary for the accomplishment of a
legitimate military purpose in the prevailing circumstances.”) (emphasis added); JEAN PICTET, DEVELOPMENT AND
PRINCIPLES OF INTERNATIONAL HUMANITARIAN LAW 75-76 (1985) (“If we can put a soldier out of action by
capturing him, we should not wound him; if we can obtain the same result by wounding him, we must not kill
him.”).
45 See, e.g., W. Hays Parks, Chief, International Law Branch, Office of the Judge Advocate General, Department of
the Army, Executive Order 12333 and Assassination, Nov. 2, 1989, III CUMULATIVE DIGEST OF UNITED STATES
PRACTICE IN INTERNATIONAL LAW 1981-1988 3411, 3419 (“In the employment of military forces, the phrase
‘capture or kill’ carries the same meaning or connotation in peacetime as it does in wartime. There is no obligation
to attempt capture rather than attack of an enemy. In some cases, it may be preferable to utilize ground forces in
order to capture, e.g., a known terrorist. However, where the risk to U.S. forces is deemed too great, if the President
has determined that the individual[s] in question pose such a threat to U.S. citizens or the national security interests
of the United States as to require the use of military force, it would be legally permissible to employ, e.g., an
airstrike against that individual or group rather than attempt his, her, or their capture, and would not violate the
prohibition on assassination.”).
57
made the object of attack.46 Moreover, the law of war may justify the use of overwhelming force
against enemy military objectives.47
2.2.3.2 Recognizing Certain Types of Actions as Generally Inherently Militarily
Necessary. The law of war recognizes that certain types of actions are, as a general matter,
inherently militarily necessary.48 For example, attacking enemy combatants is generally
lawful.49 Similarly, the internment of enemy POWs is generally lawful.50 Such rules may be
viewed as an example of how, when specific rules are applicable, there is less need to resort to
fundamental law of war principles as a general guide for conduct during war.51
2.2.3.3 Good Faith Evaluation of Military Necessity Based on the Available
Information. In what is sometimes called the “Rendulic Rule,” the law of war recognizes that
persons must assess the military necessity of an action based on the information available to
them at that time; they cannot be judged based on information that subsequently comes to light.52
2.3 HUMANITY
Humanity may be defined as the principle that forbids the infliction of suffering, injury,
or destruction unnecessary to accomplish a legitimate military purpose.53
2.3.1 Humanity as a Prohibition. Although military necessity justifies certain actions
necessary to defeat the enemy as quickly and efficiently as possible, military necessity cannot
46 Refer to § 5.5.6.1 (Surprise Attacks); § 5.5.6.2 (Attacks on Retreating Forces).
47 Refer to § 5.5.6 (Force That May Be Applied Against Military Objectives).
48 See VATTEL, THE LAW OF NATIONS 295 (3.9.173) (explaining that the law of war seeks to avoid contentious
disputes between belligerents about whether actions are militarily necessary by establishing “general rules
independent of circumstances and of certain and easy application” and thus “permits or tolerates every act which in
its essential nature is adapted to attaining the end of war; and it does not stop to consider whether the act was
unnecessary, useless, or superfluous in a given case unless there is the clearest evidence that an exception should be
made in that instance”).
49 Refer to § 5.6.1 (Persons, Objects, and Locations That Are Not Protected From Being Made the Object of Attack).
50 Refer to § 9.11.1 (Internment in POW Camps).
51 Refer to § 2.1.2.2 (Law of War Principles as a General Guide).
52 Refer to § 5.4 (Assessing Information Under the Law of War).
53 See, e.g., 2001 CANADIAN MANUAL ¶202(6) (humanity “forbids the infliction of suffering, injury or destruction
not actually necessary for the accomplishment of legitimate military purposes.”); 2004 UK MANUAL ¶2.4
(“Humanity forbids the infliction of suffering, injury, or destruction not actually necessary for the accomplishment
of legitimate military purposes.”); GREENSPAN, MODERN LAW OF LAND WARFARE 315 (humanity “forbids the
employment of all such kinds and degrees of violence as are not necessary for the purpose of the war”); 1958 UK
MANUAL ¶3 (humanity is the principle “according to which kinds and degrees of violence which are not necessary
for the purpose of war are not permitted to a belligerent;”); LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW
227 (§67) (Humanity “postulates that all such kinds and degrees of violence as are not necessary for the
overpowering of the opponent should not be permitted to a belligerent.”); 1940 RULES OF LAND WARFARE ¶4b
(defining the principle of humanity as “prohibiting employment of any such kind or degree of violence as is not
actually necessary for the purpose of the war”); 1914 RULES OF LAND WARFARE ¶9 (The principle of humanity
“says that all such kinds and degrees of violence as are not necessary for the purpose of war are not permitted to a
belligerent.”).
58
justify actions not necessary to achieve this purpose, such as cruelty or wanton violence.54
Moreover, once a military purpose has been achieved, inflicting more suffering is unnecessary
and should be avoided. For example, if an enemy combatant has been placed hors de combat
(e.g., incapacitated by being severely wounded or captured), no military purpose is served by
continuing to attack him or her.55 Thus, the principle of humanity forbids making enemy
combatants who have been placed hors de combat the object of attack.56 Similarly, the principle
of humanity has been viewed as the source of the civilian population’s immunity from being
made the object of attack because their inoffensive and harmless character means that there is no
military purpose served by attacking them.57
2.3.1.1 Relationship Between the Principles of Humanity and Military Necessity
. Humanity is related to military necessity, and these principles logically complement
one another.
Humanity may be viewed as the logical inverse of the principle of military necessity. If
certain necessary actions are justified, then certain unnecessary actions are prohibited. The
principle of humanity is an example of how the concept of necessity can function as a limitation
as well as a justification.58
Because humanity forbids those actions that are unnecessary, the principle of humanity is
not in tension with military effectiveness, but instead reinforces military effectiveness.59
2.3.2 Humanity and Law of War Rules. Humanity animates certain law of war rules,
including:
• fundamental safeguards for persons who fall into the hands of the enemy;60
54 United States v. List, et al. (The Hostage Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1253-54
(“[Military necessity] does not permit the killing of innocent inhabitants for purposes of revenge or the satisfaction
of a lust to kill.
… It does not admit the wanton devastation of a district or the willful infliction of suffering upon its
inhabitants for the sake of suffering alone.”); LIEBER CODE art. 16 (“Military necessity does not admit to cruelty --
that is, the infliction of suffering for the sake of suffering or for revenge, … .”).
55 See 2004 UK MANUAL ¶2.4.1 (“The principle of humanity is based on the notion that once a military purpose has
been achieved, the further infliction of suffering is unnecessary. Thus, if an enemy combatant has been put out of
action by being wounded or captured, there is no military purpose to be achieved by continuing to attack him. For
the same reason, the principle of humanity confirms the basic immunity of civilian populations and civilian objects
from attack because civilians and civilian objects make no contribution to military action.”).
56 Refer to § 5.10 (Persons Placed Hors de Combat).
57 Refer to § 4.2.1 (Development of the Distinction Between the Armed Forces and the Civilian Population).
58 Cf. Ex parte Milligan, 71 U.S. 2, 127 (1866) (“If, in foreign invasion or civil war, the courts are actually closed,
and it is impossible to administer criminal justice according to law, then, on the theatre of active military operations,
where war really prevails, there is a necessity to furnish a substitute for the civil authority, thus overthrown, to
preserve the safety of the army and society, and as no power is left but the military, it is allowed to govern by
martial rule until the laws can have their free course. As necessity creates the rule, so it limits its duration, for, if
this government is continued after the courts are reinstated, it is a gross usurpation of power.”) (emphasis added).
59 Refer to § 18.2.1 (Reinforcing Military Effectiveness).
59
• protections for the civilian population and civilian objects;61
• protections for military medical personnel, units, and transports;62
• prohibitions on weapons that are calculated to cause superfluous injury;63 and
• prohibitions on weapons that are inherently indiscriminate.64
The principle of humanity may help interpret or apply these and other law of war rules.
For example, the requirement that POWs be interned only in premises located on land has been
understood not to prohibit POW detention aboard ships pending the establishment of suitable
facilities on land, if detention aboard ships provides the most appropriate living conditions for
POWs.65 Similarly, the U.S. reservation to CCW Protocol III on Incendiary Weapons makes
clear that U.S. forces may use incendiary weapons against military objectives located in
concentrations of civilians where it is judged that such use would cause fewer casualties and/or
less collateral damage than alternative weapons.66
2.4 PROPORTIONALITY
Proportionality may be defined as the principle that even where one is justified in acting,
one must not act in way that is unreasonable or excessive.67
Proportionality has also been viewed as a legal restatement of the military concept of
economy of force.68
60 Refer to § 8.2 (Humane Treatment of Detainees); § 9.5 (Humane Treatment and Basic Protections for POWs);
§ 10.5 (Humane Treatment and Other Basic Protections for Protected Persons).
61 Refer to § 5.3 (Overview of Rules for the Protection of Civilians).
62 Refer to § 7.8 (Respect and Protection of Categories of Medical and Religious Personnel); § 7.10 (Military
Medical Units and Facilities); § 7.11 (Ground Transport); § 7.12 (Hospital Ships, Sick-Bays in Warships, and
Coastal Rescue Craft); § 7.14 (Military Medical Aircraft).
63 Refer to § 6.6 (Weapons Calculated to Cause Superfluous Injury).
64 Refer to § 6.7 (Inherently Indiscriminate Weapons).
65 Refer to § 9.11.3.1 (Location on Land).
66 Refer to § 6.14.3.2 (U.S. Reservation to CCW Protocol III on Incendiary Weapons).
67 See Daniel Webster, Letter to Mr. Fox, Apr. 24, 1841, reprinted in DANIEL WEBSTER, THE DIPLOMATIC AND
OFFICIAL PAPERS OF DANIEL WEBSTER, WHILE SECRETARY OF STATE 110 (1848) (explaining that even actions taken
in self-defense should not be “unreasonable or excessive” since such actions “justified by the necessity of self-
defense, must be limited by that necessity and kept clearly within it”). See also GROTIUS, LAW OF WAR & PEACE
601 (3.1.4.2) (“we must also beware of what happens, and what we foresee may happen, beyond our purpose, unless
the good which our action has in view is much greater than the evil which is feared, or, greater than the fear of the
evil.”); VATTEL, THE LAW OF NATIONS 279 (3.8.137) (explaining that a Sovereign has “the right to make war upon
his fellow-men as a matter of necessity, and as a remedy,” but the Sovereign should not “push the remedy beyond its
just limits,” and should “be careful not to make it more severe or more disastrous to mankind than the care of his
own safety and the defense of his rights require.”).
60
2.4.1 Proportionality as a Limit on the Exercise of a Right.
2.4.1.1 Justification in Acting. Proportionality addresses cases in which one is
justified in acting. In jus in bello, the justification at issue generally is military necessity. So, for
example, an attack on enemy soldiers that incidentally damages civilian property would trigger
proportionality considerations. On the other hand, where there is no justification for acting, such
as unlawful attacks directed against the civilian population, proportionality concerns would not
be reached.
2.4.1.2 Unreasonable or Excessive. Proportionality generally weighs the
justification for acting against the expected harms to determine whether the latter are
disproportionate in comparison to the former. In war, incidental damage to the civilian
population and civilian objects is unfortunate and tragic, but inevitable.69 Thus, applying the
proportionality rule in conducting attacks does not require that no incidental damage result from
attacks. Rather, this rule obliges persons to refrain from attacking where the expected harm
incidental to such attacks would be excessive in relation to the military advantage anticipated to
be gained.70
Under the law of war, judgments of proportionality often involve difficult and subjective
comparisons.71 Recognizing these difficulties, States have declined to use the term
“proportionality” in law of war treaties because it could incorrectly imply an equilibrium
between considerations or suggest that a precise comparison between them is possible.72
2.4.2 Proportionality and the Law of War. The principle of proportionality is reflected in
many areas in the law of war.
Proportionality most often refers to the jus in bello standard applicable to persons
conducting attacks.73 Proportionality considerations, however, may also be understood to apply
to the party subject to attack, which must take feasible precautions to reduce the risk of
68 General George S. Brown, Chairman of the Joint Chiefs of Staff, Address: Duke University School of Law, Oct.
10, 1974, reprinted in ADDRESSES AND STATEMENTS BY GENERAL GEORGE S. BROWN, USAF, CHAIRMAN, JOINT
CHIEF OF STAFF 1974-1978 (1978) (“We recognize that wanton destruction and unnecessary suffering are both
violations of these military developed legal principles and counterproductive to the political military goals of the
Nation. The law of ‘proportionality’ is simply a legal restatement of the time honored military concept of ‘economy
of force.’”).
69 Refer to § 1.4.2 (Nature of War).
70 Refer to § 5.12 (Proportionality in Conducting Attacks).
71 Refer to § 5.12.4 (“Excessive”). Compare § 2.2.3 (Applying Military Necessity).
72 See, e.g., BOTHE, PARTSCH, & SOLF, NEW RULES 309-10 (AP I art. 51, ¶2.6.2) (describing how some government
delegations in the 1974-1977 Diplomatic Conference opposed incorporation of the term “proportionality” or
acknowledgement of a law of war “rule” of proportionality in AP I and AP II).
73 Refer to § 5.12 (Proportionality in Conducting Attacks).
61
incidental harm.74 Proportionality also plays a role in assessing whether weapons are prohibited
because they are calculated to cause unnecessary suffering.75
In jus ad bellum, proportionality requires that the State’s means in resorting to force be
proportionate to its just cause in using force, such as the threat that the State seeks to address.76
Proportionality is also a requirement for reprisals, which must respond in a proportionate manner
to the preceding illegal act by the party against which they are taken.77
2.5 DISTINCTION
Distinction, sometimes called discrimination, obliges parties to a conflict to distinguish
principally between the armed forces and the civilian population, and between unprotected and
protected objects.78
Distinction may be understood as encompassing two sets of reinforcing duties. Parties to
a conflict must apply a framework of legal classes for persons and objects by: (1) discriminating
in conducting attacks against the enemy; and (2) distinguishing a party’s own persons and
objects.
2.5.1 Distinction as a Framework of Legal Classes. Distinction requires parties to a
conflict to apply a framework of legal classes for persons and objects, each class characterized
by different rights, duties, and liabilities.
Principally, distinction seeks to separate the armed forces and the civilian population.79
There are, however, certain special cases, such as military medical and religious personnel, who
may be treated like a combatant for one purpose (e.g., detention) but like a civilian for another
74 Refer to § 5.14 (Feasible Precautions to Reduce the Risk of Harm to Protected Persons and Objects by the Party
Subject to Attack).
75 Refer to § 6.6.3.3 (Clearly Disproportionate).
76 Refer to § 1.11.1.2 (The Means Must Be Proportionate to the Just Cause (Proportionality - Jus ad Bellum)).
77 Refer to § 18.18.2.4 (Proportionality in Reprisal).
78 See, e.g., J. Fred Buzhardt, DoD General Counsel, Letter to Senator Edward Kennedy, Sept. 22, 1972, reprinted in
67 AJIL 122 (1973) (“A summary of the laws of armed conflict, in the broadest terms, reveals certain general
principles including the following: … (c). That a distinction must be made at all times between persons taking part
in the hostilities and members of the civilian population to the effect that the civilians be spared as much as possible.
These general principles were recognized in a resolution unanimously adopted by the United Nations General
Assembly in its Resolution dated 13 January 1969 (Resolution 2444 (XXIII)). We regard them as declaratory of
existing customary international law.”); Ex parte Quirin, 317 U.S. 1, 30 (1942) (“By universal agreement and
practice, the law of war draws a distinction between the armed forces and the peaceful populations of belligerent
nations,”); 2004 UK MANUAL ¶2.5 (“Since military operations are to be conducted only against the enemy’s armed
forces and military objectives, there must be a clear distinction between the armed forces and civilians, or between
combatants and non-combatants, and between objects that might legitimately be attacked and those that are
protected from attack.”). Consider AP I art. 48 (“In order to ensure respect for and protection of the civilian
population and civilian objects, the Parties to the conflict shall at all times distinguish between the civilian
population and combatants and between civilian objects and military objectives and accordingly shall direct their
operations only against military objectives.”).
79 Refer to § 4.2 (The Armed Forces and the Civilian Population).
62
purpose (e.g., not being made the object of attack).80 However, for any particular legal purpose,
a person may not claim the distinct rights afforded to both combatants and civilians at the same
time.81
2.5.2 Discriminating in Conducting Attacks Against the Enemy. Distinction requires
parties to a conflict to discriminate in conducting attacks against the enemy.82 On the one hand,
consistent with military necessity, parties may make enemy combatants and other military
objectives the object of attack.83 On the other hand, consistent with humanity, parties may not
make the civilian population and other protected persons and objects the object of attack.84
Moreover, persons using force must discriminate between legitimate and illegitimate objects of
attack in good faith based on the information available to them at the time.85
2.5.3 Distinguishing a Party’s Own Persons and Objects. Distinction enjoins the party
controlling the population86 to use its best efforts to distinguish or separate its military forces and
war-making activities from members of the civilian population to the maximum extent feasible
so that civilian casualties and damage to civilian objects incidental to attacks on military
objectives will be minimized as much as possible.87
Parties to a conflict must:
(1) take certain measures to help ensure that military forces
and civilians can be visually distinguished from one another; (2) physically separate, as feasible,
their military objectives from the civilian population and other protected persons and objects;
and (3) refrain from the misuse of protected persons and objects to shield military objectives.
2.5.3.1 Measures to Help Ensure That Military Forces and Civilians Are Visually
Distinguishable From One Another. Parties to a conflict must take certain measures, in offense
or defense, to help ensure that military forces and civilians can be visually distinguished from
one another.
80 Refer to § 4.2.3 (Mixed Cases).
81 Refer to § 4.2.2 (No Person May Claim the Distinct Rights Afforded to Both Combatants and Civilians at the
Same Time).
82 Refer to § 5.6 (Discrimination in Conducting Attacks).
83 Refer to § 5.6.1 (Persons, Objects, and Locations That Are Not Protected From Being Made the Object of Attack).
84 Refer to § 5.6.2 (Persons, Objects, and Locations That Are Protected From Being Made the Object of Attack).
85 Refer to § 5.4 (Assessing Information Under the Law of War).
86 Refer to § 5.3.1 (Responsibility of the Party Controlling Civilian Persons and Objects).
87 See J. Fred Buzhardt, DoD General Counsel, Letter to Senator Edward Kennedy, Sept. 22, 1972, reprinted in 67
AJIL 122 (1973) (“A summary of the laws of armed conflict, in the broadest terms, reveals certain general principles
including the following: … (c). That a distinction must be made at all times between persons taking part in the
hostilities and members of the civilian population to the effect that the civilians be spared as much as possible. …
The principle in (c) addresses primarily the Party exercising control over members of the civilian population. This
principle recognizes the interdependence of the civilian community with the overall war effort of a modern society.
But its application enjoins the party controlling the population to use its best efforts to distinguish or separate its
military forces and war making activities from members of the civilian population to the maximum extent feasible
so that civilian casualties and damage to civilian objects incidental to attacks on military objectives, will be
minimized as much as possible.”).
63
First, parties to a conflict must not disguise their armed forces as civilians or as other
protected categories of persons in order to kill or wound opposing forces.88 Second, other rules
obligate parties to mark protected persons and objects to help ensure they receive the protections
of that status.89 Third, certain rules encourage parties to a conflict to identify certain persons and
objects as unprotected. For example, during international armed conflict, members of organized
resistance movements must, inter alia, wear fixed distinctive signs visible at a distance and carry
arms openly to distinguish themselves from the civilian population in order for members of their
group to receive POW status.90
2.5.3.2 Feasible Measures to Separate Physically a Party’s Own Military
Objectives From the Civilian Population and Other Protected Persons and Objects. Distinction
also creates obligations for parties to a conflict to take feasible measures to separate physically
their own military objectives from the civilian population and other protected persons and
objects.91
For example, it may be appropriate to evacuate civilians from danger areas.92 Similarly,
if feasible, military commanders should avoid placing military objectives in densely populated
areas.93 In addition, it may be appropriate to establish zones where civilians and other protected
persons may seek refuge.94
2.5.3.3 Refrain From the Misuse of Protected Persons and Objects to Shield
Military Objectives. Parties to a conflict must refrain from the misuse of civilians and other
protected persons and objects to shield their own military objectives.95 For example, it is
prohibited to take hostages or otherwise to endanger deliberately protected persons or objects for
the purpose of deterring enemy military operations.
Misusing protected persons and objects to shield military objectives also offends honor
because it constitutes a breach of trust with the enemy and thus undermines respect for the law of
war.96
2.5.4 Misconceptions About Distinction. Distinction seeks to ensure that protected and
unprotected categories are distinct from one another, not distinct in the abstract. For example,
using camouflage is consistent with distinction because foliage is not a protected category and
88 Refer to § 5.22 (Treachery or Perfidy Used to Kill or Wound).
89 Refer to § 5.14.4 (Using Distinctive and Visible Signs to Identify Protected Persons and Objects as Such).
90 Refer to § 4.6.4 (Having a Fixed Distinctive Sign Recognizable at a Distance); § 4.6.5 (Carrying Arms Openly).
91 Refer to § 5.14 (Feasible Precautions to Reduce the Risk of Harm to Protected Persons and Objects by the Party
Subject to Attack).
92 Refer to § 5.14.2 (Removing Civilians and Civilian Objects From the Vicinity of Military Objectives).
93 Refer to § 5.14.1 (Refraining From Placing Military Objectives in Densely Populated Areas).
94 Refer to § 5.14.3 (Establishing Areas Where Civilians or the Wounded and Sick Are Protected).
95 Refer to § 5.16 (Prohibition on Using Protected Persons and Objects to Shield, Favor, or Impede Military
Operations).
96 Refer to § 2.6.2 (Certain Amount of Fairness in Offense and Defense).
64
because civilians generally do not wear camouflage.97 Similarly, U.S. forces have worn non-
standard uniforms to blend with local forces while remaining distinct from the civilian
population.98
Distinction addresses the different rights, duties, and liabilities of the categories; it does
not require that a particular person or object fall within a particular category. For example, the
principle of distinction does not prohibit an otherwise civilian object from being used for military
purposes, thereby turning it into a military objective.99 However, if such an object were seized
from the enemy, such seizure would have to have been imperatively demanded by the necessities
of war.100 Similarly, persons with medical training or who provide medical care on the
battlefield are not necessarily military medical personnel and need not be identified as such.101
Rather, a State may reserve the ability to use these persons as combatants by refraining from
designating them as exclusively engaged in medical activities.
2.5.5 Reinforcing Duties - Discriminating in Conducting Attacks and Distinguishing a
Party’s Own Persons and Objects. Discriminating in conducting attacks against the enemy and
distinguishing a party’s own persons and objects reinforce one another.
A party is not relieved of its obligations to discriminate in conducting attacks by the
failures of its adversary to distinguish its military objectives from protected persons and
objects.102 Nonetheless, the practical ability of a party to a conflict to discriminate in conducting
attacks often depends on the degree to which its enemy has distinguished its military objectives
from its protected persons and objects. For example, if enemy forces intermingle with civilians,
then a party may be less able to avoid incidentally harming the civilian population.
In addition, the degree to which an enemy force in fact discriminates in conducting
attacks may affect whether a party distinguishes its protected persons and objects from its
military objectives. For example, if enemy forces do not respect the red cross emblem, but
instead specifically attack persons wearing it, then the party receiving these attacks is less likely
to distinguish its medical personnel and transports.103 Similarly, if insurgents seek to attack
civilians in a non-international armed conflict, positioning military forces near the civilian
population may be essential to protecting the civilian population.104
97 Refer to § 5.25.2 (Examples of Ruses), footnote 700 and accompanying text.
98 Refer to § 5.25.2.1 (Mimicking Other Friendly Forces).
99 Refer to § 5.16.1 (Protected Persons and Objects).
100 Refer to § 5.17.2.2 (Seizure or Destruction of Enemy Property to Support Military Operations).
101 Refer to § 4.9.2 (Requirements for Military Medical and Religious Status).
102 Refer to § 5.5.4 (Failure by the Defender to Separate or Distinguish Does Not Relieve the Attacker of the Duty to
Discriminate in Conducting Attacks).
103 Refer to § 7.15.2.1 (Removal or Obscuration of the Distinctive Emblem).
104 Refer to § 17.5.2.1 (Positioning Military Forces Near the Civilian Population to Win Their Support and to Protect
Them).
65
2.6 HONOR
Honor demands a certain amount of fairness in offense and defense and a certain mutual
respect between opposing forces.105
2.6.1 Honor - Background and Notes on Terminology. Honor has been vital to the
development of the law of war, which was preceded by warriors’ codes of honor.106 Honor
continues to be vital to giving the law of war effect today.
Honor is also called chivalry. Chivalry is often associated with a specific historical
context—a code of behavior for knights in Europe during the Middle Ages. Honor may be more
readily understood as incorporating warriors’ codes from a variety of cultures and time periods.
2.6.2 Certain Amount of Fairness in Offense and Defense. Honor requires a certain
amount of fairness in offense and defense. Honor forbids resort to means, expedients, or conduct
that would constitute a breach of trust with the enemy.107
2.6.2.1 Acceptance That Belligerent Rights Are Not Unlimited. In requiring a
certain amount of fairness in offense and defense, honor reflects the principle that parties to a
conflict must accept that certain limits exist on their ability to conduct hostilities. For example,
parties to the conflict must accept that the right of belligerents to adopt means of injuring the
enemy is not unlimited.108 Here, honor does not address what those limits are so much as
requires that parties accept that there are legal limits that govern their conduct of hostilities.109
105 See, e.g., LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW 227 (§67) (chivalry “arose in the Middle Ages
and introduced a certain amount of fairness in offence and defence, and a certain mutual respect”); 1958 UK
MANUAL ¶3 (“The development of the law of war has been determined by three principles: … and thirdly, the
principle of chivalry, which demands a certain amount of fairness in offence and defence, and a certain mutual
respect between the opposing forces.”); 1914 RULES OF LAND WARFARE ¶9 (“The development of the laws and
usages of war is determined by three principles. … Third, the principle of chivalry, which demands a certain amount
of fairness in offense and defense and a certain mutual respect between opposing forces.”); UNITED KINGDOM WAR
OFFICE, MANUAL OF MILITARY LAW, Chapter XIV, The Laws and Usages of War on Land, 234 (¶3) (1914) (“The
development of the laws and usages of war is determined by three principles. … And there is, thirdly, the principle
of chivalry, which demands a certain amount of fairness in offence and defence, and a certain mutual respect
between the opposing forces.”).
106 See, e.g., LESLIE C. GREEN, THE CONTEMPORARY LAW OF ARMED CONFLICT 20-23 (2000) (describing references
to warrior codes from ancient Israel, China, India, Greece, Rome, and Islam).
107 1940 RULES OF LAND WARFARE ¶4(c) (chivalry “denounces and forbids resort to dishonorable means,
expedients, or conduct”); 2001 CANADIAN MANUAL ¶202(7) (“An armed conflict is rarely a polite contest.
Nevertheless, the concept of chivalry is reflected in specific prohibitions such as those against dishonourable or
treacherous conduct and against misuse of enemy flags or flags of truce.”).
108 See, e.g., 1899 HAGUE II REG. art. 22 (“The right of belligerents to adopt means of injuring the enemy is not
unlimited.”); HAGUE IV REG. art. 22 (same); CCW preamble (noting “the principle of international law that the right
of the parties to an armed conflict to choose methods or means of warfare is not unlimited”). Consider AP I art.
35(1) (“In any armed conflict, the right of the Parties to the conflict to choose methods or means of warfare is not
unlimited.”).
109 Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. 583, 585 (¶11) (Dissenting
Opinion of Judge Higgins) (“The legal principle by which parties to an armed conflict do not have an unlimited
choice of weapons or of methods of warfare… [is intended] to ensure that weapons, both in the context of their use,
and in the methods of warfare, must comply with the other substantive rules.”).
66
This acceptance is a prerequisite for the existence and operation of the law of war in the way that
the principle of pacta sunt servanda (treaties are binding on parties and must be performed by
them in good faith) provides a necessary foundation for treaties to exist and operate as
instruments that are legally binding on States.110
Thus, honor may be understood to provide a foundation for obligations that help enforce
and implement the law of war or special agreements between belligerents during armed
conflict.111 For example, honor may be understood to provide the foundation for the requirement
for persons to comply with the law of war in good faith.112 Similarly, POWs are bound to adhere
to paroles on their personal honor.113
2.6.2.2 Prohibition on Conduct That Breaches Trust With the Enemy. In
requiring a certain amount of fairness in offense and defense, honor also forbids resort to means,
expedients, or conduct that would constitute a breach of trust with the enemy. In particular,
honor requires a party to a conflict to refrain from taking advantage of its opponent’s adherence
to the law by falsely claiming the law’s protections.
Honor forbids such conduct because it may: (1) undermine the protections afforded by
the law of war; (2) impair non-hostile relations between opposing belligerents; and (3) damage
the basis for the restoration of peace short of complete annihilation of one belligerent by
another.114
For example, enemies must deal with one another in good faith in their non-hostile
relations.115 And even in the conduct of hostilities, good faith prohibits:
(1) killing or wounding
enemy persons by resort to perfidy; (2) misusing certain signs; (3) fighting in the enemy’s
uniform; (4) feigning non-hostile relations in order to seek a military advantage; and (5)
compelling nationals of a hostile party to take part in the operations of war directed against their
own country.116 Honor, however, does not forbid parties from using ruses and other lawful
deceptions against which the enemy ought to take measures to protect itself.117
2.6.3 Certain Mutual Respect Between Opposing Forces. Honor demands a certain
mutual respect between opposing forces.
Opposing military forces should respect one another outside of the fighting because they
share a profession and they fight one another on behalf of their respective States and not out of
110 Refer to § 1.10.1.1 (Legal Force of Treaties Among States).
111 Refer to § 18.1.2 (National Obligations to Implement and Enforce the Law of War).
112 Refer to § 18.3 (Duties of Individual Members of the Armed Forces).
113 Refer to § 9.11.2 (Parole of POWs).
114 Refer to § 5.21.1 (Harms From Breaches of Good Faith).
115 Refer to § 12.2 (Principle of Good Faith in Non-Hostile Relations).
116 Refer to § 5.21 (Overview of Good Faith, Perfidy, and Ruses).
117 Refer to § 5.25 (Ruses of War and Other Lawful Deceptions).
67
personal hostility.118 For example, this principle is reflected in the rule that POWs are legally in
the hands of the enemy State and not the individuals or military units who have captured them.119
2.6.3.1 Honor and Rules for POW Captivity. In demanding a certain mutual
respect between opposing forces, honor animates rules that relate to the treatment of POWs. For
example, honor is one of the foundations for the humane treatment of POWs.120 The principle of
honor is also reflected in rules that require POWs and their captors to treat one another with
respect. For example, POWs must be treated with respect for their honor and person.121 As
another example, POWs, with the exception of officers, must salute and show to all officers of
the Detaining Power the external marks of respect provided for by the regulations applying in
their own forces.122 In addition, capitulations agreed upon between belligerents must take into
account the rules of military honor.123
2.6.3.2 Honor and the Class of Combatants. In demanding a certain mutual
respect between opposing forces, honor also reflects the premise that combatants are a common
class of professionals who have undertaken to comport themselves honorably.124
Honor thus animates the rules that determine who qualifies for privileges of combatant
status. For example, an armed group must, inter alia, be organized under a responsible
118 See JEAN-JACQUES ROUSSEAU, THE SOCIAL CONTRACT & DISCOURSES 12 (1920) (“The object of war being the
destruction of the hostile State, the other side has a right to kill its defenders, while they are bearing arms; but as
soon as they lay them down and surrender, they cease to be enemies or instruments of the enemy, and become once
more merely men, whose life no one has any right to take.”).
119 Refer to § 9.2.2 (Responsibility of the Detaining Power).
120 See, e.g., Samuel Falle, Chivalry, 113 Proceedings Magazine, Jan. 1987 (“During World War II, the Japanese
were portrayed as brutal, subhuman savages—the hordes of Attila or Genghis Khan. Certainly they did terrible
things, but I was fortunate enough to see something different. It is called ‘chivalry,’ which the Oxford Dictionary
defines as a ‘medieval knightly system, with its religious, moral, and social code; ideal knight’s characteristics.’ I
see it as compassion and magnanimity toward a beaten enemy.”); United States, et al. v. Göring, et al., Judgment, I
TRIAL OF THE MAJOR WAR CRIMINALS BEFORE THE IMT 289 (“When, on 8 September 1941, OKW issued its
ruthless regulations for Soviet POW’s, Canaris wrote to [the defendant] Keitel that under international law the SD
should have nothing to do with this matter. On this memorandum, in Keitel’s handwriting, dated 23 September and
initialed by him, is the statement:
‘The objections arise from the military concept of chivalrous warfare. This is the
destruction of an ideology. Therefore I approve and back the measures.’”).
121 Refer to § 9.5.1 (Respect for Their Persons and Honor).
122 Refer to § 9.22.3 (Saluting Between POWs and Officers of the Detaining Power).
123 Refer to § 12.8.3 (Rules of Military Honor).
124 SPAIGHT, AIR POWER AND WAR RIGHTS 109-10 (“Chivalry is difficult to define but it means broadly, the waging
of war in accordance with certain well-recognised formalities and courtesies. It is an influence quite distinct from
the humanitarian one; indeed, it prevailed in its full vigour at a time in which humanitarian interests were otherwise
entirely disregarded: witness the cruelty of the Black Prince to the people of Limoges. It is against free from any
necessary connection with Christianity; Saladin was a chivalrous as Coeur-de-Lion. It is, indeed, the spirit pure and
simple, of knighthood. It expresses in effect the feeling of the combatants that they belong to a caste, that their
encounter in arms is a high ceremonial, that an opponent is entitled to all honour and respect, that your enemy,
though he is your enemy, is at the same time a brother in the same noble family of knights-at-arms. Until
gunpowder came to democratise war, chivalry and chivalry alone was an influence making for moderation in war. It
was the first motive power for the creation of a restrictive law of war.”).
68
command and conduct its operations in accordance with the law of war in order for its members
to be entitled to POW status during international armed conflict.125 On the other hand, private
persons are generally denied the privileges of combatant status because they do not belong to this
class of combatants.126
The principle that combatants share a common class has also been a foundation for the
trial of enemy combatants by military tribunals.127 For example, the GPW expresses a
preference for POWs to be tried by military courts rather than civilian courts.128
125 Refer to § 4.6.1 (GPW 4A(2) Conditions in General).
126 Refer to § 4.18.3 (Private Persons Who Engage in Hostilities - Lack of the Privileges of Combatant Status).
127 General Douglas MacArthur, Action of the Confirming Authority, Feb. 7, 1946, United States v. Yamashita (U.S.
Military Commission, Manila, Dec. 7, 1945), LEVIE, DOCUMENTS ON POWS 298 (“It is not easy for me to pass penal
judgment upon a defeated adversary in a major military campaign. I have reviewed the proceedings in vain search
for some mitigating circumstance on his behalf. I can find none. Rarely has so cruel and wanton a record been
spread to public gaze. Revolting as this may be in itself, it pales before the sinister and far reaching implication
thereby attached to the profession of arms. The soldier, be he friend or foe, is charged with the protection of the
weak and unarmed. It is the very essence and reason for his being. When he violates this sacred trust, he not only
profanes his entire cult but threatens the very fabric of international society. The traditions of fighting men are long
and honorable. They are based upon the noblest of human traits, - sacrifice. This officer, of proven field merit,
entrusted with high command involving authority adequate to responsibility, has failed this irrevocable standard; has
failed his duty to his troops, to his country, to his enemy, to mankind; has failed utterly his soldier faith. The
transgressions resulting therefrom as revealed by the trial are a blot upon the military profession, a stain upon
civilization and constitute a memory of shame and dishonor that can never be forgotten. Peculiarly callous and
purposeless was the sack of the ancient city of Manila, with its Christian population and its countless historic shrines
and monuments of culture and civilization, which with campaign conditions reversed had previously been spared.”).
128 Refer to § 9.26.3 (Trial by Military Courts).
69
III - Application of the Law of War
Chapter Contents
3.1 Introduction
3.2 Situations to Which the Law of War Applies
3.3 Status of the Parties and the Law of War
3.4 When Jus in Bello Rules Apply
3.5 Relationship Between Jus in Bello and Jus ad Bellum
3.6 Reciprocity and Law of War Rules
3.7 Applying Rules by Analogy
3.8 End of Hostilities and the Application of the Law of War
3.9 Law of War Duties Also Applicable in Peace
3.1 INTRODUCTION
Whether a particular law of war rule applies to a situation may depend on a variety of
issues, such as (1) whether a state of “war,” “hostilities,” or “armed conflict” exists;1 (2) whether
a party is recognized as a belligerent or as a State;2 or (3) whether an enemy State has accepted
that law of war rule.3 This Chapter addresses these and other broad issues underlying the
application of law of war rules. Later chapters address issues in applying specific rules,
including considerations specific to those rules. For example, whether a specific provision of the
GPW applies to a particular person may depend on whether that person is entitled to POW status
under the GPW.4
Many of the legal issues underlying the application of law of war rules may be confusing
because they are complex and may appear to result in contradictory legal positions. For
example, a State may be at “war” for some purposes, but not for other purposes.5 The legal
character of U.S. military operations may change rapidly. For example, some operations may
begin as military operations other than war and later evolve into war, or an international armed
conflict may change into a non-international armed conflict.
Although this Chapter addresses how rules apply as a matter of law, DoD practice has
often been to act consistently with law of war rules, even in certain cases where these rules might
not technically be applicable as a matter of law.
1 Refer to § 3.4 (When Jus in Bello Rules Apply).
2 Refer to § 3.3 (Status of the Parties and the Law of War).
3 Refer to § 3.6.1 (Treaty Provisions That Provide for Reciprocity in the Scope of Application of the Treaty).
4 Refer to § 9.3 (POW Status).
5 Refer to § 1.5 (“War” as a Legal Concept).
70
3.1.1 DoD Practice of Applying Law of War Rules Even When Not Technically
Applicable. DoD policy and doctrine make clear the importance of compliance with,
implementation of, and enforcement of the law of war.6
In addition, DoD practice has often been to act consistently with law of war rules, even in
certain cases where these rules might not technically be applicable as a matter of law. This
means, for example, that DoD practice has often been to act consistently with a particular law of
war treaty rule, even if that rule might not apply as a matter of treaty law. Moreover, DoD
practice has sometimes been to adhere to the standards in the law of war, even in situations that
do not constitute “war” or “armed conflict,” because these standards in the law of war reflect
legal standards that must be adhered to in all circumstances (i.e., whether there is a state of
armed conflict or not).
3.1.1.1 Reasons for Acting Consistent With a Treaty Rule, Even Though the
Treaty Does Not Apply. DoD practice has often been to act consistently with a treaty rule, even
if that rule might not apply as a matter of treaty law. First, it may be appropriate to act
consistently with the terms of a treaty (even as applied in dealings with a non-Party to a treaty)
because the general principles of the treaty have been determined to be declaratory of customary
international law.7 In such cases, practice that is consistent with the treaty’s terms with regard to
a particular matter likewise would be in compliance with applicable customary international law.
In addition, it may be important to act consistently with the terms of the treaty because
the treaty represents “modern international public opinion” as to how military operations should
be conducted.8 Other policy considerations, including efficacious training standards or close
relations with coalition partners, may lead to a policy decision that DoD practice should be
consistent with a particular law of war treaty rule, even if that rule does not apply to U.S. forces
as a matter of law.
3.1.1.2 Applying Law of War Standards as Reflecting Minimum Legal Standards.
DoD practice also has been to adhere to certain standards in the law of war, even in situations
that do not constitute “war” or “armed conflict,” because these law of war rules reflect standards
that must be adhered to in all circumstances. Applying these standards provides assurance that
6 Refer to § 18.1.1 (DoD Policy on Implementing and Enforcing the Law of War).
7 1956 FM 27-10 (Change No. 1 1976) Foreword (“Moreover, even though States may not be parties to, or strictly
bound by, the 1907 Hague Conventions and the 1929 Geneva Convention relative to the Treatment of Prisoners of
War, the general principles of these conventions have been held declaratory of the customary law of war to which all
States are subject. For this reason, the United States has adopted the policy of observing and enforcing the terms of
these conventions in so far as they have not been superseded by the 1949 Geneva Conventions which necessarily
govern the relations between the parties to the latter (see pars. 6 and 7 of the text).”).
8 1956 FM 27-10 (Change No. 1 1976) ¶7a (“These treaty provisions are in large part but formal and specific
applications of general principles of the unwritten law. While solemnly obligatory only as between the parties
thereto, they may be said also to represent modern international public opinion as to how belligerents and neutrals
should conduct themselves in the particulars indicated. For these reasons, the treaty provisions quoted herein will be
strictly observed and enforced by United States forces without regard to whether they are legally binding upon this
country. Military commanders will be instructed which, if any, of the written rules herein quoted are not legally
binding as between the United States and each of the States immediately concerned, and which, if any, for that
reason are not for the time being to be observed or enforced.”).
71
the standards adhered to equal or exceed those required. This practice has been reflected in DoD
policies to comply with the law of war, or to comply with the spirit and principles of the law of
war, during military operations outside the context of armed conflict.9
Certain prohibitions and certain other rules in the law of war that reflect customary
international law have been described as reflecting “elementary considerations of humanity.”10
These “elementary considerations of humanity” have been understood to be “even more exacting
in peace than in war.”11 Thus, these legal standards, at a minimum, must be adhered to in all
circumstances.
In particular, Common Article 3 of the 1949 Geneva Conventions reflects a minimum
yardstick of humane treatment protections for all persons taking no active part in hostilities,
including members of armed forces who have laid down their arms and those placed hors de
combat by sickness, wounds, detention, or any other cause.12 The standards in Common Article
3 of the 1949 Geneva Conventions may be understood to reflect minimum humane treatment
standards for detainees in any military operation, including those during international or non-
international armed conflict or occupation, and those military operations that are not addressed
by the law of war. Additional rules will apply depending on the particular context. For example,
the United States has supported adherence to the guarantees in Article 75 of AP I during
international armed conflict.13
9 See DOD DIRECTIVE 2311.01E, DoD Law of War Program, ¶4.1 (May 9, 2006, Certified Current as of Feb. 22,
2011) (“Members of the DoD Components comply with the law of war during all armed conflicts, however such
conflicts are characterized, and in all other military operations.”); DOD DIRECTIVE 5100.77, DoD Law of War
Program, ¶5.3 (Dec. 9, 1998) (“The Heads of the DoD Components shall: 5.3.1. Ensure that the members of their
DoD Components comply with the law of war during all armed conflicts, however such conflicts are characterized,
and with the principles and spirit of the law of war during all other operations.”). Refer to § 18.1.1 (DoD Policy on
Implementing and Enforcing the Law of War).
10 Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. 226, 257 (¶79) (“It is
undoubtedly because a great many rules of humanitarian law applicable in armed conflict are so fundamental to the
respect of the human person and ‘elementary considerations of humanity’ as the Court put it in its Judgment of 9
April 1949 in the Corfu Channel case (I.C.J. Reports 1949, p. 22), that the Hague and Geneva Conventions have
enjoyed a broad accession. Further these fundamental rules are to be observed by all States whether or not they have
ratified the conventions that contain them, because they constitute intransgressible principles of international
customary law.”).
11 Corfu Channel Case (United Kingdom v. Albania), Merits, Judgment, 1949 I.C.J. 4, 22 (“The obligations
incumbent upon the Albanian authorities consisted in notifying, for the benefit of shipping in general, the existence
of a minefield in Albanian territorial waters and in warning the approaching British warships of the imminent danger
to which the minefield exposed them. Such obligations are based, not on the Hague Convention of 1907, No. VIII,
which is applicable in time of war, but on certain general and well-recognized principles, namely: elementary
considerations of humanity, even more exacting in peace than in war; the principle of the freedom of maritime
communication; and every State’s obligation not to allow knowingly its territory to be used for acts contrary to the
rights of other States.”).
12 Refer to § 8.1.4.1 (Common Article 3 of the 1949 Geneva Conventions).
13 Refer to § 8.1.4.2 (Article 75 of AP I and Relevant AP II Provisions).
72
3.2 SITUATIONS TO WHICH THE LAW OF WAR APPLIES
Although the law of war is commonly understood as applying to the conduct of hostilities
and the protection of war victims, the law of war addresses other situations as well. The law of
war establishes:
• rules governing the resort to force (jus ad bellum);14
• rules between enemies for the conduct of hostilities and the protection of war victims in
international and non-international armed conflict;15
• rules between belligerents and neutrals;16
• rules for military occupation;17 and
• duties during peacetime that help implement the above rules.18
In addition, these rules in the law of war can sometimes be applied by analogy to other
contexts.19
3.3 STATUS OF THE PARTIES AND THE LAW OF WAR
The law of war distinguishes between: (1) international armed conflicts, i.e., conflicts
between States; and (2) other armed conflicts, typically called non-international armed conflicts.
Three situations—unrecognized governments, recognition of belligerency, and national
liberation movements—merit further discussion because they may affect whether law of war
rules relating to international armed conflict apply.
3.3.1 International Armed Conflict and Non-International Armed Conflict. The law of
war treats situations of “war,” “hostilities,” or “armed conflict” differently based on the legal
status of parties to the conflict. If two or more States oppose one another, then this type of
armed conflict is known as an “international armed conflict” because it takes place between
States. However, a state of war can exist when States are not on opposite sides of the conflict.20
14 Refer to § 1.11 (Jus ad Bellum).
15 Chapter V addresses the conduct of hostilities.
16 Chapter XV addresses the law of neutrality.
17 Refer to § 11.2 (When Military Occupation Law Applies).
18 Refer to § 3.9 (Law of War Duties Also Applicable in Peace).
19 Refer to § 3.7 (Applying Rules by Analogy).
20 See, e.g., Hamdan v. Rumsfeld, 548 U.S. 557, 630 (2006) (noting that an armed conflict described in Common
Article 3 of the 1949 Geneva Conventions “does not involve a clash between nations.”); The Prize Cases, 67 U.S.
635, 666 (1863) (“it is not necessary to constitute war, that both parties should be acknowledged as independent
nations or sovereign States. A war may exist where one of the belligerents, claims sovereign rights as against the
other.”).
73
These other types of conflict are described as “not of an international character” or “non-
international armed conflict.”21 For example, two non-State armed groups warring against one
another or States warring against non-State armed groups may be described as “non-international
armed conflict,” even if international borders are crossed in the fighting.22
The law of war rules applicable to non-international armed conflict are addressed in
Chapter XVII.23 There are a number of important differences between the law applicable to
international armed conflict and the law applicable to non-international armed conflict.24
3.3.1.1 Application of Jus in Bello Rules Does Not Necessarily Affect the Legal
Status of Parties. Although the legal status of an opponent affects the character of the conflict
and what rules apply as a matter of law, the application of jus in bello rules does not necessarily
affect the legal status of parties to a conflict. For example, a belligerent may, as a policy matter,
afford a person POW protections and treatment without affording that person legal status as a
POW.25 Similarly, the application of humanitarian rules, such as those reflected in Common
Article 3 of the 1949 Geneva Conventions, towards enemy non-State armed groups does not
affect their legal status (e.g., such application does not amount to recognizing the group as lawful
belligerents or as the legitimate government of a State).26
3.3.1.2 Mixed Conflicts Between Opposing States and Non-State Armed Groups.
Rather than viewing a situation as either an international armed conflict or a non-international
armed conflict, it may be possible to characterize parts of a conflict as international in character,
while other parts of that armed conflict may be regarded as non-international in character.27 For
example, under this view, during a situation involving conflict between a variety of States and
non-State armed groups, as between the States, the rules of international armed conflict would
21 See, e.g., Hamdan v. Rumsfeld, 415 F.3d 33, 44 (D.C. Cir. 2005) (Williams, J., concurring) (“Non-state actors
cannot sign an international treaty. Nor is such an actor even a ‘Power’ that would be eligible under Article 2 (P3)
to secure protection by complying with the Convention’s requirements. Common Article 3 fills the gap, providing
some minimal protection for such non-eligibles in an ‘armed conflict not of an international character occurring in
the territory of one of the High Contracting Parties.’ The gap being filled is the non-eligible party’s failure to be a
nation. Thus the words ‘not of an international character’ are sensibly understood to refer to a conflict between a
signatory nation and a non-state actor. The most obvious form of such a conflict is a civil war. But given the
Convention’s structure, the logical reading of ‘international character’ is one that matches the basic derivation of the
word ‘international,’ i.e., between nations. Thus, I think the context compels the view that a conflict between a
signatory and a non-state actor is a conflict ‘not of an international character.’”).
22 Refer to § 17.1.1.2 (NIAC and Internal Armed Conflict).
23 Refer to § 17.1 (Introduction).
24 Refer to § 17.1.3 (Important Differences Between the Law Applicable to International Armed Conflict and the
Law Applicable to Non-International Armed Conflict).
25 Refer to § 9.3.1 (POW Status Versus POW Protections).
26 Refer to § 17.2.3 (Application of Humanitarian Rules and the Legal Status of the Parties to the Conflict).
27 Christopher Greenwood, International Humanitarian Law and the Tadic Case, 7 EUROPEAN JOURNAL OF
INTERNATIONAL LAW 265, 271 (1996) (“[T]here is nothing intrinsically illogical or novel in characterizing some
aspects of a particular set of hostilities as an international armed conflict while others possess an internal character.
Conflicts have been treated as having such a dual aspect where a Government is simultaneously engaged in
hostilities with a rebel movement and with another State which backs that movement.”).
74
apply, while as between the States and non-State armed groups, the rules of non-international
armed conflicts would apply.28
3.3.2 Unrecognized Governments. Even if a State does not recognize an opponent as the
legitimate government of a State, under certain circumstances, rules of international armed
conflict may apply to a conflict between a State and a government that it does not recognize. For
example, members of the regular armed forces who profess allegiance to a government or
authority not recognized by the Detaining Power nonetheless would be entitled to POW status if
they fall into the power of the enemy during international armed conflict.29
3.3.3 State Recognition of Armed Groups as Belligerents. In certain cases, States have
recognized armed groups as belligerents for certain legal purposes.
For the purpose of applying humanitarian rules, recognition of the armed group as having
belligerent rights is neither a prerequisite for nor a result of applying humanitarian rules.30
3.3.3.1 Recognition by Outside States of a Rebel Faction as a Belligerent in a
Civil War. In the past, in cases of a major civil war in a State, other States have recognized the
rebel faction as a belligerent with the effect of treating the rebels as though they were a State
with belligerent rights under the law of neutrality.31
28 See, e.g., Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. United States), Merits,
Judgment, 1986 I.C.J. 14, 114 (¶219) (“The conflict between the contras’ forces and those of the Government of
Nicaragua is an armed conflict which is ‘not of an international character’. The acts of the contras towards the
Nicaraguan Government are therefore governed by the law applicable to conflicts of that character; whereas the
actions of the United States in and against Nicaragua fall under the legal rules relating to international conflicts.
Because the minimum rules applicable to international and to non-international conflicts are identical, there is no
need to address the question whether those actions must be looked at in the context of the rules which operate for the
one or for the other category of conflict.”); Prosecutor v. Thomas Lubanga Dyilo, ICC Trial Chamber I, ICC-01/04-
01/06, Judgment 258 (¶563) (Mar. 14, 2012) (“Similarly, although there is evidence of direct intervention on the
part of Uganda, this intervention would only have internationalised the conflict between the two states concerned
(viz. the DRC and Uganda). Since the conflict to which the UPC/FPLC [Lubanga’s militia] was a party was not ‘a
difference arising between two states’ but rather protracted violence carried out by multiple non-state armed groups,
it remained a non-international conflict notwithstanding any concurrent international armed conflict between
Uganda and the DRC.”).
29 Refer to § 4.5.3 (Regular Armed Forces Who Profess Allegiance to a Government or an Authority Not
Recognized by the Detaining Power).
30 Refer to § 17.2.3 (Application of Humanitarian Rules and the Legal Status of the Parties to the Conflict).
31 For example, STEFAN TALMON, RECOGNITION OF GOVERNMENTS IN INTERNATIONAL LAW 309 (1998) (“Prior to
its installation in Nicaraguan territory the PJNR [Provisional Junta of National Reconstruction] was recognized as
the Government of Nicaragua by the following States: Panama (22 June 1979), Grenada (23 June 1979), Costa Rica
(18 July 1969). In a rare case of recognition of belligerency in modern history, the members of the Andean Group
(Bolivia, Colombia, Ecuador, Peru, and Venezuela) declared on 17 June 1979 that they had recognized both sides in
the Nicaraguan conflict as ‘belligerents’.”); B.F. Butler, Attorney General, Piracy Upon the High Seas, May 17,
1836, 3 OPINIONS OF THE ATTORNEY GENERAL 120, 122 (1852) (“The existence of a civil war between the people of
Texas and the authorities and people of the other Mexican States, was recognised by the President of the United
States at an early day in the month of November last. Official notice of this fact, and of the President’s intention to
preserve the neutrality of the United States, was soon after given to the Mexican government.”); The Santissima
Trinidad, 20 U.S. 283, 337 (1822) (“The government of the United States has recognized the existence of a civil war
between Spain and her colonies, and has avowed a determination to remain neutral between the parties, and to allow
75
Historically, certain conditions had to be satisfied before outside States could recognize a
non-State armed group as a belligerent:
• a general state of armed conflict within a territory;
• the armed group occupies and administers a significant portion of national territory;
• the armed group acts under responsible chain of command and respects the laws of war;
and
• circumstances exist that make it necessary for outside States to define their attitude
toward the conflict.32
This doctrine has not been invoked often, especially after the adoption of the Charter of
the United Nations, and the unwarranted recognition of an insurgent group likely would, at least,
be considered an unfriendly act against a State engaged in hostilities against that group.33
3.3.3.2 Assertion of War Powers by a State Engaged in Hostilities Against a Non-
State Armed Group. Occasionally, a State that has been engaged in hostilities against a non-
State armed group has taken actions that have recognized the belligerency of the non-State armed
group, at least for certain purposes. For example, President Lincoln’s proclamation of a
blockade during the U.S. Civil War was viewed as recognizing the existence of a state of war, at
least for the purposes of imposing the blockade on foreign vessels seeking to trade with the
Confederacy.34
to each the same rights of asylum and hospitality and intercourse. Each party is, therefore, deemed by us a
belligerent nation, having, so far as concerns us, the sovereign rights of war, and entitled to be respected in the
exercise of those rights.”).
32 HERSCH LAUTERPACHT, RECOGNITION IN INTERNATIONAL LAW 175-76 (1947) (“There is general agreement as to
the nature of the conditions which impose the duty of recognition of belligerency—or which, according to others,
justify recognition of belligerency. These conditions are as follows: first, there must exist within the State an armed
conflict of a general (as distinguished from a purely local) character; secondly, the insurgents must occupy and
administer a substantial portion of national territory; thirdly, they must conduct the hostilities in accordance with the
rules of war and through organized armed forces acting under a responsible authority; fourthly, there must exist
circumstances which make it necessary for outside States to define their attitude by means of recognition of
belligerency.”).
33 See, e.g., HERSCH LAUTERPACHT, RECOGNITION IN INTERNATIONAL LAW 239 (1947) (“If a distant continental
State in no way directly concerned with the hostilities at sea were to recognize the insurgents as belligerents, it
would lay itself open to the charge of a gratuitous gesture unfriendly to the lawful government and merely calculated
to encourage the rebellion.”).
34 The Prize Cases, 67 U.S. 635, 670 (1862) (“Whether the President, in fulfilling his duties as Commander-in-chief
in suppressing an insurrection, has met with such armed hostile resistance and a civil war of such alarming
proportions as will compel him to accord to them the character of belligerents is a question to be decided by him,
and this Court must be governed by the decisions and acts of the political department of the Government to which
this power was entrusted. ‘He must determine what degree of force the crisis demands.’ The proclamation of
blockade is itself official and conclusive evidence to the Court that a state of war existed which demanded and
authorized a recourse to such a measure under the circumstances peculiar to the case.”).
76
3.3.3.3 Recognition of Friendly Armed Groups as Lawful Belligerents. In some
cases, a State has recognized an armed group that fights alongside it as a belligerent.35 One
reason for such recognition might be to seek to persuade other States that have not recognized
the armed group as a belligerent, such as an enemy State, to grant the privileges of combatant
status to members of those armed groups.36 An armed group that has been recognized in this
way by a friendly State may be viewed as analogous to an organized resistance movement that
belongs to a State that is a party to a conflict.37
3.3.4 AP I Provision on National Liberation Movements. AP I treats as international
armed conflicts “armed conflicts in which peoples are fighting against colonial domination and
alien occupation and against racist regimes in the exercise of their right of self-determination.”38
The United States has strongly objected to this provision as making the applicability of
the rules of international armed conflict turn on subjective and politicized criteria that would
eliminate the distinction between international and non-international conflicts.39 The United
States has understood these types of conflicts to be non-international armed conflicts.40
35 For example, Case Concerning Certain German Interests in Polish Upper Silesia (Merits) (Germany v. Poland)
P.C.I.J. (series A) No. 7, at 28 (“At the time of the conclusion of those two Conventions, Poland was not recognized
as a belligerent by Germany; it is, however, only on the basis of such recognition that an armistice could have been
concluded between those two Powers. The Principal Allied Powers had, it is true, recognized the Polish armed
forces as an autonomous, allied and co-belligerent (or belligerent) army. This army was placed under the supreme
political authority of the Polish National Committee with headquarters in Paris.”); Statement of the Secretary of
State, September 1918, reprinted in Charles Henry Hyde, The Recognition of the Czecho-Slovaks as Belligerents, 13
AJIL 93-95 (1919) (“The Government of the United States recognizes that a state of belligerency exists between the
Czecho-Slovaks thus organized and the German and Austro-Hungarian Empires. It also recognizes the Czecho-
Slovak National Council as a de facto belligerent government, clothed with proper authority to direct the military
and political affairs of the Czecho-Slovaks.”).
36 For example, Declaration Concerning Czechoslovak Army, Sept. 7, 1944, 11 DEPARTMENT OF STATE BULLETIN
263 (Sept. 10, 1944) (“The United States Government therefore declares: … (3) In these circumstances reprisals by
the German military authorities against the soldiers of the Czechoslovak Army violate the rules of war by which
Germany is bound. The United States Government, therefore, solemnly warns all Germans who take part in or are
in any way responsible for such violations that they do so at their peril and will be held answerable for their
crimes.”).
37 Compare § 4.6.2 (Belonging to a Party to the Conflict).
38 AP I art. 1(4) (“The situations referred to in the preceding paragraph [i.e., the situations referred to in Article 2
common to those Conventions] include armed conflicts in which peoples are fighting against colonial domination
and alien occupation and against racist regimes in the exercise of their right of self-determination, as enshrined in
the Charter of the United Nations and the Declaration on Principles of International Law concerning Friendly
Relations and Co-operation among States in accordance with the Charter of the United Nations.”).
39 See Ronald Reagan, Letter of Transmittal, Jan. 29, 1987, MESSAGE FROM THE PRESIDENT TRANSMITTING AP II III-
IV (“But Protocol I is fundamentally and irreconcilably flawed. It contains provisions that would undermine
humanitarian law and endanger civilians in war. One of its provisions, for example, would automatically treat as an
international conflict any so-called ‘war of national liberation.’ Whether such wars are international or non-
international should turn exclusively on objective reality, not on one’s view of the moral qualities of each conflict.
To rest on such subjective distinctions based on a war’s alleged purposes would politicize humanitarian law and
eliminate the distinction between international and non-international conflicts. It would give special status to ‘wars
of national liberation,’ an ill-defined concept expressed in vague, subjective, politicized terminology.”).
40 Detailed Analysis of Provisions, Attachment 1 to George P. Shultz, Letter of Submittal, Dec. 13, 1986, MESSAGE
FROM THE PRESIDENT TRANSMITTING AP II 1-2 (“This Article technically excludes four types of situations from the
77
Moreover, the United States has not accepted this provision in the context of the CCW.41 The
United States has expressed the view that it would not be appropriate to treat this provision of
AP I as customary international law.42
3.4 WHEN JUS IN BELLO RULES APPLY
Jus in bello treaties often provide that they apply in cases of “declared war or of any
other armed conflict,” even if the state of war is not recognized by them.43 This standard has
also been understood to result in the application of the customary law of war.44
A case of “declared war or any other armed conflict” for the purpose of determining
whether parties must comply with jus in bello rules may be understood as arising in two ways:
(1) when a party intends to conduct hostilities; or (2) when parties are actually conducting
hostilities.
“War,” “hostilities,” and “armed conflict” may be defined differently for other legal
purposes.45 It must be emphasized that the discussion in this section is for the purpose of
assessing whether jus in bello restrictions apply and not necessarily for other purposes. For
example, the fact that jus in bello restrictions apply is not determinative of whether a State’s
actions are lawful under jus ad bellum.46 Similarly, the fact that jus in bello restrictions apply is
scope of the Protocol: … (2) the so-called wars of ‘national liberation’ defined as international armed conflicts by
Article 1(4) of Protocol I Additional to the 1949 Geneva Conventions; … However, the exclusion of the second and
third categories is inappropriate. The second category--so-called ‘liberation wars’ defined in Protocol I--are often in
fact non-international conflicts, and are distinguished by Protocol I from other non-international conflicts only on
the basis of highly politicized and undesirable criteria which detract from the integrity of international humanitarian
law; the United States should therefore reject this distinction.”).
41 Refer to § 19.21.1.2 (U.S. Reservation to Article 7(4)(b) of the CCW).
42 Memorandum submitted in United States v. Shakur, 690 F. Supp. 1291 (S.D.N.Y. 1988), III CUMULATIVE DIGEST
OF UNITED STATES PRACTICE IN INTERNATIONAL LAW 1981-88 3436, 3441 (“The new provisions on wars of
national liberation and prisoners of war in Protocol I clearly do not reflect the practice of states. Indeed, they were
adopted precisely because states did not accord prisoner-of-war status in such conflicts. It is most unlikely that
states will in the future choose to accord prisoner-of-war status in conflicts described as wars of national liberation.
Accordingly, it is the view of the United States that it would be inappropriate to treat these provisions as part of
customary international law under any circumstances.”).
43 See, e.g., GWS art. 2 (The convention applies “to all cases of declared war or of any other armed conflict which
may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by
them.”); GWS-SEA art. 2 (same); GPW art. 2 (same); GC art. 2 (same); 1954 HAGUE CULTURAL PROPERTY
CONVENTION art. 18 (“the present Convention shall apply in the event of declared war or of any other armed conflict
which may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by
one or more of them.”); CCW art. 1 (“This Convention and its annexed Protocols shall apply in the situations
referred to in Article 2 common to the Geneva Conventions of 12 August 1949 for the Protection of War Victims,”).
44 1956 FM 27-10 (Change No. 1 1976) ¶8b (“The customary law of war applies to all cases of declared war or any
other armed conflict which may arise between the United States and other nations, even if the state of war is not
recognized by one of them. The customary law is also applicable to all cases of occupation of foreign territory by
the exercise of armed force, even if the occupation meets with no armed resistance.”).
45 Refer to § 1.5.2 (Different Definitions of “War” for Different Legal Purposes).
46 Refer to § 3.5.2 (Jus in Bello and Jus ad Bellum Generally Operate Independently of One Another).
78
not determinative of whether the permissions that are sometimes viewed as inherent in jus in
bello rules may be relied upon by a State or non-State actor.47
3.4.1 Intent-Based Test for Applying Jus in Bello Rules. Jus in bello rules apply when a
party intends to conduct hostilities.
If a State chooses to go to war, then it is bound by jus in bello rules for the conduct of
those hostilities.48 For example, if a State considers it necessary to respond to attacks with
military force, then those military operations must comply with jus in bello rules.49
The fact that the intention to conduct hostilities gives rise to obligations to comply with
the law of war is important because law of war obligations must be taken into account even
before the fighting actually begins, such as in the planning of military operations.50 Similarly,
certain obligations under the GPW and the GC are triggered by the onset of hostilities, and it
may be necessary to implement these obligations even before the fighting actually begins.51 As
another example, the party that is subject to attack is often in a position to take feasible
precautions for the protection of the civilian population even before the fighting begins.52
3.4.1.1 Declarations of War or Other Official Recognition by States of a State of
Hostilities. The application of the 1949 Geneva Conventions and other law of war treaties to
cases of “declared war” is an example of how jus in bello restrictions apply when a party intends
to conduct hostilities.53 Traditionally, a State could create a state of hostilities with another State
47 Refer to § 1.3.3.2 (Law of War as Permissive Law).
48 L. OPPENHEIM, II INTERNATIONAL LAW 66 (2nd ed., 1912) (“But if [States] choose to go to war they have to
comply with the rules laid down by International Law regarding the conduct of war and the relations between
belligerents and neutral States.”).
49 For example, Patrick F. Philbin, Deputy Assistant Attorney General, Legality of the Use of Military Commissions
to Try Terrorists, Nov. 6, 2001, 25 OPINIONS OF THE OFFICE OF LEGAL COUNSEL 238, 276 (“In addition, the United
States has determined that it is necessary to respond to the attacks with military force. That decision is significant
because one element often cited for determining whether a situation involving a non-state actor rises to the level of
an “armed conflict” (for example, for purposes of common Article 3 of the Geneva Conventions) is whether a state
responds with its regular military forces. The United States has urged this position. See 3 U.S. Practice § 2, at
3443; see also G.I.A.D. Draper, The Red Cross Conventions 15-16 (1958) (under common Article 3, “armed
conflict” exists when the government is “obliged to have recourse to its regular military forces”). Here, this
criterion is overwhelmingly satisfied. As outlined above, the United States has found it necessary to respond with a
massive use of military force. The current operations in Afghanistan and continuing preparations for a sustained
campaign easily establish that the situation here involves an armed conflict for purposes of international law.”).
50 Refer to § 18.8 (Considering Law of War Obligations in the Planning of Military Operations).
51 Refer to § 9.4 (National-Level GPW Implementation Measures); § 10.2 (National-Level GC Implementation
Measures).
52 Refer to § 5.14 (Feasible Precautions to Reduce the Risk of Harm to Protected Persons and Objects by the Party
Subject to Attack).
53 See, e.g., GWS art. 2 (The convention applies “to all cases of declared war … between two or more of the High
Contracting Parties”); GWS-SEA art. 2 (same); GPW art. 2 (same); GC art. 2 (same); 1954 HAGUE CULTURAL
PROPERTY CONVENTION art. 18 (“the present Convention shall apply in the event of declared war … between two or
more of the High Contracting Parties”); CCW art. 1 (“This Convention and its annexed Protocols shall apply in the
situations referred to in Article 2 common to the Geneva Conventions of 12 August 1949 for the Protection of War
Victims,”).
79
simply by providing objective evidence of its decision to resort to force through formal
declarations that hostilities exist between them.54
Although States generally no longer file formal declarations of war with one another,
officials may make public statements that are like declarations of war in that they provide notice
of a state of hostilities.55 For example, States may make statements that indicate their view that
they are engaged in armed conflict in the context of reporting measures taken in the exercise of
their inherent right of self-defense to the U.N. Security Council.56 Similarly, the authorization
by Congress of the use of military force has been interpreted as triggering the application of
certain parts of the law of war.57
These types of statements concerning jus ad bellum may be probative of the applicability
of jus in bello restrictions. For example, a statement by a State indicating that it had suffered a
wrongful attack under jus ad bellum would also indicate that the State viewed jus in bello
restrictions as applicable to its adversary’s operations against it and its own military operations
against its adversary.58
Similarly, statements by States that justify the legality of their actions or assert authority
under jus in bello rules may also provide evidence that States have the intention of conducting
54 See, e.g., Convention (III) Relative to the Opening of Hostilities, art. 1, Oct. 18, 1907, 36 STAT. 2259, 2271 (“The
Contracting Powers recognize that hostilities between themselves must not commence without previous and explicit
warning, in the form either of a reasoned declaration of war or of an ultimatum with conditional declaration of
war.”); Eliza Ann and others, 1 DODSON 244, 247 (Mar. 9, 1813) (a declaration of war “proves the existence of
actual hostilities on one side at least, and puts the other party also into a state of war, though he may, perhaps, think
proper to act on the defensive only.”).
55 See, e.g., Navios Corp. v. The Ulysses II, 161 F. Supp. 932, 943 (D. Md. 1958) (concluding that a speech by
President Nasser of Egypt “of November 1, confirmed by the statement of November 3, constituted a declaration of
war even under the technical requirements of international law.”), affirmed, 260 F.2d 959 (4th Cir. 1958).
56 Refer to § 1.11.5.6 (Reporting to the U.N. Security Council).
57 Talbot v. Seeman, 5 U.S. 1, 28 (1801) (Marshall, C.J.) (“It is not denied, nor in the course of the argument has it
been denied, that congress may authorize general hostilities, in which case the general laws of war apply to our
situation; or partial hostilities, in which case the laws of war, so far as they actually apply to our situation, must be
noticed.”).
58 For example, John O. Brennan, Assistant to the President for Homeland Security and Counterterrorism, Remarks
at Harvard Law School: Strengthening Our Security by Adhering to Our Values and Laws, Sept. 16, 2011 (“First,
our definition of the conflict. As the President has said many times, we are at war with al-Qa’ida. In an indisputable
act of aggression, al-Qa’ida attacked our nation and killed nearly 3,000 innocent people. And as we were reminded
just last weekend, al-Qa’ida seeks to attack us again. Our ongoing armed conflict with al-Qa’ida stems from our
right—recognized under international law—to self defense. An area in which there is some disagreement is the
geographic scope of the conflict. The United States does not view our authority to use military force against al-
Qa’ida as being restricted solely to ‘hot’ battlefields like Afghanistan. Because we are engaged in an armed conflict
with al-Qa’ida, the United States takes the legal position that —in accordance with international law—we have the
authority to take action against al-Qa’ida and its associated forces without doing a separate self-defense analysis
each time. And as President Obama has stated on numerous occasions, we reserve the right to take unilateral action
if or when other governments are unwilling or unable to take the necessary actions themselves. That does not mean
we can use military force whenever we want, wherever we want. International legal principles, including respect for
a state’s sovereignty and the laws of war, impose important constraints on our ability to act unilaterally—and on the
way in which we can use force—in foreign territories.”).
80
hostilities and that jus in bello restrictions apply to the activities that will effectuate those
intentions.59
3.4.1.2 Non-State Armed Groups With the Intention of Conducting Hostilities. A
non-State armed group, such as a rebel group, might also intend to conduct hostilities.60 Non-
State armed groups are similarly bound by the restrictions in the law of war for the conduct of
hostilities when they intend to conduct hostilities.61 However, in contrast to States, non-State
armed groups lack competent authority.62 Thus, there would not be a basis for non-State armed
groups to claim the permissions that may be viewed as inherent in parts of the law of war.63 For
example, members of a non-State group may be subject to prosecution under a State’s domestic
law for their participation in hostilities against it.64
3.4.2 Act-Based Test for Applying Jus in Bello Rules. Jus in bello rules apply when
parties are actually conducting hostilities, even if the war is not declared or if the state of war is
59 Legal and Practical Consequences of a Blockade of Cuba, Oct. 19, 1962, 1 SUPPLEMENTAL OPINIONS OF THE
OFFICE OF LEGAL COUNSEL 486, 488-89 (2013) (“The declaration of a state of war was helpful in ascertaining the
rights and obligations of neutrals in a given situation. Apart from this, however, it served little function. War itself,
whatever its reason, was legal self-help, and so were lesser measures if such could be said to exist. Whether or not a
nation declared a state of war it would be found by others to exist if that state were claiming rights, such as
blockade, normally associated with war.”). For example, National Defense Authorization Act for Fiscal Year 2012
§ 1021 (“Congress affirms that the authority of the President to use all necessary and appropriate force pursuant to
the Authorization for Use of Military Force (Public Law 107-40; 50 U.S.C. 1541 note) includes the authority for the
Armed Forces of the United States to detain covered persons (as defined in subsection (b)) pending disposition
under the law of war.”); Hugh J. Clausen & W. Hays Parks, Geneva Conventions Status of Enemy Personnel
Captured During URGENT FURY, DAJA-IA 1983/7031 (Nov. 4, 1983), III CUMULATIVE DIGEST OF UNITED
STATES PRACTICE IN INTERNATIONAL LAW 1981-1988 3452, 3454 (considering, inter alia, the fact that “[t]he
Department of State, in a press release on 4 November 9 [1984], cited the GPW as authority for U.S. detention of
Cuban Grenadan military personnel” in concluding that “de facto hostilities existed on Grenada and that the Geneva
Conventions do apply.”) (insertion reflect in the Digest).
60 For example, Hamdan v. Rumsfeld, 548 U.S. 557, 687 (2006) (Thomas, J., dissenting) (“According to the State
Department, al Qaeda declared war on the United States as early as August 1996. In February 1998, al Qaeda
leadership issued another statement ordering the indiscriminate—and, even under the laws of war as applied to
legitimate nation-states, plainly illegal—killing of American civilians and military personnel alike. This was not
mere rhetoric; even before September 11, 2001, al Qaeda was involved in the bombing of the World Trade Center in
New York City in 1993, the bombing of the Khobar Towers in Saudi Arabia in 1996, the bombing of the U. S.
Embassies in Kenya and Tanzania in 1998, and the attack on the U. S. S. Cole in Yemen in 2000.”) (internal
citations omitted). See also United States v. Burr, 25 F. Cas. 201, 203 (C.C.D. Va. 1807) (Marshall, C.J.)
(explaining in the context of a prosecution of rebels for treason that “war might be levied without a battle, or the
actual application of force to the object on which it was designed to act; that a body of men assembled for the
purpose of war, and being in a posture of war, do levy war; and from that opinion I have certainly felt no disposition
to recede. But the intention is an indispensable ingredient in the composition of the fact; and if war may be levied
without striking the blow, the intention to strike must be plainly proved.”).
61 Refer to § 17.2.4 (Binding Force of the Law of War on Insurgents and Other Non-State Armed Groups).
62 Refer to § 1.11.1.1 (Competent Authority (Right Authority) to Wage War for a Public Purpose).
63 Refer to § 1.3.3.2 (Law of War as Permissive Law).
64 Refer to § 17.4.1 (Ability of a State to Use Its Domestic Law Against Non-State Armed Groups).
81
not recognized by them.65 The de facto existence of an armed conflict is sufficient to trigger
obligations for the conduct of hostilities.66
The United States has interpreted “armed conflict” in Common Article 2 of the 1949
Geneva Conventions to include “any situation in which there is hostile action between the armed
forces of two parties, regardless of the duration, intensity or scope of the fighting.”67
3.4.2.1 Reasons for States to Seek to Deny the Existence of Hostilities. States
have specified that jus in bello rules apply even if a state of hostilities is not recognized by them
because States have frequently denied that they are at “war.” And, in some cases, this denial has
resulted in a refusal to comply with jus in bello obligations.68
65 See, e.g., GWS art. 2 (The convention applies “to all cases of declared war or of any other armed conflict which
may arise between two or more of the High Contracting Parties, even if the state of war is not recognized by them.”)
(emphasis added); GWS-SEA art. 2 (same); GPW art. 2 (same); GC art. 2 (same); 1954 HAGUE CULTURAL
PROPERTY CONVENTION art. 18 (“the present Convention shall apply in the event of declared war or of any other
armed conflict which may arise between two or more of the High Contracting Parties, even if the state of war is not
recognized by one or more of them.”) (emphasis added); CCW art. 1 (“This Convention and its annexed Protocols
shall apply in the situations referred to in Article 2 common to the Geneva Conventions of 12 August 1949 for the
Protection of War Victims,”).
66 GPW COMMENTARY 22-23 (“There is no need for a formal declaration of war, or for the recognition of the
existence of a state of war, as preliminaries to the application of the Convention. The occurrence of de facto
hostilities is sufficient.”). For example, Hugh J. Clausen & W. Hays Parks, Geneva Conventions Status of Enemy
Personnel Captured During URGENT FURY, DAJA-IA 1983/7031 (Nov. 4, 1983), III CUMULATIVE DIGEST OF
UNITED STATES PRACTICE IN INTERNATIONAL LAW 1981-1988 3452, 3454 (concluding “that de facto hostilities
existed on Grenada and that the Geneva Conventions do apply” despite the fact that “[n]o party to the hostilities in
Grenada has suggested that a state of war exists; officials of Cuba and the United States publicly have announced
they are not at war.”); George Aldrich, Assistant Legal Adviser for Far Eastern Affairs, Department of State,
Entitlement of American Military Personnel Held by North Viet-Nam to Treatment as Prisoners of War Under the
Geneva Convention of 1949 Relative to the Treatment of Prisoners of War, Jul. 13, 1966, X WHITEMAN’S DIGEST
231-32 (§7) (“Although there have been no declarations of war, the present conflict in Vietnam is indisputably an
‘armed conflict’ between parties to the Geneva Conventions of 1949. In one aspect of the war, American aircraft are
operating against military targets in North Vietnam, and North Vietnamese forces have engaged these aircraft.
Under these circumstances, the Convention applies in its entirety to this conflict. … In this case, the state of war
(under international law) is not disputed; it is merely undeclared.”).
67 Department of State, Telegram 348126 to American Embassy at Damascus, Dec. 8, 1983, III CUMULATIVE
DIGEST OF UNITED STATES PRACTICE IN INTERNATIONAL LAW 1981-1988 3456, 3457 (“The Third Geneva
Convention accords ‘prisoner-of-war’ status to members of the armed forces who are captured during ‘armed
conflict’ between two or more parties to the Convention. ‘Armed conflict’ includes any situation in which there is
hostile action between the armed forces of two parties, regardless of the duration, intensity or scope of the fighting
and irrespective of whether a state of war exists between the two parties.”). Cf. Bas v. Tingy, 4 U.S. 37, 40 (1800)
(Washington, J., concurring) (“every contention by force between two nations, in external matters, under the
authority of their respective governments, is not only war, but public war.”).
68 For example, United States, et al. v. Araki, et al., Majority Judgment, International Military Tribunal for the Far
East, 49,602, reprinted in NEIL BOISTER & ROBERT CRYER, DOCUMENTS ON THE TOKYO INTERNATIONAL MILITARY
TRIBUNAL: CHARTER, INDICTMENT AND JUDGMENTS 535 (2008) (“Since the Government of Japan officially
classified the China War as an ‘Incident’ and considered Chinese soldiers in Manchuria as ‘bandits’ the Army
refused to accord to captives taken in the fighting the status and the rights of prisoners of war. MUTO says that it
was officially decided in 1938 to continue to call the war in China an ‘Incident’ and to continue for that reason to
refuse to apply the rules of war to the conflict. TOJO told us the same.”).
82
There are a variety of reasons why States might deny that they are at “war.” For
example, government officials may deny that an armed conflict exists: (1) to avoid an escalation
in fighting and to facilitate a diplomatic resolution; (2) for reasons of domestic law; (3) to avoid
economic costs (such as discouraging commerce and foreign investment); or (4) to avoid
appearing to acknowledge the military effectiveness of an opposing force.
In particular, States have often been reluctant to acknowledge that operations by non-
State armed groups have triggered the application of Common Article 3 of the 1949 Geneva
Conventions.69 This reluctance often stems from an unwillingness to take any action that could
enhance the perceived status of rebels or give any appearance of legitimacy to their actions.70
Nonetheless, the application of the humanitarian rules does not affect the legal status of parties to
a conflict.71
3.4.2.2 Distinguishing Armed Conflict From Internal Disturbances and Tensions.
In assessing whether de facto hostilities exist for the purpose of applying jus in bello restrictions,
situations of internal disturbances and tensions, such as riots, isolated and sporadic acts of
violence, and other acts of a similar nature do not amount to armed conflict.72
69 See, e.g., George H. Aldrich, Deputy Legal Adviser, Department of State, Human Rights in Armed Conflict:
Development of the Law, Apr. 13, 1973, 68 DEPARTMENT OF STATE BULLETIN, 876, 878 (Jun. 18, 1973) (“I would
note that Pakistan in Bangladesh and the United Kingdom in Northern Ireland have refused to acknowledge the
applicability of article 3 common to the four Geneva Conventions concerning noninternational armed conflicts.”).
70 See, e.g., George H. Aldrich, Deputy Legal Adviser, Department of State, Human Rights in Armed Conflict:
Development of the Law, Apr. 13, 1973, 68 DEPARTMENT OF STATE BULLETIN, 876, 879 (Jun. 18, 1973) (“In the
first place there is a general concern of governments that the acceptance of international standards for a civil war
connotes international recognition of the insurgents. This concern results from the historical development of the
law; in customary law the international laws of war become applicable to a civil war upon international recognition
of the rebels as belligerents. This concern persists despite an explicit provision in common article 3 that its
application shall not affect the legal status of the parties to the conflict. Personally, I deplore the fact that this
concern so often effectively prevents official admission that an internal armed conflict is one to which article 3
applies, but we cannot ignore that political reality. Governments will predictably remain unwilling to do anything
that could enhance the perceived status of rebels or give any appearance of legitimacy to their actions.”).
71 Refer to § 17.2.3 (Application of Humanitarian Rules and the Legal Status of the Parties to the Conflict).
72 See, e.g., CCW AMENDED art. 1 (2) (“This Convention and its annexed Protocols shall not apply to situations of
internal disturbances and tensions, such as riots, isolated and sporadic acts of violence, and other acts of similar
nature, as not being armed conflicts.”); CCW AMENDED MINES PROTOCOL art. 1(2) (“This Protocol shall not apply
to situations of internal disturbances and tensions, such as riots, isolated and sporadic acts of violence and other acts
of a similar nature, as not being armed conflicts.”); United States, Statement on Ratification of the International
Convention for the Suppression of the Financing of Terrorism, Jun. 26, 2002, 2185 UNTS 611, 612 (“(2) Meaning
of the term armed conflict. The United States of America understands that the term ‘armed conflict’ in Article 2 (1)
(b) of the Convention does not include internal disturbances and tensions, such as riots, isolated and sporadic acts of
violence, and other acts of a similar nature.”). Consider AP II art. 1(2) (“This Protocol shall not apply to situations
of internal disturbances and tensions, such as riots, isolated and sporadic acts of violence and other acts of a similar
nature, as not being armed conflicts.”); ROME STATUTE art. 8(2)(d) (“Paragraph 2(c) applies to armed conflicts not
of an international character and thus does not apply to situations of internal disturbances and tensions, such as riots,
isolated and sporadic acts of violence or other acts of a similar nature.”); ROME STATUTE art. 8(2)(f) (“Paragraph
2(e) applies to armed conflicts not of an international character and thus does not apply to situations of internal
disturbances and tensions, such as riots, isolated and sporadic acts of violence or other acts of a similar nature.”).
83
Any hostile action between the armed forces of different States (i.e., international armed
conflict) may readily be distinguished from an “internal disturbance or tension.” However, it has
been more difficult to distinguish “armed conflict not of an international character” from
“internal disturbances or tensions.”
“Armed conflict not of an international character” for the purpose of applying the
obligations in Common Article 3 of the 1949 Geneva Conventions was not specifically defined
in those conventions.73 There has been a range of views on what constitutes an “armed conflict
not of an international character” for this purpose.74 The intensity of the conflict and the
organization of the parties are criteria that have been assessed to distinguish between non-
international armed conflict and “internal disturbances and tensions.”75 A variety of factors have
been considered in assessing these criteria and in seeking to distinguish between armed conflict
and internal disturbances and tensions.76
73 GWS COMMENTARY 49 (“What is meant by ‘armed conflict not of an international character’? That was the
burning question which arose again and again at the Diplomatic Conference. The expression was so general, so
vague, that many of the delegations feared that it might be taken to cover any act committed by force of arms—any
form of anarchy, rebellion, or even plain banditry. For example, if a handful of individuals were to rise in rebellion
against the State and attack a police station, would that suffice to bring into being an armed conflict within the
meaning of the Article? In order to reply to questions of this sort, it was suggested that the term ‘conflict’ should be
defined or, which would come to the same thing, that a certain number of conditions for the application of the
Convention should be enumerated. The idea was finally abandoned—wisely, we think.”).
74 See, e.g., Prosecutor v. Tadić, ICTY Appeals Chamber, IT-94-1-A, Decision on the Defence Motion for
Interlocutory Appeal on Jurisdiction, ¶70 (Oct. 2, 1995) (“On the basis of the foregoing, we find that an armed
conflict exists whenever there is a resort to armed force between States or protracted armed violence between
governmental authorities and organized armed groups or between such groups within a State.”); Juan Carlos Abella
v. Argentina, Inter-American Commission on Human Rights, Organization of American States, Case 11.137,
OEA/Ser.L/V/II.98, ¶152 (Nov. 18, 1997) (“Common Article 3 is generally understood to apply to low intensity and
open armed confrontations between relatively organized armed forces or groups that take place within the territory
of a particular State.”).
75 See, e.g., Prosecutor v. Tadić, ICTY Trial Chamber, IT-94-1-A, Judgment, ¶562 (May 7, 1997) (“In an armed
conflict of an internal or mixed character, these closely related criteria are used solely for the purpose, as a
minimum, of distinguishing an armed conflict from banditry, unorganized and short-lived insurrections, or terrorist
activities, which are not subject to international humanitarian law.”); Prosecutor v. Akayesu, ICTR Trial Chamber,
ICTR-96-4-T, Judgment, ¶625 (Sept. 2, 1998) (“The concept of armed conflict has already been discussed in the
previous section pertaining to Common Article 3. It suffices to recall that an armed conflict is distinguished from
internal disturbances by the level of intensity of the conflict and the degree of organization of the parties to the
conflict.”).
76 See, e.g., GPW COMMENTARY 35-36 (collecting conditions that States negotiating the 1949 Geneva Conventions
viewed as indicative factors); Prosecutor v. Boskoski, ICTY Trial Chamber II, IT-04-82-T, Judgment, ¶177 (Jul. 10,
2008) (“Various indicative factors have been taken into account by Trial Chambers to assess the ‘intensity’ of the
conflict. These include the seriousness of attacks and whether there has been an increase in armed clashes, the
spread of clashes over territory and over a period of time, any increase in the number of government forces and
mobilisation and the distribution of weapons among both parties to the conflict, as well as whether the conflict has
attracted the attention of the United Nations Security Council, and whether any resolutions on the matter have been
passed. Trial Chambers have also taken into account in this respect the number of civilians forced to flee from the
combat zones; the type of weapons used, in particular the use of heavy weapons, and other military equipment, such
as tanks and other heavy vehicles; the blocking or besieging of towns and the heavy shelling of these towns; the
extent of destruction and the number of casualties caused by shelling or fighting; the quantity of troops and units
deployed; existence and change of front lines between the parties; the occupation of territory, and towns and
villages; the deployment of government forces to the crisis area; the closure of roads; cease fire orders and
84
A helpful rule of thumb may be that where parties are, in fact, engaged in activities that
the law of war contemplates (e.g., detention of enemy military personnel without criminal
charge, bombardment of military objectives), those activities are subject to the law of war.77
3.4.2.3 Responding to Ordinary Crimes, Including Acts of Terrorism. States are
not required to apply law of war rules when using domestic law enforcement tools to respond to
ordinary crimes, including acts of terrorism.78 For example, States may apply their domestic law
and prosecute acts of terrorism by non-State armed groups.79 States, however, have at times
decided to resort to military force to counter a terrorist or similar threat that is beyond the
capabilities of ordinary law enforcement to address.80 If States intend to conduct hostilities, then
agreements, and the attempt of representatives from international organisations to broker and enforce cease fire
agreements.”); Prosecutor v. Dordevic, ICTY Trial Chamber II, IT-04-82-T, Judgment, ¶1526 (Feb. 23, 2011)
(“Trial Chambers have taken into account a number of factors when assessing the organization of an armed group.
These fall into five broad groups. First, are the factors signalling the presence of a command structure. Secondly,
are factors indicating that an armed group could carry out operations in an organised manner. Thirdly, are factors
indicating a level of logistics have been taken into account. Fourthly, are factors relevant to determining whether an
armed group possessed a level of discipline and the ability to implement the basic obligations of Common Article 3.
A fifth group includes factors indicating that the armed group was able to speak with one voice.”).
77 Juan Carlos Abella v. Argentina, Inter-American Commission on Human Rights, Organization of American
States, Case 11.137, OEA/Ser.L/V/II.98, ¶155 (Nov. 18, 1997) (“What differentiates the events at the La Tablada
base from these situations [of internal disturbances] are the concerted nature of the hostile acts undertaken by the
attackers, the direct involvement of governmental armed forces, and the nature and level of the violence attending
the events in question. More particularly, the attackers involved carefully planned, coordinated and executed an
armed attack, i.e., a military operation, against a quintessential military objective - a military base.”); GPW
COMMENTARY 23 (“It makes no difference how long the conflict lasts, how much slaughter takes place, or how
numerous are the participating forces; it suffices for the armed forces of one Power to have captured adversaries
falling within the scope of Article 4. Even if there has been no fighting, the fact that persons covered by the
Convention are detained is sufficient for its application. The number of persons captured in such circumstances is,
of course, immaterial.”).
78 United Kingdom, Statement on Ratification of AP I, Jan. 28, 1998, 2020 UNTS 75, 76 (“It is the understanding of
the United Kingdom that the term ‘armed conflict’ of itself and in its context denotes a situation of a kind which is
not constituted by the commission of ordinary crimes including acts of terrorism whether concerted or in
isolation.”).
79 Refer to § 17.4.1 (Ability of a State to Use Its Domestic Law Against Non-State Armed Groups).
80 For example, William J. Clinton, Address to the Nation on Military Action Against Terrorist Sites in Afghanistan
and Sudan, Aug. 20, 1998, 1998-II PUBLIC PAPERS OF THE PRESIDENTS 1460, 1461 (“America has battled terrorism
for many years. Where possible, we’ve used law enforcement and diplomatic tools to wage the fight. … But there
have been and will be times when law enforcement and diplomatic tools are simply not enough, when our very
national security is challenged, and when we must take extraordinary steps to protect the safety of our citizens. With
compelling evidence that the bin Ladin network of terrorist groups was planning to mount further attacks against
Americans and other freedom-loving people, I decided America must act. And so this morning, based on the
unanimous recommendation of my national security team, I ordered our armed forces to take action to counter an
immediate threat from the bin Ladin network. Earlier today, the United States carried out simultaneous strikes
against terrorist facilities and infrastructure in Afghanistan.”); Public Committee against Torture in Israel, et al. v.
Government of Israel, et al., HCJ 769/02, Israel Supreme Court Sitting as the High Court of Justice, ¶21 (Dec. 11,
2005) (“Indeed, in today’s reality, a terrorist organization is likely to have considerable military capabilities. At
times they have military capabilities that exceed those of states. Confrontation with those dangers cannot be
restricted within the state and its penal law.”).
85
they are also bound by the applicable jus in bello restrictions in the law of war.81
Acts of terrorism during armed conflict are prohibited by the law of war.82
3.5 RELATIONSHIP BETWEEN JUS IN BELLO AND JUS AD BELLUM
3.5.1 General Distinction Between Jus in Bello and Jus ad Bellum. As a general matter,
jus in bello and jus ad bellum address different legal issues and should not be conflated.83
Conflating jus in bello and jus ad bellum risks misunderstanding and misapplying these
concepts. For example, in jus ad bellum, proportionality refers to the principle that the overall
goal of the State in resorting to war should not be outweighed by the harm that the war is
expected to produce.84 However, proportionality in jus in bello generally refers to the standard
that the expected incidental harm to the civilian population and civilian objects should not be
disproportionate to the anticipated military advantage from an attack.85 Therefore, although a jus
ad bellum proportionality analysis might consider the harm suffered by enemy military forces in
the fighting, a jus in bello proportionality analysis would not.
3.5.2 Jus in Bello and Jus ad Bellum Generally Operate Independently of One Another.
One important attribute of rules for conduct during war (jus in bello) is that, in general, they
operate independently from rules regarding the resort to force (jus ad bellum).
3.5.2.1 Compliance With Jus in Bello Is Required Regardless of Compliance With
Jus ad Bellum. States fighting against one another must adhere to rules relating to the conduct of
hostilities (jus in bello), regardless of whether a State may be considered the aggressor or
whether the initial resort to force was lawful under jus ad bellum. For example, the 1949 Geneva
Conventions require States to undertake to respect and to ensure respect for the conventions in
all circumstances.86 The phrase “in all circumstances” has been interpreted to mean that a
Party’s obligations to respect and to ensure respect for the 1949 Geneva Conventions applies
regardless of whether a Party to the Convention is the aggressor or lawfully using force in self-
defense.87 Similarly, once an occupation exists in fact, the law of occupation applies, regardless
of whether the invasion was lawful under jus ad bellum.88
81 Refer to § 3.4.1 (Intent-Based Test for Applying Jus in Bello Rules).
82 Refer to § 10.5.3.2 (Collective Penalties and Measures of Intimidation or Terrorism); § 17.6.5 (Prohibition on
Acts of Terrorism).
83 Refer to § 1.11 (Jus ad Bellum).
84 Refer to § 1.11.1.2 (The Means Must Be Proportionate to the Just Cause (Proportionality - Jus ad Bellum)).
85 Refer to § 5.12 (Proportionality in Conducting Attacks).
86 GWS art. 1 (“The High Contracting Parties undertake to respect and to ensure respect for the present Convention
in all circumstances.”).
87 GWS COMMENTARY 27 (“The words ‘in all circumstances’ mean in short that the application of the Convention
does not depend on the character of the conflict. Whether a war is ‘just’ or ‘unjust’, whether it is a war of
aggression or of resistance to aggression, the protection and care due to the wounded and sick are in no way
affected.”). Consider AP I preamble (“the provisions of the Geneva Conventions of 12 August 1949 and of this
Protocol must be fully applied in all circumstances to all persons who are protected by those instruments, without
86
3.5.2.2 Compliance With Jus ad Bellum Is Required Regardless of Compliance
With Jus in Bello. Compliance with jus ad bellum is required regardless of compliance with jus
in bello.89 For example, a State that complies with jus in bello rules may nonetheless commit
aggression under jus ad bellum.90 In addition, violations of law of war treaties applicable to non-
international armed conflict generally have not been understood to provide a basis in
international law for a non-belligerent State to intervene against the State in that conflict.91
3.5.2.3 Rationales for the Independent Operation of Jus in Bello and Jus ad
Bellum. The principle that jus in bello rules operate independently of jus ad bellum rules is
based on principles of sovereignty and humanity, as well as practical considerations.
If the law of war only protected parties justly resorting to force, then both sides, believing
their opponent’s cause to be unjust, could consider themselves free to depart from jus in bello
rules.92 As a consequence, both sides could deny protections to their opponent, and no one
would benefit from the law of war’s humanitarian protections.93 Moreover, there might not be a
competent procedure for deciding which, if any, State has unlawfully resorted to force.94
any adverse distinction based on the nature or origin of the armed conflict or on the causes espoused by or attributed
to the Parties to the conflict,”).
88 Refer to § 11.2.1 (Military Occupation as a Fact).
89 Consider AP I preamble (“nothing in this Protocol or in the Geneva Conventions of 12 August 1949 can be
construed as legitimizing or authorizing any act of aggression or any other use of force inconsistent with the Charter
of the United Nations,”).
90 Refer to § 1.11.3.1 (Aggression).
91 Refer to § 17.18.1 (Duty of Non-Belligerent States to Refrain From Supporting Hostilities by Non-State Armed
Groups Against Other States).
92 VATTEL, THE LAW OF NATIONS 305 (3.12.190) (“Moreover, since each Nation claims to have justice on its side, it
will arrogate to itself all the rights of war and claim that its enemy has none, that his hostilities are but deeds of
robbery, acts in violation of the Law of Nations, and deserving of punishment by all Nations. The decision of the
rights at issue will not be advanced thereby, and the context will become more cruel, more disastrous in its effects,
and more difficult of termination.”).
93 VATTEL, THE LAW OF NATIONS 305 (3.12.190) (“The first rule of that law [of nations], with respect to the subject
under consideration, is that regular war, as regards its effects, must be accounted just on both sides. This principle,
as we have just shown, is absolutely necessary if any law or order is to be introduced into a method of redress as
violent as that of war, if any bounds are to be set to the disasters it occasions, and if a door is to be left at all times
open for the return of peace. Moreover, any other rule would be impractical as between Nation and Nation, since
they recognize no common judge.”).
94 LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW 218 (§61) (“Unless war is to degenerate into a savage
contest of physical forces freed from all restraints of compassion, chivalry and respect for human life and dignity, it
is essential that the accepted rules of war should continue to be observed. This is so in particular in view of the fact
that in the present state of international judicial and political organisation there may be no means by which an
authoritative judgment can be arrived at on the question as to which State is the aggressor. (It will be noted, for
instance, that nothing short of an unanimous vote of the permanent members of the Security Council is sufficient for
the determination that a particular State has resorted to war in violation of its obligations under the Charter.)
Accordingly it must be held that during the war all belligerents are bound to respect and are entitled to insist as
among themselves on the observance of rules of war as generally recognised.”).
87
The principle that jus in bello rules operate independently of jus ad bellum rules is also
influenced by the fact that it would be unjust to punish individual military members based on jus
ad bellum considerations when they have no influence on whether their State has resorted to
force lawfully under applicable international law.95
3.5.3 Jus in Bello and Jus ad Bellum Are Sometimes Related. Although as a general
matter parties must comport with jus in bello rules, regardless of jus ad bellum considerations,
sometimes jus ad bellum issues can affect how jus in bello rules operate.
For example, the jus ad bellum principle of competent authority (also called right
authority) acknowledges that the resort to military force is a prerogative of the State.96
Competent authority is reflected in the distinction between international armed conflict and non-
international armed conflict; military operations against another State are fundamentally different
as a matter of law than military operations against a non-State armed group.97 Competent
authority also is reflected in jus in bello rules relating to who is entitled to receive the privileges
of combatant status. Private persons captured after engaging in hostilities generally are not
entitled to receive the privileges of POW status under the law of war because they lack
competent authority.98
As another example, the jus ad bellum issue of whether a disputed territory belongs to a
State affects whether the law of belligerent occupation applies to that territory because the law of
belligerent occupation only applies to territory that belongs to an enemy State.99
3.5.4 U.N. Security Council Decisions and Jus in Bello. The Charter of the United
Nations provides the modern treaty framework for jus ad bellum, and assigns important
responsibilities to the U.N. Security Council.100
In theory, decisions by the Security Council, acting under Chapter VII of the Charter of
the United Nations, could create obligations that conflict with, and prevail over, obligations in
law of war treaties or customary international law.101 In practice, however, the U.N. Security
Council frequently has affirmed the obligations of States and parties to conflicts to comply with
95 United States v. Josef Altstoetter, et al. (Justice Case), III TRIALS OF WAR CRIMINALS BEFORE THE NMT 1027 (“If
we should adopt the view that by reason of the fact that the war was a criminal war of aggression every act which
would have been legal in a defensive war was illegal in this one, we would be forced to the conclusion that every
soldier who marched under orders into occupied territory or who fought in the homeland was a criminal and a
murderer. The rules of land warfare upon which the prosecution has relied would not be the measure of conduct and
the pronouncement of guilt in any case would become a mere formality.”).
96 Refer to § 1.11.1.1 (Competent Authority (Right Authority) to Wage War for a Public Purpose).
97 Refer to § 3.3.1 (International Armed Conflict and Non-International Armed Conflict).
98 Refer to § 4.18.3 (Private Persons Who Engage in Hostilities - Lack of the Privileges of Combatant Status).
99 Refer to § 11.2.2.3 (“Of the Hostile Army” - Belligerent Occupation Applies to Enemy Territory).
100 Refer to § 1.11.2 (U.N. Charter Framework and the U.N. Security Council).
101 Refer to § 1.11.2.1 (U.N. Member State Obligations With Respect to U.N. Security Council Decisions).
88
the law of war, including military forces operating pursuant to U.N. Security Council
decisions.102
The U.N. Security Council also has certain authorities to respond to situations involving
violations of the law of war, including establishing commissions of inquiry or authorizing the use
of force.103
Decisions of the Security Council, however, may alter the obligations of member States
of the United Nations under the law of neutrality.104 In addition, a U.N. Security Council
authorization may provide additional authority for an Occupying Power to govern occupied
territory.105
3.6 RECIPROCITY AND LAW OF WAR RULES
“Reciprocity” sometimes refers to the idea that whether a law of war rule applies to a
party to a conflict depends on whether its opponent has accepted and complies with that same
rule or a corresponding rule. The requirement to comply with many law of war rules (such as the
obligation to treat detainees humanely) does not depend on whether the enemy complies with
that rule. Nonetheless, in the law of war, reciprocity may play a role in: (1) whether a rule
applies; (2) enforcing a rule; or (3) how a rule operates.
3.6.1 Treaty Provisions That Provide for Reciprocity in the Scope of Application of the
Treaty. Considerations of reciprocity - i.e., the degree of confidence as to whether an adversary
will, in fact, abide by a certain rule - may be a critical factor in the willingness of States to enter
into treaty obligations.
Similarly, various treaty provisions also reflect, to varying degrees, the principle that
whether a rule is legally binding on a party depends on whether its opponent has accepted and
applied that same rule. For example, some law of war treaties have a “general participation
clause” - i.e., a clause specifying that the treaty only applies to an armed conflict if all the parties
to the armed conflict are also Parties to the treaty.106 A number of treaties on the law of
102 For example, U.N. SECURITY COUNCIL RESOLUTION 2011(2011), U.N. Doc. S/RES/2011 (2011) (Oct. 12, 2011)
(“Expressing its serious concern with the increased high number of civilian casualties in Afghanistan, in particular
women and children casualties, the increasingly large majority of which are caused by Taliban, Al-Qaida and other
violent and extremist groups, reaffirming that all parties to armed conflict must take all feasible steps to ensure the
protection of affected civilians, especially women, children and displaced persons, calling for all parties to comply
with their obligations under international humanitarian and human rights law and for all appropriate measures to be
taken to ensure the protection of civilians, and recognizing the importance of the ongoing monitoring and reporting
to the United Nations Security Council, including by ISAF, of the situation of civilians and in particular civilian
casualties, and noting in this regard the work of the ISAF Civilian Casualties Tracking Cell,”).
103 Refer to § 18.12 (U.N. Security Council and Enforcement of the Law of War).
104 Refer to § 15.2.3 (The Law of Neutrality Under the Charter of the United Nations).
105 Refer to § 11.1.2.5 (Occupation and U.N. Security Council Resolutions).
106 For example, HAGUE IV art. 2 (“The provisions contained in the Regulations referred to in Article 1, as well as in
the present Convention, do not apply except between Contracting Powers, and then only if all the belligerents are
parties to the Convention.”); HAGUE V art. 20 (“The provisions of the present Convention do not apply except
between Contracting Powers, and then only if all the belligerents are parties to the Convention.”); HAGUE IX art. 8
89
neutrality have such a clause.107 Other treaties specify that if both Parties and non-Parties to a
treaty are in an armed conflict, then Parties to the treaty remain bound by the treaty in their
mutual relations, but not in relation to States that are not Parties to the treaty.108 Treaties have
also provided that if a State in an armed conflict is not a Party to the treaty, but it accepts and
applies the treaty’s provisions, then the Parties to the treaty are bound by the treaty in relation to
that State.109
These provisions, however, only determine the application of the treaty as matter of
treaty law and not as customary international law. For example, although not all parties to World
War II were Parties to Hague IV (thus failing to satisfy the requirements of Hague IV’s general
participation clause), Hague IV’s humanitarian protections were deemed applicable as a matter
of customary international law.110
3.6.2 Reciprocity in the Enforcement of the Law of War. Reciprocity may be reflected in
the enforcement of the law of war. For example, the principle of reciprocity is reflected in the
concept of reprisal, which under very limited circumstances permits a belligerent to take action
that would otherwise be unlawful in order to remedy an enemy’s breach of the law.111 However,
the prohibitions on reprisal in the law of war also may be understood to reflect important
limitations on the principle of reciprocity in enforcing the law of war.112
(“The provisions of the present Convention do not apply except between Contracting Powers, and then only if all the
belligerents are parties to the Convention.”); HAGUE XIII art. 28 (“The provisions of the present Convention do not
apply except to the Contracting Powers, and then only if all the belligerents are parties to the Convention.”); 1929
GPW art. 82 (“The provisions of the present Convention must be respected by the High Contracting Parties under all
circumstances. In case, in time of war, one of the belligerents is not a party to the Convention, its provisions shall
nevertheless remain in force as between the belligerents who are parties thereto.”); 1929 GWS art. 25 (“The
provisions of the present Convention shall be respected by the High Contracting Parties under all circumstances. If,
in time of war, a belligerent is not a party to the Convention, its provisions shall nevertheless remain in force as
between all the belligerents who are parties to the Convention.”).
107 Refer to § 15.1.4 (Application of Treaties on Neutrality and Customary International Law).
108 See, e.g., GPW art. 2 (“Although one of the Powers in conflict may not be a party to the present Convention, the
Powers who are parties thereto shall remain bound by it in their mutual relations.”); GWS-SEA art. 2 (same); GPW
art. 2 (same); GC art. 2 (same); CCW art. 7(1) (“When one of the parties to a conflict is not bound by an annexed
Protocol, the parties bound by this Convention and that annexed Protocol shall remain bound by them in their
mutual relations.”).
109 See CCW art. 7(2) (“Any High Contracting Party shall be bound by this Convention and any Protocol annexed
thereto which is in force for it, in any situation contemplated by Article 1, in relation to any State which is not a
party to this Convention or bound by the relevant annexed Protocol, if the latter accepts and applies this Convention
or the relevant Protocol, and so notifies the Depositary.”); GWS art. 2 (“Although one of the Powers in conflict may
not be a party to the present Convention, the Powers who are parties thereto … shall furthermore be bound by the
Convention in relation to the said Power, if the latter accepts and applies the provisions thereof.”); GWS-SEA art. 2
(same); GPW art. 2 (same); GC art. 2 (same).
110 Refer to § 19.8.2.1 (Hague IV and Customary International Law).
111 Refer to § 18.18 (Reprisals).
112 Refer to § 18.18.3 (Treaty Prohibitions on Reprisals). Consider also VCLT art. 60(5) (“Paragraphs 1 to 3 do not
apply to provisions relating to the protection of the human person contained in treaties of a humanitarian character,
in particular to provisions prohibiting any form of reprisals against persons protected by such treaties.”).
90
Reciprocity is also reflected in the principle of tu quoque, which may limit a State’s
ability to deem unlawful and punish certain conduct by its adversary when that State has chosen
to allow its forces to engage in that same conduct.113
Even if the application of a law of war rule does not depend on reciprocity as a matter of
law, reciprocity may be important as a practical way of encouraging compliance by the adversary
with the law of war.114
3.6.3 Law of War Rules May Incorporate Reciprocity. Apart from affecting whether
rules apply, reciprocity may be incorporated into the operation of particular law of war rules. In
other words, a law of war rule may operate differently depending upon an opponent’s behavior.
3.6.3.1 Reciprocity - “Golden Rule”. A principle of reciprocity may be
understood to be reflected in law of war rules that reflect the golden rule.115 For example, the
treatment of POWs has been based on the principle that POWs should be treated as the Detaining
Power would want its forces held by the enemy to be treated.116 Similarly, during the process of
releasing and repatriating POWs, it is proper to expect that each Party’s conduct with respect to
the repatriation of POWs will be reasonable and broadly commensurate with the conduct of the
other.117
3.6.3.2 Benefits-Burdens Principle in Law of War Rules. In some cases, the law
of war requires that those seeking to obtain certain benefits under the law of war also accept
certain burdens as a condition for receiving those benefits.118 For example, militia and volunteer
corps that seek the privileges of combatant status during international armed conflict must meet
certain conditions (e.g., conducting their operations in accordance with the laws and customs of
war) before receiving such privileges.119 In addition, hospital ships and coastal rescue craft must
113 Refer to § 18.21.2 (Tu Quoque).
114 Refer to § 18.2.2 (Encouraging Reciprocal Adherence by the Adversary).
115 See J. Pictet, The Principles of International Humanitarian Law, 6 INTERNATIONAL REVIEW OF THE RED CROSS
455, 462 (Sept. 1966) (“Humanitarian law receives its impulse from moral science all of which can be summed up in
one sentence, ‘do to others what you would have done to yourself’. This crystallizes the wisdom of nations and is
the secret of happiness, or at least, of the best order of society. This fundamental precept can be found, in an almost
identical form, in all the great religions, Brahmin, Buddhist, Christian, Confucian, Islamic, Jewish and Taoist. It is
also the main prop of the positivists who do not base themselves on precepts of any given religion, but on social
facts, considered objectively, through their own reasoning alone.”).
116 Refer to § 9.2.5 (Reciprocity in the Treatment of POWs).
117 Refer to § 9.37.1 (Agreements on POW Release and Repatriation).
118 See, e.g., Al Warafi v. Obama, 716 F.3d 627, 631-32 (D.C. Cir. 2013) (“The Geneva Conventions and their
commentary provide a roadmap for the establishment of protected status. As the district court found, Al Warafi was
serving as part of the Taliban. The Taliban has not followed the roadmap set forth in the Conventions, and it has not
carried Al Warafi to the destination. … Without compliance with the requirements of the Geneva Conventions, the
Taliban’s personnel are not entitled to the protection of the Convention.”); Jack L. Goldsmith III, Assistant Attorney
General, “Protected Person” Status in Occupied Iraq Under the Fourth Geneva Convention, Mar. 18, 2004, 28
OPINIONS OF THE OFFICE OF LEGAL COUNSEL 35, 53-57 (explaining “the Geneva Conventions’ fundamental
principle that warring entities must accept the Conventions’ burdens in order to claim their benefits.”).
119 Refer to § 4.6 (Other Militia and Volunteer Corps).
91
not be used for military purposes in order to receive their protection from capture and from being
made the object of attack.120 Similarly, cultural property must not be used for military purposes
in order to receive special protection.121
As another example, the rights and duties of belligerents and neutrals under the law of
neutrality may be understood as correlative or reciprocal. For example, a neutral’s valid
assertion of its rights may depend on whether it has fulfilled its corresponding neutral duties.122
3.6.3.3 Law of War Duties That Are Reinforced by Corresponding Duties for the
Enemy. Similarly, the ability of a party to comply with a particular duty may be affected by
whether its opponent has complied with a corresponding duty. For example, the ability of a
party to discriminate in conducting attacks may be affected by whether its adversary has properly
distinguished its military objectives from the civilian population and other protected persons and
objects.123
3.7 APPLYING RULES BY ANALOGY
In some cases, a rule developed specifically for one situation may be a useful and
appropriate standard to apply in a different situation. This is sometimes called an application of
a rule by analogy.
In some cases, there is a treaty requirement to apply rules by analogy; in other cases, it
may be appropriate to apply law of war rules by analogy without a treaty-based requirement to
do so.
3.7.1 Treaty Requirement to Apply Rules by Analogy. The application of law of war
rules by analogy is sometimes required by a treaty provision.
For example, under the 1949 Geneva Conventions, neutral or non-belligerent States must
apply by analogy the rules relating to the treatment of the wounded and sick and of POWs when
interning such persons under their duties of neutrality.124 Similarly, the GC rules for penal
procedures for protected persons in occupied territory apply by analogy to proceedings against
internees who are in the national territory of the Detaining Power.125
3.7.2 Examples of Law of War Rules and Areas in Which Such Rules Have Been
Applied by Analogy. There are other situations in which it may be appropriate to apply law of
war rules by analogy, even though there is no treaty requirement to do so. For example, it may
120 Refer to § 5.18.8.2 (Conditions for the Granting of Special Protection - No Use for Military Purposes).
121 Refer to § 7.12.2.2 (No Use for Military Purposes).
122 Refer to § 15.3.3 (Correlative or Reciprocal Nature of Rights and Duties Under the Law of Neutrality).
123 Refer to § 2.5.5 (Reinforcing Duties - Discriminating in Conducting Attacks and Distinguishing a Party’s Own
Persons and Objects).
124 Refer to § 15.16.3.1 (Provision of POW Treatment and Application of the GWS and GWS-Sea by Analogy).
125 Refer to § 10.29 (Judicial Proceedings Regarding Protected Persons in Occupied Territory or Internees in a
Belligerent’s Home Territory).
92
be appropriate to apply the GWS and GWS-Sea rules for the respectful treatment and handling of
enemy military dead to all persons.126 Other examples of law of war rules and situations in
which it may be appropriate to apply those rules by analogy include: (1) applying jus in bello
rules in certain situations involving neutral or non-belligerent States; (2) applying law of war
rules with a humanitarian purpose in situations outside the context of armed conflict; (3)
applying occupation law provisions for the protection of the civilian population in situations not
constituting belligerent occupation; and (4) applying certain international armed conflict rules in
situations of non-international armed conflict.
3.7.2.1 Jus in Bello Rules and Situations Involving Neutral or Non-Belligerent
States. Although States developed jus in bello rules to address relations between enemies, some
jus in bello rules may be applied by analogy to other situations, such as relations between a
belligerent and a neutral or between co-belligerents. For example, a belligerent might take
feasible precautions to protect the civilian population of a neutral or co-belligerent State from its
military operations, even though such actions might not be required by the law of war.127 In
addition, although the GC excludes certain persons from the definition of protected person based
on their nationality, it may be appropriate to afford such persons the standards of treatment for
protected persons.128
3.7.2.2 Law of War Rules and Military Operations Outside the Context of Armed
Conflict. Because law of war rules often reflect elementary considerations of humanity, it may
be appropriate to apply such standards to military operations occurring outside the context of
armed conflict.129
3.7.2.3 Occupation Law and Situations Not Constituting Belligerent Occupation.
Occupation law may also provide a useful framework for certain situations to which it may not
be strictly applicable.130 For example, it may be appropriate for a State that liberates its ally’s
126 Refer to § 7.7 (Treatment and Handling of Enemy Military Dead).
127 For example, DEPARTMENT OF THE AIR FORCE, HEADQUARTERS PACIFIC AIR FORCES, DIRECTORATE OF
OPERATIONS ANALYSIS, Project CHECO [Contemporary Historical Examination of Current Operations] Report,
Rules of engagement, November 1969-September 1972 (Mar. 1, 1973), reprinted in CONGRESSIONAL RECORD
S3011, S3014 (Mar. 18, 1985) (“The Cambodian incursion plan was a closely held secret timed to coincide with the
President’s announcement. It was not until 27 April [1970] that 7AF was told to start definitive planning. Thus,
there was no time to coordinate a new set of ROE for [neutral] Cambodia. Instead 7AF instructed its pilots to follow
the normal rules for South Vietnam and to exercise extreme vigilance to avoid dropping ordnance on the
noncombatant populace.”); Franklin Roosevelt, message to Winston Churchill, reprinted in WINSTON CHURCHILL,
CLOSING THE RING 467-68 (1985) (“I share fully with you your distress at the loss of life among the French
population incident to our air preparations for ‘Overlord’. I share also with you a satisfaction that every possible
care is being and will be taken to minimise civilian casualties. No possibility of alleviating adverse French opinion
should be overlooked, always provided that there is no reduction of our effectiveness against the enemy at this
crucial time. However regrettable the attendant loss of civilian lives is, I am not prepared to impose from this
distance any restriction on military action by the responsible commanders that in their opinion might militate against
the success of ‘Overlord’ or cause additional loss of life to our Allied forces of invasion.”).
128 Refer to § 10.3.3 (Categories of Nationals Specifically Excluded From the Definition of Protected Person Under
the GC).
129 Refer to § 3.1.1.2 (Applying Law of War Standards as Reflecting Minimum Legal Standards).
130 Refer to § 11.1.3 (Application of Occupation Law to Situations Not Constituting Belligerent Occupation).
93
territory from enemy control to apply by analogy rules from the law of belligerent occupation to
the administration of such territory, pending an agreement with the allied government.131
3.7.2.4 International Armed Conflict Rules and Situations of Non-International
Armed Conflict. Legal rules applicable to international armed conflict may sometimes be applied
by analogy to non-international armed conflict.132
3.8 END OF HOSTILITIES AND THE APPLICATION OF THE LAW OF WAR
In general, law of war rules for the conduct of hostilities cease to apply when hostilities
have ended. However, certain duties that have arisen during hostilities may continue after
hostilities have ended, and certain new duties arise at the end of hostilities.
3.8.1 General Cessation of the Application of the Law of War at the End of Hostilities.
Hostilities end when opposing parties decide to end hostilities and actually do so, i.e., when
neither the intent-based nor act-based tests for when hostilities exist are met.133 Of course, if the
test for the existence of hostilities continues to be met, then hostilities cannot be deemed to have
ceased.134 For example, hostilities may be terminated by:
• an agreement to end hostilities, normally in the form of a treaty of peace;
• unilateral declaration of one of the parties to end the war, provided the other party does
not continue hostilities or otherwise decline to recognize the act of its enemy;
• the complete subjugation of an enemy State and its allies; or
• a simple cessation of hostilities.135
131 Refer to § 11.1.3.2 (Liberation of Friendly Territory).
132 Refer to § 17.2.2.3 (Application of IAC Rules by Analogy).
133 Refer to § 3.4 (When Jus in Bello Rules Apply).
134 David Kris, Assistant Attorney General, Response to Questions Submitted by Members Post Hearing, Questions
Submitted by Mr. Skelton, Reforming the Military Commissions Act of 2006 and Detainee Policy: Hearing Before
the Committee on Armed Services, U.S. House of Representatives, 111th Congress, 1st Session, 77 (Jul. 24, 2009)
(“At a minimum, we believe active hostilities will continue--and detention of enemy forces will be authorized--as
long as the United States is involved in active combat operations against such forces. In reaching the determination
that active hostilities have ceased, we would likely consider factors that have been recognized in international law as
relevant to the existence of an armed conflict, including the frequency and level of intensity of any continuing
violence generated by enemy forces; the degree to which they maintain an organizational structure and operate
according to a plan; the enemy’s capacity to procure, transport and distribute arms; and the enemy’s intent to inflict
violence.”).
135 1956 FM 27-10 (Change No. 1 1976) ¶10 (“The law of land warfare generally ceases to be applicable upon: a.
The termination of a war by agreement, normally in the form of a treaty of peace; or b. The termination of a war by
unilateral declaration of one of the parties, provided the other party does not continue hostilities or otherwise decline
to recognize the act of its enemy; or c. The complete subjugation of an enemy State and its allies, if prior to a or b;
or d. The termination of a declared war or armed conflict by simple cessation of hostilities.”).
94
3.8.1.1 Agreements to End Hostilities. Parties to a conflict often have negotiated
peace treaties to end hostilities.136 Armistice agreements, i.e., temporary cease-fires, are
negotiated to suspend hostilities.137 In addition, the U.N. Security Council may require certain
steps leading to the end of hostilities.138
In drafting and interpreting agreements for the cessation of hostilities, it is important to
understand the rules normally applicable to the cessation of hostilities. These agreements may
refer to provisions in the Geneva Conventions or other law of war instruments. These
agreements may modify or supplement the rules normally applicable to the cessation of
hostilities, e.g., by specifying precisely when a legal obligation is triggered or satisfied.
3.8.1.2 End of Hostilities Absent Written Agreement. Although States often have
concluded agreements to end hostilities, it is possible for hostilities to cease absent a written or
formal agreement. For example, an armed conflict may end when a party is fully subjugated.
It may be difficult to determine when an armed conflict has ceased, as opposed, for
example, to a lull in hostilities during which opposing forces may simply be reconstituting
themselves.139 Hostilities generally would not be deemed to have ceased without an agreement,
unless the conditions clearly indicate that they are not be resumed or there has been a lapse of
time indicating the improbability of resumption.140
3.8.2 Duties Continuing After Hostilities. Under the law of war, certain duties that have
arisen during hostilities may continue after hostilities have ended. For example, POWs are
protected by the GPW from the moment they fall into the power of the enemy until their final
release and repatriation.141 Similarly, protected persons whose release, repatriation, or re-
establishment may take place after the general close of military operations continue to benefit
136 For example, Agreement on Ending the War and Restoring Peace in Viet Nam signed between the Government
of the Democratic Republic of Viet Nam and the Government of the United States, and the Protocols to this
Agreement, Jan. 27, 1973, T.I.A.S. 7542, 935 UNTS 2, 6; General Agreement for Peace in Bosnia and Herzegovina,
Bosn. & Herz.-Croat.-F.R.Y, December 14, 1995, 35 I.L.M. 75 (also known as the Dayton Accords).
137 Refer to § 12.11.1.2 (Armistice as a Suspension of Hostilities and Not a Peace Treaty).
138 Refer to § 12.14 (U.N. Security Council Cease-Fires).
139 Mr. Seward, Secretary of State, to Mr. Goni, Spanish Minister, Jul. 22, 1868, VII MOORE’S DIGEST 336 (“It is
certain that a condition of war can be raised without an authoritative declaration of war, and, on the other hand, the
situation of peace may be restored by the long suspension of hostilities without a treaty of peace being made.
History is full of such occurrences. What period of suspension of war is necessary to justify the presumption of the
restoration of peace has never yet been settled, and must in every case be determined with reference to collateral
facts and circumstances.”).
140 Manley O. Hudson, The Duration of the War Between the United States and Germany, 39 HARVARD LAW
REVIEW 1020, 1029-30 (1926) (“If a war may be ended by a mere cessation of hostilities, the cessation of hostilities
must either be under such conditions that it is clear that they are not to be resumed or there must be a lapse of time
indicating the improbability of resumption.”).
141 Refer to § 9.3.6 (Commencement and Duration of POW Status and Treatment).
95
from the protection of the GC.142 In addition, duties under occupation law may continue after
hostilities have ended.143
3.8.3 Duties Arising at the End of Hostilities. Certain obligations are triggered by the
end of hostilities. For example, the end of hostilities triggers obligations regarding the marking
of minefields, demining, and clearance of unexploded ordnance.144 In addition, POWs and
protected persons, in general, must be released and returned to the party to the conflict to which
they belong.145
3.9 LAW OF WAR DUTIES ALSO APPLICABLE IN PEACE
Some law of war obligations also apply in peace, i.e., even when a State is not engaged in
an armed conflict. For example, States must:
• disseminate information regarding the law of war;146
• train their armed forces in accordance with the law of war;147
• issue instructions and regulations for their armed forces in conformity with the law of
war;148
• review the legality of new weapons;149
• take appropriate measures to prepare for the safeguarding of cultural property;150 and
• take other appropriate measures to ensure the implementation and enforcement of law of
war treaties.151
States that are at peace have obligations under the law of neutrality in relation to States
142 Refer to § 10.3.4 (Commencement and Duration of Protected Person Status).
143 Refer to § 11.3.2 (Duration of GC Obligations in the Case of Occupied Territory).
144 Refer to § 6.12.12.2 (Clearance of Minefields, Mined Areas, Mines, Booby-Traps, and Other Devices After
Hostilities); § 6.20.5 (Obligations Under the CCW Protocol V on Explosive Remnants of War That Are Triggered
by the Cessation of Active Hostilities).
145 Refer to § 9.37 (Release and Repatriation After Hostilities); § 10.35 (Release, Return, Repatriation of Internees
After the Close of Hostilities); § 11.11.8 (Disposition of Accused and Convicted Protected Persons Upon the Close
of Occupation).
146 Refer to § 18.6.1 (General Dissemination and Study of Treaties).
147 Refer to § 18.6.2 (Special Instruction or Training).
148 Refer to § 18.7 (Instructions, Regulations, and Procedures to Implement and Enforce the Law of War).
149 Refer to § 6.2 (DoD Policy of Reviewing the Legality of Weapons).
150 Refer to § 5.18.2.1 (Peacetime Obligations to Prepare for the Safeguarding of Cultural Property).
151 Refer to § 18.1.2 (National Obligations to Implement and Enforce the Law of War).
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that are at war.152
152 Refer to § 15.1.1 (Matters Addressed by the Law of Neutrality).
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IV - Classes of Persons
Chapter Contents
4.1 Introduction
4.2 The Armed Forces and the Civilian Population
4.3 Lawful Combatants and Unprivileged Belligerents
4.4 Rights, Duties, and Liabilities of Combatants
4.5 Armed Forces of a State
4.6 Other Militia and Volunteer Corps
4.7 Levée en Masse
4.8 Rights, Duties, and Liabilities of Civilians
4.9 Military Medical and Religious Personnel
4.10 Rights, Duties, and Liabilities of Military Medical and Religious Personnel
4.11 Authorized Staff of Voluntary Aid Societies
4.12 Staff of a Recognized Aid Society of a Neutral Country
4.13 Auxiliary Medical Personnel
4.14 Personnel Engaged in Duties Related to the Protection of Cultural Property
4.15 Persons Authorized to Accompany the Armed Forces
4.16 Crews of Merchant Marine Vessels or Civil Aircraft
4.17 Spies, Saboteurs, and Other Persons Engaging in Similar Acts Behind
Enemy Lines
4.18 Private Persons Who Engage in Hostilities
4.19 Rights, Duties, and Liabilities of Unprivileged Belligerents
4.20 Children
4.21 Mercenaries
4.22 AP I Provisions on Civil Defense Personnel
4.23 Law Enforcement Officers
4.24 Journalists
4.25 Delegates or Representatives of the Protecting Powers
4.26 ICRC and Other Impartial Humanitarian Organizations
4.27 Determining the Status of Detainees in Cases of Doubt
4.1 INTRODUCTION
This Chapter addresses different classes of persons under the law of war. The law of war
has created a framework of classes of persons to help confine the fighting between opposing
military forces and thereby to help protect the civilian population from the effects of war.1
This Chapter addresses issues relating to various classes of people under the law of war
including: (1) who is included in the various classes, such as “combatant” and “civilian”; (2) the
rights, duties, and liabilities of the persons in each class; and (3) how certain factual categories of
persons, such as journalists, police officers, or child soldiers, fall within various classes and are
treated under the law of war.
1 Refer to § 2.5.1 (Distinction as a Framework of Legal Classes).
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This Chapter briefly addresses specific rules that relate to the rights, duties, and liabilities
of persons in the various classes to illustrate and provide an overview of that class. For more
information about specific rules, practitioners should refer to the cross-referenced sections that
addresses those specific rules.2
4.1.1 General Notes on Terminology for Persons in the Law of War. The terms in the
law of war that describe different classes of people are often used in confusing and contradictory
ways. Although striving to use terms consistently within DoD reduces confusion, understanding
the substantive standards that apply to a person in the applicable circumstances is more important
than using a particular label or a particular system of classification.
4.1.1.1 The Same Term Used With Different Meanings. Sometimes different
meanings are given to the same term. For example, someone might be considered a “combatant”
in the sense that the person may be made the object of attack, but the person would not
necessarily be a “combatant” in the sense that the person is privileged to engage in hostilities.3
Similarly, one source might use the term “noncombatant” to mean all persons who are
not combatants, including persons placed hors de combat and civilians.4 Alternatively, another
source might use the term “noncombatant” to refer specifically to persons who are members of
the armed forces, but who are not combatants.5 In the past, some commentators have used
“noncombatants” of the armed forces to refer to all members of the armed forces serving in
combat service support or sustainment roles.6 In contemporary parlance, however, the term
“noncombatant” should generally be used to mean military medical and religious personnel,7 but
also can include those combatants placed hors de combat.8
2 Refer to § 1.2.3 (Use of Cross-References in This Manual).
3 Refer to § 4.3.2 (Combatant - Notes on Terminology).
4 See, e.g., L.C. GREEN, THE CONTEMPORARY LAW OF ARMED CONFLICT 88 (2nd ed., 2000) (“Nationals of the
adverse party are normally classified as combatants and non-combatants, with the latter including some members of
the armed forces - chaplains, medical personnel and those hors de combat.”); LIEBER CODE art. 19 (“Commanders,
whenever admissible, inform the enemy of their intention to bombard a place, so that the noncombatants, and
especially the women and children, may be removed before the bombardment commences.”).
5 See, e.g., HAGUE IV REG. art. 3 (“The armed forces of the belligerent parties may consist of combatants and
noncombatants. In the case of capture by the enemy, both have the right to be treated as prisoners of war.”).
6 See, e.g., GREENSPAN, MODERN LAW OF LAND WARFARE 56 (“The distinction between combatants and
noncombatants within the armed forces must be taken to correspond to the distinction between fighting troops and
troops in service units. The fighting troops of an army carry out the actual military operations, whereas the service
troops minister to the needs of the former and supply their various requirements. The Hague Regulations do not
define the elements in the two classes, but combatants would include infantry, cavalry, armored troops, and the like,
whose function it is to engage with the enemy; as well as artillery, engineers, signals, and others, whose duty it is to
support such action. Noncombatants would include personnel of the various ‘services’ comprising (inter alia)
medical, chaplains, veterinary, graves, pay, postal, labor, supply, transport, ordnance, provost, legal, and military-
government units.”); GWS COMMENTARY 223 footnote 4 (“In correct terminology, however, ‘armed forces’ include
‘combatants’ (i.e. soldiers bearing arms) and ‘non-combatants’ (who comprise not only medical personnel but also
various other army services not called upon to carry arms).”).
7 Refer to § 4.9 (Military Medical and Religious Personnel).
8 Refer to § 5.10 (Persons Placed Hors de Combat).
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4.1.1.2 Different Terms Used to Describe the Same Concept. Different legal
sources may use different terms to refer to the same class of people under the law of war. For
example, one source might use “belligerent,” whereas another source might use “combatant” to
refer to the same class of people under the law of war.9
4.1.2 Classes and Categories Are Only the Starting Point for Legal Analysis. When
analyzing a person’s rights, duties, and liabilities under the law of war, it is important to analyze
the specific question in light of the applicable facts. Determining what class a person falls into,
such as “combatant,” “civilian,” or “unprivileged belligerent,” may be only the first step in a
legal analysis. For example, whether a person may be the object of attack, may be detained, is
entitled to POW status, or may be punished for their actions are all different questions. Although
these questions are often related to one another and associated with the general classes of
“combatant” and “civilian,” each question requires its own specific analysis. This specific
analysis should be done in each case, applying the legal rules to the facts, rather than deriving an
answer based on a conclusory labeling of a person as, for example, an “enemy combatant.”10
Indeed, some persons might, for some purposes, be treated like “combatants,” but for other
purposes be treated like “civilians.”11
4.2 THE ARMED FORCES AND THE CIVILIAN POPULATION
The law of war has recognized that the population of an enemy State is generally divided
into two classes: the armed forces and the civilian population, also sometimes called,
respectively, “combatants” and “civilians.” This division results from the principle of
distinction.12
4.2.1 Development of the Distinction Between the Armed Forces and the Civilian
Population. A citizen or national of a State that is a party to a conflict, as one of the constituents
of a State that is engaged in hostilities, may be subjected to the hardships of war by an enemy
State.13 However, because the ordinary members of the civilian population make no resistance,
it has long been recognized that there is no right to make them the object of attack.14 Thus,
9 Refer to § 4.3.2 (Combatant - Notes on Terminology).
10 Refer to § 4.18.1 (Private Persons Who Engage in Hostilities - Notes on Terminology).
11 Refer to § 4.2.3 (Mixed Cases).
12 Refer to § 2.5 (Distinction).
13 See, e.g., Johnson v. Eisentrager, 339 U.S. 763, 772-73 (1950) (“The alien enemy is bound by an allegiance which
commits him to lose no opportunity to forward the cause of our enemy; hence the United States, assuming him to be
faithful to his allegiance, regards him as part of the enemy resources. It therefore takes measures to disable him
from commission of hostile acts imputed as his intention because they are a duty to his sovereign.”); LIEBER CODE
art. 21 (“The citizen or native of a hostile country is thus an enemy, as one of the constituents of the hostile state or
nation, and as such is subjected to the hardships of the war.”).
14 See LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW 204 (§57) (“Those private subjects of the belligerents
who do not directly or indirectly belong to the armed forces do not take part in it; they do not attack and defend; and
no attack ought therefore to be made upon them.”); G. SHERSTON BAKER, II HALLECK’S INTERNATIONAL LAW 15-16
(20.3) (1908) (“Feeble old men, women, and children, and sick persons, come under the general description of
enemies, and we have certain rights over them as members of the community with which we are at war; but, as they
are enemies who make no resistance, we have no right to maltreat their persons, or to use any violence toward them,
much less to take their lives.”); LIEBER CODE arts. 22, 23, 25 (explaining that protection of the “unarmed citizen,”
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States have departed from ancient and medieval practices of war between entire peoples, and
instead, as much as possible, have treated war as a contention between the professional military
forces of warring States.15 This separation of the armed forces and the civilian population has
greatly mitigated the evils of war.16
4.2.2 No Person May Claim the Distinct Rights Afforded to Both Combatants and
Civilians at the Same Time. The classes of combatants and civilians have distinct rights, duties,
and liabilities; no person may claim the distinct rights afforded both classes at the same time.17
For example, a person may not claim the combatant’s right to attack enemy forces while also
claiming the civilian’s right not to be made the object of attack.18
4.2.3 Mixed Cases. Certain classes of persons do not fit neatly within the dichotomy of
the armed forces and the civilian population, i.e., combatants and civilians. Each of these
the “inoffensive individual,” or the “inoffensive citizen of the hostile country” is the rule) (emphasis added);
VATTEL, THE LAW OF NATIONS 282 (3.8.145) (“Women, children, feeble old men, and the sick … these are enemies
who make no resistance, and consequently the belligerent has no right to maltreat or otherwise offer violence to
them, much less to put them to death.”).
15 See, e.g., LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW 204 (§57) (“During antiquity, and the greater part
of the Middle Ages, war was a contention between the whole populations of the belligerent States. In time of war
every subject of one belligerent, whether an armed and fighting individual or not, whether man or woman, adult or
infant, could be killed or enslaved by the other belligerent at will. But gradually a milder and more discriminating
practice grew up, and nowadays the life and liberty of such private subjects of belligerents as do not directly or
indirectly belong to their armed forces, and, with certain exceptions, their private property, are protected by
International Law.”); LIEBER CODE art. 22 (“Nevertheless, as civilization has advanced during the last centuries, so
has likewise steadily advanced, especially in war on land, the distinction between the private individual belonging to
a hostile country and the hostile country itself, with its men in arms. The principle has been more and more
acknowledged that the unarmed citizen is to be spared in person, property, and honor as much as the exigencies of
war will admit.”).
16 See SPAIGHT, WAR RIGHTS ON LAND 37 (“The separation of armies and peaceful inhabitants into two distinct
classes is perhaps the greatest triumph of International Law. Its effect in mitigating the evils of war has been
incalculable.”); G. SHERSTON BAKER, II HALLECK’S INTERNATIONAL LAW 20-22 (20.3) (1908) (“But afterwards in
Italy, and more particularly during the lawless confusion of the feudal ages, hostilities were carried on by all classes
of persons, and everyone capable of being a soldier was regarded as such, and all the rights of war attached to his
person. But as wars are now carried on by regular troops, or, at least, by forces regularly organised, the peasants,
merchants, manufacturers, agriculturists, and, generally, all public and private persons, who are engaged in the
ordinary pursuits of life, and take no part in military operations, have nothing to fear from the sword of the enemy.
So long as they refrain from all hostilities, pay the military contributions which may be imposed on them and quietly
submit to the authority of the belligerent who may happen to be in the military possession of their country, they are
allowed to continue in the enjoyment of their property, and in the pursuit of their ordinary avocations. This system
has greatly mitigated the evils of war, … .”).
17 See, e.g., 1956 FM 27-10 (Change No. 1 1976) ¶60 (dividing into “prisoners of war” and “the civilian
population,” and noting that “[p]ersons in each of the foregoing categories have distinct rights, duties, and
disabilities.”); 1940 RULES OF LAND WARFARE ¶8 (“The enemy population is divided in war into two general
classes, known as, the armed forces and the peaceful population. Both classes have distinct rights, duties, and
disabilities, and no person can belong to both classes at one and the same time.”); 1934 RULES OF LAND WARFARE
¶8 (same); 1914 RULES OF LAND WARFARE ¶29 (same).
18 See 1958 UK MANUAL ¶86 (“It is one of the purposes of the law of war to ensure that an individual who belongs
to one class or the other shall not be permitted to enjoy the privileges of both. Thus he must not be allowed to kill or
wound members of the army of the opposing belligerent and subsequently, if captured, to claim that he is a peaceful
citizen.”).
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particular classes has some attributes of combatant status and some attributes of civilian status; in
certain respects persons in these classes are treated like combatants, but in other respects they are
treated like civilians. These classes may be classified into three groups: (1) certain personnel
engaged in humanitarian duties; (2) certain authorized supporters of the armed forces; and (3)
unprivileged belligerents.
4.2.3.1 Certain Personnel Engaged Humanitarian Duties. Certain categories of
personnel have humanitarian duties that involve them in hostilities but also entitle them to
special protections:
• military medical and religious personnel;19
• authorized staff of voluntary aid societies;20
• staff of a recognized aid society of a neutral country;21
• auxiliary medical personnel;22 and
• personnel engaged in the protection of cultural property.23
4.2.3.2 Certain Authorized Supporters of the Armed Forces. Certain categories of
persons are not members of the armed forces, but are nonetheless authorized to support the
armed forces in the fighting:
• persons authorized to accompany the armed forces, but who are not members thereof;24
and
• members of the crews of merchant marine vessels or civil aircraft of a belligerent.25
4.2.3.3 Unprivileged Belligerents. Unprivileged belligerents generally are subject
to the liabilities of both combatant and civilian status, and include:26
• persons engaging in spying, sabotage, and similar acts behind enemy lines;27 and
• private persons engaging in hostilities.28
19 Refer to § 4.9 (Military Medical and Religious Personnel).
20 Refer to § 4.11 (Authorized Staff of Voluntary Aid Societies).
21 Refer to § 4.12 (Staff of a Recognized Aid Society of a Neutral Country).
22 Refer to § 4.13 (Auxiliary Medical Personnel).
23 Refer to § 4.14.1 (Personnel Engaged in the Protection of Cultural Property).
24 Refer to § 4.15 (Persons Authorized to Accompany the Armed Forces).
25 Refer to § 4.16 (Crews of Merchant Marine Vessels or Civil Aircraft).
26 Refer to § 4.3.4 (Types of Unprivileged Belligerents).
27 Refer to § 4.17 (Spies, Saboteurs, and Other Persons Engaging in Similar Acts Behind Enemy Lines).
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4.3 LAWFUL COMBATANTS AND UNPRIVILEGED BELLIGERENTS
In addition to distinguishing between the armed forces and the civilian population, the
law of war also distinguishes between “privileged” and “unprivileged,” or “lawful” and
“unlawful” combatants. As the Supreme Court has explained:
Lawful combatants are subject to capture and detention as prisoners of war by
opposing military forces. Unlawful combatants are likewise subject to capture
and detention, but in addition they are subject to trial and punishment by military
tribunals for acts which render their belligerency unlawful.29
“Unlawful combatants” or “unprivileged belligerents” are persons who, by engaging in
hostilities, have incurred one or more of the corresponding liabilities of combatant status (e.g.,
being made the object of attack and subject to detention), but who are not entitled to any of the
distinct privileges of combatant status (e.g., combatant immunity and POW status).30
4.3.1 “Unprivileged Belligerents” as a Category in Treaty Law. States have, in a few
cases, explicitly recognized in treaties certain categories of unprivileged belligerents, such as
spies and saboteurs.31 However, States have generally refrained from explicitly recognizing
unprivileged belligerents as a class in treaties in the way that classes of lawful combatants have
been defined.32
Law of war treaties have been understood to reflect restrictions on the conduct of
hostilities by States,33 and States have been reluctant to conclude treaties to afford unprivileged
enemy belligerents the distinct privileges of POW status or the full protections afforded
civilians.34
28 Refer to § 4.18 (Private Persons Who Engage in Hostilities).
29 Ex parte Quirin, 317 U.S. 1, 31 (1942). See also Hamdi v. Rumsfeld, 542 U.S. 507, 518 (2004) (plurality) (“The
capture and detention of lawful combatants and the capture, detention, and trial of unlawful combatants, by
‘universal agreement and practice,’ are ‘important incident[s] of war.’”) (quoting Ex parte Quirin at 28, 30).
30 Refer to § 4.19 (Rights, Duties, and Liabilities of Unprivileged Belligerents).
31 See, e.g., HAGUE IV REG. arts. 29-31 (defining the category of spy and regulating the treatment of captured spies);
GC art. 5 (regulating the treatment of certain protected persons “detained as a spy or saboteur, or as a person under
definite suspicion of activity hostile to the security of the Occupying Power”). See also GC COMMENTARY 5 (“It
may, nevertheless, seem rather surprising that a humanitarian Convention should tend to protect spies, saboteurs or
irregular combatants. Those who take part in the struggle while not belonging to the armed forces are acting
deliberately outside the laws of warfare. Surely they know the dangers to which they are exposing themselves. It
might therefore have been simpler to exclude them from the benefits of the Convention, if such a course had been
possible, but the terms espionage, sabotage, terrorism, banditry and intelligence with the enemy, have so often been
used lightly, and applied to such trivial offences, that it was not advisable to leave the accused at the mercy of those
detaining them.”).
32 See, e.g., GWS art. 13; GWS-SEA art. 13; GPW art. 4.
33 Refer to § 1.3.3.1 (Law of War as Prohibitive Law).
34 See, e.g., IIA FINAL REPORT OF THE DIPLOMATIC CONFERENCE OF GENEVA OF 1949 433 (ICRC representative
explaining that “[t]he present Conference was engaged in framing a Convention to protect members of armed forces
and similar categories of persons, such as members of organized resistance movements, and another convention to
103
Although seldom explicitly recognized as a class in law of war treaties, the category of
unprivileged belligerent may be understood as an implicit consequence of creating the classes of
lawful combatants and peaceful civilians.35 The concept of unprivileged belligerency, i.e., the
set of legal liabilities associated with unprivileged belligerents, may be understood in opposition
to the rights, duties, and liabilities of lawful combatants and peaceful civilians. Unprivileged
belligerents include lawful combatants who have forfeited the privileges of combatant status by
engaging in spying or sabotage, and private persons who have forfeited one or more of the
protections of civilian status by engaging in hostilities.36
4.3.2 Combatant - Notes on Terminology.
4.3.2.1 “Combatant” and “Belligerent”. “Combatant” and “belligerent” have
sometimes been used interchangeably and, in this usage, they generally describe individuals who
are not “civilians.”
“Belligerent,” however, has also sometimes used to describe States and to contrast such
States with “neutral” or “non-belligerent” States.37
“Belligerent” has also been used to contrast
armed groups that have “belligerent rights” with armed groups that lack such rights, such as
“insurgents.”38
4.3.2.2 “Lawful,” “Privileged,” and “Qualified”. The distinction between
“lawful” and “unlawful” combatants has sometimes been called a distinction between
protect civilians. Although the two Conventions might appear to cover all the categories concerned, irregular
belligerents were not actually protected.”); id. at 612 (Swiss representative taking the view that “[i]n regard to the
legal status of those who violated the laws of war, the [Civilians] Convention could not of course cover criminals or
saboteurs.”); id. at 621 (UK representative rejecting a draft which “would mean that persons who were not entitled
to protection under the Prisoners of War Convention would receive exactly the same protection by virtue of the
Civilians Convention, so that all persons participating in hostilities would be protected, whether they conformed to
the laws of war or not. … The whole conception of the Civilians Convention was the protection of civilian victims
of war and not the protection of illegitimate bearers of arms, who could not expect full protection under rules of war
to which they did not conform. Such persons should no doubt be accorded certain standards of treatment, but should
not be entitled to all the benefits of the Convention.”).
35 See, e.g., 10 U.S.C. § 948a (“The term ‘unprivileged enemy belligerent’ means an individual (other than a
privileged belligerent) who” engages in certain conduct); Ex parte Quirin, 317 U.S. 1, 35 (1942) (“Our Government,
by thus defining lawful belligerents entitled to be treated as prisoners of war, has recognized that there is a class of
unlawful belligerents not entitled to that privilege, including those who, though combatants, do not wear ‘fixed and
distinctive emblems.’”).
36 Refer to § 4.3.4 (Types of Unprivileged Belligerents).
37 Refer to § 15.1.2 (Classification of States as Belligerent, Neutral, or Non-Belligerent).
38 See, e.g., Memorandum submitted in United States v. Shakur, 690 F. Supp. 1291 (S.D.N.Y. 1988), III
CUMULATIVE DIGEST OF UNITED STATES PRACTICE IN INTERNATIONAL LAW 1981-88 3436, 3448 (“The concept of
‘insurgency’ was traditionally used to describe a conflict that did not meet the rigid standards of customary
international law for recognition of belligerency.”); Anthony Eden, Secretary of State for Foreign Affairs, United
Kingdom, Oral Answers to Questions, Dec. 8, 1937, HANSARD 330 HOUSE OF COMMONS DEBATES § 357 (“His
Majesty’s Ambassador at Hendaye has been instructed to inform the Salamanca authorities that as belligerent rights
have not been recognised to either party in the Spanish conflict. His Majesty’s Government are not prepared to
admit their right to declare any such blockade.”). Refer to § 3.3.3 (State Recognition of Armed Groups as
Belligerents).
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“privileged” and “unprivileged” belligerents, i.e., distinguishing between persons who are
entitled to the privileges of combatant or belligerent status, and those who are not.39 This
distinction has also sometimes been called a distinction between “qualified” and “unqualified”
belligerents, i.e., distinguishing between persons who have met the qualifications to receive the
privileges of combatant status and those who have not.40
4.3.2.3 “Combatant” Used Without Modification. “Combatant” and
“belligerent,” when used without modification (such as “lawful” or “unlawful,” or “privileged”
or “unprivileged”), have often referred implicitly to lawful or privileged combatants.41
However, in some cases, “combatant” or “belligerent” has been used to refer to all persons who
engage in hostilities, without taking a position as to whether they are entitled to receive the
privileges of combatant status.
4.3.2.4 General Usage of “Combatant” in This Manual. This manual generally
uses “combatant” to refer implicitly to lawful or privileged combatants.
This manual generally uses the term “unprivileged belligerent” (instead of, e.g.,
“unlawful combatant,” “unlawful belligerent,” “unprivileged combatant,” etc.) to refer to persons
who are subject to one or more of the liabilities of combatant status, but are not entitled to
receive its distinct privileges.
4.3.3 Types of Lawful Combatants. Three classes of persons qualify as “lawful” or
“privileged” combatants:
• members of the armed forces of a State that is a party to a conflict, aside from certain
categories of medical and religious personnel;42
• under certain conditions, members of militia or volunteer corps that are not part of the
armed forces of a State, but belong to a State;43 and
• inhabitants of an area who participate in a kind of popular uprising to defend against
foreign invaders, known as a levée en masse.44
39 See, e.g., 1958 UK MANUAL ¶96 (“Should regular combatants fail to comply with these four conditions, they may
in certain cases become unprivileged belligerents. This would mean that they would not be entitled to the status of
prisoners of war upon their capture.”); Richard R. Baxter, So-Called ‘Unprivileged Belligerency’: Spies, Guerillas,
and Saboteurs, 28 BRITISH YEAR BOOK OF INTERNATIONAL LAW 323 (1951); LIEBER CODE art. 49 (describing who
is “exposed to the inconveniences as well as entitled to the privileges of a prisoner of war”).
40 See, e.g., JAMES M. SPAIGHT, AIRCRAFT IN WAR 51 (1914) (referring to “that outlaw of war law—the unqualified
belligerent”); HAGUE IV REG. arts. 1-3 (describing who meets “[t]he Qualifications of Belligerents”).
41 See, e.g., AP I art. 43(2) (describing “combatants” as those who “have the right to participate directly in
hostilities.”).
42 Refer to § 4.5 (Armed Forces of a State).
43 Refer to § 4.6 (Other Militia and Volunteer Corps).
44 Refer to § 4.7 (Levée en Masse).
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4.3.4 Types of Unprivileged Belligerents. Unprivileged belligerents may generally be
classified into two categories that may be distinguished from one another by the presence or
absence of State authorization:
• persons who have initially qualified as combatants (i.e., by falling into one of the three
categories mentioned above), but who have acted so as to forfeit the privileges of
combatant status by engaging in spying or sabotage;45 and
• persons who never meet the qualifications to be entitled to the privileges of combatant
status, but who have, by engaging in hostilities, incurred the corresponding liabilities of
combatant status (i.e., forfeited one or more of the protections of civilian status).46
These two categories of unprivileged belligerents generally receive the same treatment.47
However, the distinction that the first category has State authorization, while the second category
does not, may be important and create different legal results. For example, the combatant who
spies regains the entitlement to the privileges of combatant status upon returning to friendly
lines, but the private person who spies cannot regain a status to which the person was never
entitled.48 Similarly, acts of unprivileged belligerency on the high seas may constitute piracy, a
crime under international law, although similar acts by persons acting under State authority, even
if they were not members of the armed forces, could not constitute piracy.49
4.4 RIGHTS, DUTIES, AND LIABILITIES OF COMBATANTS
Combatants have a special legal status, i.e., certain rights, duties, and liabilities. As
discussed below, combatants may engage in hostilities and are liable to being made the object of
attack by enemy combatants. Combatants must conduct their operations in accordance with the
law of war. They have the right to POW status if they fall into the power of the enemy during
international armed conflict. Combatants have legal immunity from domestic law for acts done
under military authority and in accordance with the law of war.
4.4.1 Combatants - Conduct of Hostilities. In general, combatants may engage in
hostilities and may be made the object of attack by enemy combatants.50 However, combatants
placed hors de combat must not be made the object of attack.51
Combatants must conduct their operations in accordance with the law of war. For
example, combatants must take certain measures to distinguish themselves from the civilian
population.52 Combatants also may not kill or wound the enemy by resort to perfidy.53
45 Refer to § 4.17 (Spies, Saboteurs, and Other Persons Engaging in Similar Acts Behind Enemy Lines).
46 Refer to § 4.18 (Private Persons Who Engage in Hostilities).
47 Refer to § 4.19 (Rights, Duties, and Liabilities of Unprivileged Belligerents).
48 Refer to § 4.17.5 (Spying and Sabotage - Forfeiture of the Privileges of Combatant Status).
49 Refer to § 4.18.5 (Private Persons Who Engage in Hostilities and the Law of War).
50 Refer to § 5.8 (Combatants).
51 Refer to § 5.10 (Persons Placed Hors de Combat).
52 Refer to § 5.5.8 (Obligation of Combatants to Distinguish Themselves When Conducting Attacks).
106
Combatants must only direct their attacks against military objectives.54 Combatants must take
feasible precautions in conducting attacks to reduce the risk of harm to the civilian population.55
Chapter V addresses in detail the rules that combatants must follow in the conduct of hostilities.
4.4.2 Combatants - POW Status During Detention. Combatants are liable to capture and
detention by enemy combatants, but are entitled to POW status when they fall into the power of
the enemy during international armed conflict. POWs, like all detained individuals, must be
treated humanely.56 In addition, POWs are afforded a variety of privileges in detention in
accordance with the GPW, such as camp canteens, advances of pay, and permission to wear their
badges of rank, nationality, or decorations.57 POWs also have duties in detention, such as
identifying themselves to their captors,58 and they are subject to the laws, regulations, and orders
of the Detaining Power.59 Chapter IX addresses in detail the treatment of POWs and their duties.
In general, POWs shall be released and repatriated without delay after the cessation of
active hostilities.60 However, seriously wounded, injured, or sick POWs should be returned
before the end of hostilities.61 In addition, after the hostilities have ended, certain POWs may be
held in connection with criminal proceedings.62
In general, combatants retain their right to POW status and treatment, even if they are
alleged to have committed crimes before capture.63 For example, POWs are entitled to a variety
of rights in relation to judicial proceedings against them.64 In addition, POWs serving
disciplinary punishment shall continue to receive the benefits of the GPW, except insofar as
these benefits are necessarily rendered inapplicable by the mere fact that the POW is confined.65
Combatants captured while engaged in spying or sabotage forfeit their entitlement to
POW status.66 In cases of doubt as to whether a detainee is entitled to POW status, that person
53 Refer to § 5.22 (Treachery or Perfidy Used to Kill or Wound).
54 Refer to § 5.5 (Rules on Conducting Assaults, Bombardments, and Other Attacks).
55 Refer to § 5.11 (Feasible Precautions in Conducting Attacks to Reduce the Risk of Harm to Protected Persons and
Objects).
56 Refer to § 9.5 (Humane Treatment and Basic Protections for POWs).
57 Refer to § 9.17 (Canteens for POWs); § 9.18.3 (Advance of Pay); § 9.22.4 (Rank and Age of POWs).
58 Refer to § 9.8 (Interrogation of POWs).
59 Refer to § 9.26.1 (POWs Subject to the Laws, Regulations, and Orders in Force in the Armed Forces of the
Detaining Power).
60 Refer to § 9.37 (Release and Repatriation After Hostilities).
61 Refer to § 9.36.1 (Direct Repatriation of Seriously Wounded, Injured, or Sick POWs).
62 Refer to § 9.37.4.3 (POWs Undergoing Criminal Proceedings for an Indictable Offense).
63 Refer to § 9.26.4 (Retention of Benefits of the GPW Even if Prosecuted for Pre-Capture Acts).
64 Refer to § 9.28 (Judicial Proceedings and Punishment).
65 Refer to § 9.27.6.2 (Retention of the Benefits of the GPW While Undergoing Disciplinary Punishment).
66 Refer to § 4.17.5 (Spying and Sabotage - Forfeiture of the Privileges of Combatant Status).
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should be afforded the protections of POW status until their status has been determined by a
competent tribunal.67
4.4.3 Combatants - Legal Immunity From a Foreign State’s Domestic Law. International
law affords combatants a special legal immunity from the domestic law of the enemy State for
their actions done in accordance with the law of war.68 This legal immunity is sometimes called
the “combatant’s privilege” or “combatant immunity.” This means that a combatant’s “killing,
wounding, or other warlike acts are not individual crimes or offenses,”69 if they are done under
military authority and are not prohibited by the law of war.70 Similarly, a combatant’s warlike
acts done under military authority and in accordance with the law of war also do not create civil
liability.71
Combatants lack legal immunity from an enemy State’s domestic law for acts that are
prohibited by the law of war.72 Also, combatants lack legal immunity from an enemy State’s
domestic law while engaging in spying or sabotage.73 Combatants, however, must receive a fair
and regular trial before any punishment.74
67 Refer to § 4.27.2 (POW Protections for Certain Persons Until Status Has Been Determined).
68 This legal immunity would also be applicable with respect to neutral States to the extent they sought to exercise
jurisdiction over the conduct of belligerents. Traditionally, however, neutral States generally did not assert
jurisdiction over conduct committed between belligerents. Refer to § 18.21.1 (Jurisdiction Over War Crimes).
69 LIEBER CODE art. 57. See also Johnson v. Eisentrager, 339 U.S. 763, 793 (1950) (Black, J., dissenting)
(explaining that “legitimate ‘acts of warfare,’ however murderous, do not justify criminal conviction” and that “it is
no ‘crime’ to be a soldier.”); WINTHROP, MILITARY LAW & PRECEDENTS 778 (“The State is represented in active
war by its contending army, and the laws of war justify the killing or disabling of members of the one army by those
of the other in battle or hostile operations.”); Arce v. State, 202 S.W. 951 (Texas Court of Criminal Appeals 1918)
(reversing homicide conviction of Mexican soldiers prosecuted in connection with hostilities between the United
States and Mexico). Consider AP I art. 43(2) (“combatants … have the right to participate directly in hostilities.”).
70 See United States v. List, et al. (The Hostage Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 1236 (“acts
done in time of war under the military authority of an enemy cannot involve criminal liability on the part of officers
or soldiers if the acts are not prohibited by the conventional or customary rules of war.”); Daniel Webster,
Department of State, Letter to John G. Crittenden, Attorney General, Mar. 15, 1841, reprinted in THE DIPLOMATIC
AND OFFICIAL PAPERS OF DANIEL WEBSTER, WHILE SECRETARY OF STATE 134-35 (1848) (explaining “[t]hat an
individual forming part of a public force, and acting under the authority of his Government, is not to be held
answerable, as a private trespasser or malefactor, is a principle of public law sanctioned by the usages of all civilized
nations”).
71 See Freeland v. Williams, 131 U.S. 405, 416 (1889) (“Ever since the case of Dow v. Johnson, 100 U.S. 158, the
doctrine has been settled in the courts that in our late civil war, each party was entitled to the benefit of belligerent
rights, as in the case of public war, and that, for an act done in accordance with the usages of civilized warfare,
under and by military authority of either party, no civil liability attached to the officers or soldiers who acted under
such authority.”); Dow v. Johnson, 100 U.S. 158, 165 (1879) (“There would be something singularly absurd in
permitting an officer or soldier of an invading army to be tried by his enemy, whose country it had invaded. The
same reasons for his exemption from criminal prosecution apply to civil proceedings.”).
72 See United States, et al. v. Göring, et al., Judgment, I TRIAL OF THE MAJOR WAR CRIMINALS BEFORE THE IMT
223 (“He who violates the laws of war cannot obtain immunity while acting in pursuance of the authority of the state
if the state in authorizing action moves outside its competence under international law.”).
73 Refer to § 4.17.3 (Spying and Sabotage - Forfeiture of the Privileges of Combatant Status).
74 Refer to § 9.28.4 (Rights of Defense and Trial Procedure).
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4.4.3.1 Combatants - Legal Immunity and POW Status. The “combatant’s
privilege” from liability under domestic law has been associated with POW status.75 In that
vein, U.S. courts have inferred from provisions of the GPW the combatant’s privilege against
being prosecuted by capturing States.76 However, the legal immunity that combatants may be
afforded is not the same as POW status. For example, a combatant’s conduct may be protected
by legal immunities even when that person is not in the power of the enemy and thus is not a
POW. As another example of how POW status and legal immunity may differ, the GPW
generally affords the same treatment to all classes of POWs identified in Article 4. However, not
all the categories of POWs identified in Article 4 of the GPW, such as persons authorized to
accompany the armed forces, receive the general license to commit belligerent acts that is
afforded members of the armed forces.77
4.4.3.2 Combatants - Legal Immunity and Sovereignty. In addition to being
associated with humanitarian principles governing the treatment of POWs, the combatant’s
privilege has also been viewed as an application of the immunity that international law affords
States from each other’s jurisdiction.78 In this view, “the act of the soldier who conforms to the
law of war and does not engage in private acts of warfare is an act of state depriving the enemy
75 See, e.g., Memorandum submitted in United States v. Shakur, 690 F. Supp. 1291 (S.D.N.Y. 1988), III
CUMULATIVE DIGEST OF UNITED STATES PRACTICE IN INTERNATIONAL LAW 1981-88 3436, 3451 (“It is well-
accepted that individuals who enjoy the status of prisoner of war are generally immune from prosecution for
legitimate acts of war in international armed conflicts.”); ALLAN ROSAS, THE LEGAL STATUS OF PRISONERS OF WAR:
A STUDY IN INTERNATIONAL HUMANITARIAN LAW APPLICABLE IN ARMED CONFLICTS 305 (1976) (“there has
traditionally been a close relationship between the concept of prisoners of war and that of lawful combatants.”);
LIEBER CODE art. 56 (“A prisoner of war is subject to no punishment for being a public enemy, nor is any revenge
wreaked upon him by the intentional infliction of any suffering, or disgrace, by cruel imprisonment, want of food,
by mutilation, death, or any other barbarity.”).
76 See United States v. Lindh, 212 F. Supp. 2d 541, 553 (E.D. Va. 2002) (memorandum opinion) (interpreting
articles 87 and 99 of GPW to “make clear that a belligerent in a war cannot prosecute the soldiers of its foes for the
soldiers’ lawful acts of war”); United States v. Khadr, 717 F.Supp.2d. 1215, 1222 footnote 7 (USCMCR 2007)
(same); United States v. Pineda, 2006 U.S. Dist. LEXIS 17509, 6-8 (D.D.C. Mar. 23, 2006) (D.D.C. 2006) (same).
See also United States v. Noriega, 746 F. Supp. 1506, 1529 (S.D. Fla. 1990) (“As is evident from its text and
construed as a whole, the essential purpose of the Geneva Convention Relative to the Treatment of Prisoners of War
is to protect prisoners of war from prosecution for conduct which is customary in armed conflict.”).
77 ALLAN ROSAS, THE LEGAL STATUS OF PRISONERS OF WAR: A STUDY IN INTERNATIONAL HUMANITARIAN LAW
APPLICABLE IN ARMED CONFLICTS 305 (1976) (“The relationship between the concepts of lawful combatants and
prisoners of war has been said to arise from the fact that lawful combatants are always entitled to prisoner-of-war
status, while the reverse is not necessarily true, as there are categories of persons entitled to the status of prisoners of
war who as civilians enjoy no general license to commit belligerent acts.”).
78 Cf. United States v. Thierichens, 243 F. 419, 420 (E.D. Pa. 1917) (“The well-settled rule that, under the comity
existing between nations, the public armed ship of a friendly nation, acting under the immediate and direct command
of the sovereign power, is not to be interfered with by the courts of a foreign state, is based upon the principle that, if
the courts did attempt to assume jurisdiction over such vessel, it would require the sovereign of the nation to which
the vessel belongs to be impleaded in the court from which the process issued, and, by common consent of nations,
such situations could not arise without interference with the power and dignity of the foreign sovereign. Therefore
the courts will not assume jurisdiction over such vessel or its officers, while acting as such, but leave controversies
arising out of the acts of the vessel, and its officers, while acting in their official character, for settlement through
diplomatic channels.”).
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state of jurisdiction.”79 This view of the combatant’s privilege requires that combatants act
under the commission of a belligerent State.80 This view also reflects the principle that only
States may authorize the resort to force.81
4.4.4 Nationality and Combatant Status.
4.4.4.1 Nationals of Neutral States in Enemy Forces. Members of enemy armed
forces may include nationals of neutral or non-belligerent States. For example, the U.S. armed
forces include many foreign nationals, and the United States could be engaged in hostilities when
those foreign nationals’ home States are not. Nationals of a neutral or non-belligerent State who
are members of the armed forces of a belligerent State should be treated like other members of
that State’s armed forces.82 For example, such nationals are entitled to POW status if they fall
into the power of the enemy during international armed conflict.83
4.4.4.2 Nationals of a State Who Join Enemy Forces. The special privileges that
international law affords combatants generally do not apply between a national and his or her
State of nationality.84 For example, provisions of the GPW assume that POWs are not nationals
of the Detaining Power.85 Thus, international law does not prevent a State from punishing its
79 Richard Baxter, The Municipal and International Law Basis of Jurisdiction over War Crimes, 28 BRITISH YEAR
BOOK OF INTERNATIONAL LAW 382, 385 (1951). See also Hans Kelsen, Collective and Individual Responsibility in
International Law with Particular Regard to the Punishment of War Criminals, 31 CALIFORNIA LAW REVIEW 530,
549 (1943) (“That a State violates international law if it punishes as a criminal, according to its national law, a
member of the armed forces of the enemy for an act of legitimate warfare, can be explained only by the fact that the
State by so doing makes an individual responsible for an act of another State. According to international law, the act
in question must be imputed to the enemy State and not to the individual who in the service of his State has
performed the act. It cannot be considered as a crime of the individual because it must not be considered as his act
at all.”); LIEBER CODE art. 41 (“All municipal law of the ground on which the armies stand, or of the countries to
which they belong, is silent and of no effect between armies in the field.”).
80 See Wharton, Com. Am. Law, § 221, VII MOORE’S DIGEST 175 (“It is necessary in order to place the members of
an army under the protection of the law of nations, that it should be commissioned by a state. … Hence, all civilized
nations have agreed in the position that war to be a defence to an indictment for homicide or other wrong, must be
conducted by a belligerent state, and that it can not avail voluntary combatants not acting under the commission of a
belligerent.”).
81 Refer to § 1.11.1.1 (Competent Authority (Right Authority) to Wage War for a Public Purpose).
82 Refer to § 15.6.2.1 (No More Severe Treatment Than Nationals of an Opposing Belligerent State).
83 LEVIE, POWS 74-75 (“Normally, the nationality of the individual falling within one of the categories enumerated
in Article 4 is that of the belligerent Power for which he is fighting. However, he may have the nationality of a
neutral, or of an ally of the belligerent in whose armed forces he is serving at the time that he falls into the power of
the enemy--or even of the adverse Party, or one of its allies. Does this affect his entitlement to prisoner-of-war
status? Apparently there is no dispute with respect to the entitlement to prisoner-of-war status of an individual who
is a national of a neutral State or of a State which is an ally of the belligerent in whose armed forces he is serving.”).
84 Compare § 10.3.3.1 (A State’s Own Nationals).
85 See, e.g., GPW art. 87 (“When fixing the penalty, the courts or authorities of the Detaining Power shall take into
consideration, to the widest extent possible, the fact that the accused, not being a national of the Detaining Power, is
not bound to it by any duty of allegiance, and that he is in its power as the result of circumstances independent of his
own will.”). Refer to § 9.26.6 (Prohibited Penalties); § 9.28.6 (Death Sentences).
110
nationals whom it may capture among the ranks of enemy forces.86 This rule is significant in
non-international armed conflicts in which a State is fighting a rebel group composed of its own
citizens.87
Although, as a matter of international law, nationals may not assert the privileges of
combatant status against their own State, they may be subject to the liabilities of combatant
status in relation to their own State under that State’s domestic law. For example, under U.S.
law, U.S. nationals who join enemy forces have been subject to the liabilities of combatant
status, such as potentially being made the object of attack or detained.88
4.4.4.3 Nationals of Allied or Co-Belligerent States. Nationals of an allied or co-
belligerent State who are serving with enemy forces are in a position that is similar to the
position of nationals of a State who are serving with enemy forces. If the nationals of an allied
or co-belligerent State who are serving with enemy forces are captured by a State, they may be
transferred to their State of nationality (i.e., the co-belligerent or allied State), which is not
required to afford them POW status.89 However, U.S. practice as the Detaining Power in this
situation has been to afford POW treatment to such individuals if they claim such protection.90
86 See Public Prosecutor v. Oie Hee Koi and Associated Appeals (UK Privy Council, Dec. 4 1967), LEVIE,
DOCUMENTS ON POWS 737, 741 (quoting LAUTERPACHT, II OPPENHEIM’S INTERNATIONAL LAW) (“‘The privileges
of members of armed forces cannot be claimed by members of the armed forces of a belligerent who go over to the
forces of the enemy and are afterwards captured by the former. They may be, and always are, treated as criminals.
The same applies to traitorous subjects of a belligerent who, without having been members of his armed forces, fight
in the armed forces of the enemy. Even if they appear under the protection of a flag of truce, deserters and traitors
may be seized and punished.’ This edition was published in 1951 after Aug. 12, 1949, the date of the Geneva
Conventions, and in their lordships’ opinion correctly states the relevant law.”).
87 Refer to § 17.12 (Use of Captured or Surrendered Enemy Personnel in NIAC).
88 See, e.g., Hamdi v. Rumsfeld 542 U.S. 507, 519 (2004) (plurality) (“There is no bar to this Nation’s holding one
of its own citizens as an enemy combatant.”); Ex parte Quirin, 317 U.S. 1, 37 (1942) (“Citizenship in the United
States of an enemy belligerent does not relieve him from the consequences of a belligerency which is unlawful
because in violation of the law of war.”); In re Territo, 156 F. 2d 142, 145 (9th Cir. 1946) (rejecting the argument of
petitioner, an Italian army draftee, that he could not be subject to the liabilities of combatant status and detained
because he was a U.S. citizen).
89 For example, DEPARTMENT OF THE ARMY PAMPHLET 20-213, History of Prisoner Of War Utilization By The
United States Army, 1776-1945, 198 (Jun. 24, 1955) (“During the [Second World] war many soldiers of a state of
origin other than Germany were found in German uniform among German prisoners of war. Therefore when Allied
forces captured these prisoners they segregated them by nationalities. The individual PW was then interrogated by
representatives of his country’s government in exile. If acceptable to that government and if he was willing, the PW
was sent to Great Britain for service in an army unit of his national government. If the PW was rejected, he was
treated in all respects as a German prisoner of war.”).
90For example, Announcement Concerning Soviet Allegations on Allied Prisoners of War, May 3, 1945, 12
DEPARTMENT OF STATE BULLETIN 864 (May 6, 1945) (“In as much as the American Government has always
insisted that all wearers of the American uniform, whether American citizens or not, are, as American soldiers,
entitled to full protection of the [1929] Geneva convention and has so informed the enemy, these German prisoners
of war of apparent Soviet nationality claiming such protection are being held as German prisoners of war in order to
protect American soldiers in enemy hands.”).
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4.5 ARMED FORCES OF A STATE
Members of the armed forces of a State, including members of all groups that are part of
the armed forces of a State, but excluding certain medical and religious personnel,91 receive
combatant status (i.e., its rights, duties, and liabilities) by virtue of that membership.92 This
section addresses various classes of persons within the armed forces of a State.
4.5.1 Components of Armed Forces. The armed forces of a State may include a variety
of components, such as militia or volunteer corps that form part of those armed forces.93
The U.S. armed forces include members of the active duty military, the reserve forces,
and the National Guard. U.S. armed forces also include the Coast Guard, which normally
operates under the Department of Homeland Security.94
The U.S. armed forces may also include the Commissioned Corps of the U.S. Public
Health Service, which normally operates under the Department of Health and Human Services.95
Similarly, members of the Commissioned Corps of the National Oceanic and Atmospheric
Administration, which normally operates under the Department of Commerce, may also become
part of the U.S. armed forces.96 Members of these and other organizations assigned to, and
serving with, the U.S. armed forces may be subject to the Uniform Code of Military Justice.97
91 Refer to § 4.9 (Military Medical and Religious Personnel).
92 See GPW art. 4A(1) (defining “prisoners of war, in the sense of the present Convention,” to include “(1)
[m]embers of the armed forces of a Party to the conflict” who have fallen into the power of the enemy); HAGUE IV
REG. art. 1 (“The laws, rights, and duties of war apply … to armies”); LIEBER CODE art. 57 (“So soon as a man is
armed by a sovereign government and takes the soldier’s oath of fidelity, he is a belligerent;”). Cf. sources cited in
footnote 150 in § 4.6.1.3 (Application of GPW 4A(2) Conditions to the Armed Forces of a State).
93 See GPW art. 4A(1) (defining “prisoners of war, in the sense of the present Convention,” to include “members of
militias or volunteer corps forming part of such armed forces” who have fallen into the power of the enemy); HAGUE
IV REG. art. 1 (“In countries where militia or volunteer corps constitute the army, or form part of it, they are
included under the denomination ‘army.’”).
94 See 10 U.S.C. § 101(a)(4) (explaining that, for the purposes of U.S. domestic law, “the term ‘armed forces’ means
the Army, Navy, Air Force, Marine Corps, and Coast Guard.”); 14 U.S.C. § 1 (“The Coast Guard as established
January 28, 1915, shall be a military service and a branch of the armed forces of the United States at all times. The
Coast Guard shall be a service in the Department of Homeland Security, except when operating as a service in the
Navy.”).
95 42 U.S.C. § 217 (“In time of war, or of emergency involving the national defense proclaimed by the President, he
may by Executive order declare the commissioned corps of the [Public Health] Service to be a military service.”).
96 33 U.S.C. § 3061 (“The President may, whenever in the judgment of the President a sufficient national emergency
exists, transfer to the service and jurisdiction of a military department such vessels, equipment, stations, and officers
of the Administration as the President considers to be in the best interest of the country. … An officer of the
Administration transferred under this section, shall, while under the jurisdiction of a military department, have
proper military status and shall be subject to the laws, regulations, and orders for the government of the Army,
Navy, or Air Force, as the case may be, insofar as the same may be applicable to persons whose retention
permanently in the military service of the United States is not contemplated by law.”).
97 10 U.S.C. § 802(a)(8) (“Members of the National Oceanic and Atmospheric Administration, Public Health
Service, and other organizations, when assigned to and serving with the armed forces,” are subject to the Uniform
Code of Military Justice).
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The U.S. armed forces may also include the volunteer auxiliary of the Air Force when the
services of the Civil Air Patrol are used in certain missions.98
4.5.1.1 Reserve Armed Forces. Although domestic law sometimes differentiates
between the reserve and active components of the armed forces for the purpose of entitlement to
benefits and other matters, international law treats members of the reserve forces that are part of
the armed forces of a State the same as other members of the armed forces.
In the United States, reserve armed forces include the reserve components of the Army,
Navy, Air Force, Marine Corps, and Coast Guard, as well as the Army National Guard of the
United States and the Air National Guard of the United States.99
4.5.2 Classes of Persons Within the Armed Forces.
4.5.2.1 Special Operations Forces. Special operations forces may be described as
military forces specially organized, trained, and equipped to achieve military, political,
economic, and psychological objectives by unconventional military means in hostile, denied, or
politically sensitive areas.100 As members of the armed forces, special operations forces have the
same rights, duties, and liabilities as other members of the armed forces.101
Nonetheless, in the past, some States have illegitimately questioned whether special
operations forces are entitled to the privileges of combatant status. For example, during World
War II, Hitler directed that German forces summarily execute captured Allied special operations
forces.102 Post-World War II war crimes tribunals found that this order was not a legitimate
98 See 10 U.S.C. § 9442(b)(1) (“The Secretary of the Air Force may use the services of the Civil Air Patrol to fulfill
the noncombat programs and missions of the Department of the Air Force.”).
99 10 U.S.C. § 10101 (“The reserve components of the armed forces are: (1) The Army National Guard of the
United States. (2) The Army Reserve. (3) The Navy Reserve. (4) The Marine Corps Reserve. (5) The Air National
Guard of the United States. (6) The Air Force Reserve. (7) The Coast Guard Reserve.”).
100 JOINT PUBLICATION 3-05, Special Operations, ix (Jul. 16, 2014) (“Special operations require unique modes of
employment, tactics, techniques, procedures, and equipment. They are often conducted in hostile, denied, or
politically and/or diplomatically sensitive environments, and are characterized by one or more of the following:
time-sensitivity, clandestine or covert nature, low visibility, work with or through indigenous forces, greater
requirements for regional orientation and cultural expertise, and a higher degree of risk. Special operations provide
joint force commanders (JFCs) and chiefs of mission with discrete, precise, and scalable options that can be
synchronized with activities of other interagency partners to achieve United States Government (USG) objectives.”).
101 Refer to § 4.4 (Rights, Duties, and Liabilities of Combatants).
102 Adolf Hitler, Commando Order, reprinted in Trial of Generaloberst Nickolaus von Falkenhorst, XI U.N. LAW
REPORTS 18, 20-21 (British Military Court, Brunswick, Jul. 29-Aug. 2, 1946); also reprinted in United States v. von
Leeb, et al. (The High Command Case), XI TRIALS OF WAR CRIMINALS BEFORE THE NMT 525-27; also reprinted in
The Dostler Case, Trial of General Anton Dostler, I U.N. LAW REPORTS 22, 33-34 (U.S. Military Commission,
Rome, Oct. 8-12, 1945).
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