Military Necessity

In times of armed conflict, military necessity is the concept used to justify the use of armed force. The use of armed force is governed by international humanitarian law (IHL) also known as the law of armed conflict or the law of war. IHL governs the conduct of hostilities by limiting the means and methods of warfare to ensure that military necessity remains bound and balanced by another fundamental principle, that of humanity, also enshrined in IHL. The rules of IHL embody a thoughtful balance between the two fundamental principles of humanity and military necessity. This balance shall guide the interpretation of those rules (especially for the principles of distinction, precautions and proportionality). IHL rules are designed to limit suffering, death, injury and destruction in armed conflict, especially that which is not directly related to, or excessive in relation to, a specific military necessity and advantage given that in the midst of warfare, military operations inevitably cause harm.

Historically, one of the first national codifications of the military can be found in the Lieber Code adopted in 1863 to regulate the conduct of Union soldiers during the United State of America civil war. It allowed only the use of military force justified by “military necessity”, defined as such “measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war.” (art. 14 of the Lieber Code). Military necessity is limited by the principle of humanity. The Lieber Code therefore states in article 16 that: “Military necessity does not admit of cruelty —that is, the infliction of suffering for the sake of suffering or for revenge, nor of maiming or wounding except in fight, nor of torture to extort confessions. It does not admit of the use of poison in any way, nor of the wanton devastation of a district”. This historical precedent has inspired the military manuals of other countries and the subsequent codification of IHL.

The principle of military necessity requires that a party to an armed conflict may resort only to the means and methods that are necessary to achieve the legitimate aims of the armed conflict. As explained in the Handbook of Humanitarian Law in Armed Conflicts and also confirmed by the International Criminal Tribunal for the former Yugoslavia (ICTY) ( Prosecutor v. Blaškić , Case no. IT-95-14-T, Judgment , 3 March 2000, para. 157):

“The question of military necessity refers to rules of international humanitarian law and the principle that a belligerent may apply only that amount and kind of force necessary to defeat the enemy. The unnecessary or wanton application of force is therefore prohibited.”

As the Handbook explains, there is no international authoritative definition of military necessity, even when it stands as an exception to some IHL rules. However, the relevant literature and jurisprudence agrees on its basic components: military necessity is an action that is (1) urgent; (2) necessary to achieve of (3) a known military purpose; and (4) consistent with international humanitarian law.

Indeed, any violence or destruction that is not justified by military necessity is prohibited by IHL. The use of armed force is legitimate only in the pursuit of specific military objectives, and then only as it remains within the limits of the rule and principle of proportionality. Under the rule of proportionality, the military necessity is closely linked to the military advantage expected from an attack. This anticipated military advantage must be weighed against the expected civilians casualties and damage resulting from and preceding such an attack.

Conversely, the concept of military necessity can be used to challenge the use of armed force when it appears that the violence or destruction were:

•unnecessary —the target or victims were not linked to a specific military objective; •disproportionate —the military advantage was disproportionate to the collateral damage to civilians;

•indiscriminate —the attack did not distinguish between military targets and civilian objects; and

•aimed at spreading terror among the civilian population.

Military necessity can neither justify nor authorise acts prohibited by IHL. Derogating from a rule of IHL on the grounds of military necessity is possible only for those rules which expressly provide for it (ICRC, Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 , 1987, para. 1389 and Commentary on the Third Geneva Convention , 2020, para. 497). Military necessity function both as a fundamental principle and as an exception to primary rules of protection afforded by IHL. Indeed, military necessity can act as an exception provided that both conduct and purpose otherwise comply with the law. For example, some IHL protections for civilians and other protected persons can be limited by the imperative military necessity exception but only in cases where its admissibility is explicitly and deliberately provided for (see GCI, art. 33; GCII, art. 28; GCIII, art. 126; GCIV, arts. 108 and 143; API, arts. 54(5), 62(1), 67(4) and 71(3); CIHL, rules 43 and 50).

In instances where breaches of the Geneva Conventions are alleged to amount to war crimes and/or crimes against humanity, establishing the absence of any military necessity becomes a requirement for the prosecution and must be proven. A posteriori , a court may assess the justifiability of the military necessity of an attack on the basis of the following evidentiary standard enunciated by the ICTY: “Whether a military advantage can be achieved must be decided […] from the perspective of the ‘person contemplating the attack, including the information available to the latter, that the object is being used to make an effective contribution to military action.’ In other words, each case must be determined on its facts.” ( Prosecutor v. Strugar , Case no. IT-01-42-T, Judgment , 31 January 2005, para. 295; Prosecutor v. Galić , Case no. IT-98-29-T, Judgment , 5 December 2003, para. 51).

Military necessity does not stand in isolation from other rules and principles of IHL. It must always be articulated with rules relating to the means and methods of warfare, military objectives, attacks, proportionality and the protection of civilians. In other words, the assertion of military necessity is not sufficient to justify an attack, or any coercive action not expressly prohibited by IHL. Commentaries to the Additional protocols to the Geneva Conventions have clarified that the absence of an express prohibition in IHL for a particular military practice does not mean that it is permissible (ICRC, Commentary on the Additional Protocols of 8 June 1977 to the Geneva Conventions of 12 August 1949 , Article 35 of API, 1987, para. 1395 and Commentary on the Third Geneva Convention , 2020, para. 497).

This is particularly important to ensure that rapidly evolving military practices and weapons remains within the bounds of IHL. This is notably the case in a number of challenging situations, including cyber warfare, cluster munitions and urban warfare, targeted killing, etc.

It is also important to ensure respect of IHL in specific contexts of armed conflict, in particular wars against designated terrorist groups, where the argument of national security is used in addition to military necessity to invoke derogations from IHL and the rule of law.

The Nuremberg court notes that the principle of military necessity does not “justify a violation of positive rules”.

ICJ, Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), Judgement, 27 June 1986, para. 237:

Since the Court has found that the condition sine qua non required for the exercise of the right of collective self-defence by the United States is not fulfilled in this case, the appraisal of the United States activities in relation to the criteria of necessity and proportionality takes on a different significance. As a result of this conclusion of the Court, even if the United States activities in question had been carried on in strict compliance with the canons of necessity and proportionality, they would not thereby become lawful. If however they were not, this may constitute an additional ground of wrongfulness. On the question of necessity, the Court observes that the United States measures taken in December 1981 (or, at the earliest, March of that year - paragraph 93 above) cannot be said to correspond to a “necessity” justifying the United States action against Nicaragua on the basis of assistance given by Nicaragua to the armed opposition in El Salvador. First, these measures were only taken, and began to produce their effects. several months after the major offensive of the armed opposition against the Government of El Salvador had been completely repulsed (January 1981). and the actions of the opposition considerably reduced in consequence. Thus it was possible to eliminate the main danger to the Salvadorian Government without the United States embarking on activities in and against Nicaragua. Accordingly, it cannot be held that these activities were undertaken in the light of necessity. Whether or not the assistance to the contras might meet the criterion of proportionality, the Court cannot regard the United States activities summarized in paragraphs 80, 8 1 and 86, Le., those relating to the mining of the Nicaraguan ports and the attacks on ports, oil installations, etc., as satisfying that criterion. Whatever uncertainty may exist as to the exact scale of the aid received by the Salvadorian armed opposition from Nicaragua, it is clear that these latter United States activities in question could not have been proportionate to that aid. Finally on this point, the Court must also observe that the reaction of the United States in the context of what it reOrdering a displacement with the aim of ensuring the safety of the civilian population, such as in cases of epidemics or natural disasters, would not constitute a crime under Article 8(2)(e)(viii) of the Statute. For the concept of military necessity, the Chamber notes that the reference to ‘imperative military reasons’ (emphasis added) in the Statute, derived from Article 49 of the Fourth Geneva Convention, is not reproduced in the Elements of Crimes.garded as self-defence was continued long after the period in which any presumed armed attack by Nicaragua could reasonably be contemplated. (our emphasis)*

Ordering a displacement with the aim of ensuring the safety of the civilian population, such as in cases of epidemics or natural disasters, would not constitute a crime under Article 8(2)(e)(viii) of the Statute. For the concept of military necessity, the Chamber notes that the reference to ‘imperative military reasons’ (emphasis added) in the Statute, derived from Article 49 of the Fourth Geneva Convention, is not reproduced in the Elements of Crimes. In this regard, the Chamber recalls that it has defined the concept of military necessity with reference to the relevant provision in Article 14 of the Lieber Code, which describes military necessity as the need to take ‘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’. In light of this definition, and notably the reference to the ‘indispensable’ nature of the measures, the Chamber is of the view that the qualification ‘imperative’ is subsumed in the general concept of military necessity as defined by the Chamber. That notwithstanding, the Chamber considers that the explicit addition of the qualifier ‘imperative’ in the Statute aims to emphasise that the instances in which a lawful displacement may be ordered are limited. (our emphasis)

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The Prosecutor v. Germani Katanga, ICC-01/04-01/07, Judgment pursuant to article 74 of the Statute, 7 March 2014, para. 800:

“Article 8(2)(e)(i) of the Statute enshrines the prohibition on the direct targeting of civilians. The Chamber recalls that this prohibition can in no circumstances be counterbalanced by military necessity.” (our emphasis)

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And para. 894 reemphasises that the ICC uses the definition of military necessity from the Lieber Code.

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The Prosecutor v. Jean-Pierre Bemba Gombo, ICC-01/05-01/08, Judgment pursuant to Article 74 of the Statute, 21 March 2016, para. 123:

Trial Chamber II endorsed the definition of military necessity set out in Article 14 of the Lieber Code, which provides that “[m]ilitary 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”. (our emphasis)

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ECCC, Supreme Court Chamber, Appeal Judgement in Case 002/01, 23 November 2016, para 445:

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“[T]here is no indication that any of the killings relied upon by the Trial Chamber were committed lawfully or were justified by military necessity.”

ECCC, Case 002/01, Judgement, 7 August 2014, para. 450:

“Forced transfer involves the (i) intentional, (ii) forced displacement of individuals (iii) from an area in which they are lawfully present, (iv) not justified by concerns regarding the security of the civilian population or military necessity.”

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ECHR, Case of Kononov v. Latvia (Application no. 36376/04), Grand Chamber, Judgment, 17 May 2010, para. 127:

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As regards military necessity, the judgment [Wilhelm case at Nuremberg Trial] noted as follows:

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“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. In general, it 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, but it does not permit the killing of innocent inhabitants for purposes of revenge or the satisfaction of a lust to kill. The destruction of property to be lawful must be imperatively demanded by the necessities of war. Destruction as an end in itself is a violation of international law. There must be some reasonable connection between the destruction of property and the overcoming of the enemy forces.”

➔ Attacks </content/article/3/attacks/>__ ▸ Civilians </content/article/3/civilians/>__ ▸ Methods (and means) of warfare </content/article/3/methods-and-means-of-warfare/>__ ▸ Military objectives </content/article/3/military-objectives/>__ ▸ Proportionality </content/article/3/proportionality/>__ ▸ Protected objects and property </content/article/3/protected-objects-and-property/>__ ▸ Protected persons </content/article/3/protected-persons/>__ ▸ War </content/article/3/war/>__

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For Additional Information:*

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Bouvier, Antoine A., Sassòli, Marco,*How does law protect at war, Cases, Documents and Teaching Materials on Contemporary Practice in International Humanitarian Law (volumes I, II and III) , see the chapter on “Military necessity”, ICRC, 2012, 2580 pages. Available at https://casebook.icrc.org/a_to_z/glossary/military-necessity

Carnahan, Burrus M., “Lincoln, Lieber and the Laws of War: The Origins and Limits of the Principle of Military Necessity”,*American Journal of International Law , vol. 92, no. 213, April 1998, p. 213-231. Available at https://blogs.dickinson.edu/hist-282pinsker/files/2011/08/Carnahan.pdf

Dinstein, Yoram, T*he Conduct of Hostilities under the Law of International Armed Conflict , Cambridge: Cambridge University Press, 2004.

Draper, G. I. A. D., “Military Necessity and Humanitarian Imperatives.”,*Military Law and Law of War Review , RDMDG, vol. 12/2, 1973, p. 129-151.

Dworkin, Anthony, “Military Necessity and Due Process: The Place of Human Rights in the War on Terror.” In*New Wars, New Laws? , edited by David Wippman and Matthew Evangelista, 53-73. Ardsley, NY: Transnational, 2004.

Gardam, Judith,*Necessity, Proportionality and the Use of Force by States , Cambridge, CUP, 2004, 259 pages.

Greenwood, Christopher, “Historical Development and Legal Basis: in Dieter Fleck (ed.),*The Handbook of Humanitarian Law in Armed Conflicts , 4th edition, 25 February 2021, 816 pages (esp. paras. 130-132).

Hayashi, Nobuo, “Requirements of Military Necessity in International Humanitarian Law and International Criminal Law”,*Boston University International Law Journal , vol. 28, Issue 1, 2010, p. 39-140. Available at https://cdn.cloud.prio.org/files/b38f5faf-a904-4bb3-bebd 176865539d2b/Requirements%20of%20Military%20Necessity%20in%20International%20Humanitarian%20Law%20and%20International%20Criminal%20Law.pdf?inline=true

Henckaerts, Jean-Marie and Doswald-Beck, Louise.*Customary International Humanitarian Law, volume I: Rules , ICRC, 2005 (see rules 43 and 50). Available at https://ihl-databases.icrc.org/en/customary-ihl/v1/rule43 and https://ihl-databases.icrc.org/en/customary-ihl/v1/rule50

ICRC, Database,*Treaties, States Parties and Commentaries, Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977, Commentary of 01.01.1987 , Article 35 - Basic rules. Available at https://ihl-databases.icrc.org/en/ihl-treaties/api-1977/article-35/commentary/1987

Handbook on International Rules Governing Military Operations* , December 2013, 464 pages. Available at https://www.icrc.org/sites/default/files/topic/file_plus_list/0431-handbook_on_international_rules_governing_military_operations.pdf

The principles of humanity and necessity* , March 2023. Available at https://www.icrc.org/sites/default/files/wysiwyg/war-and-law/02_humanity_and_necessity-0.pdf

Jaworski, Eric, “Military Necessity and Civilian Immunity: Where Is the Balance?” In*International Crime and Punishment , Selected Issues, vol. 2, edited by Sienho Yee, 87-127. Lanham, MD: University Press of America, 2004.

MacCoubrey, Hilaire, “The Nature of the Modern Doctrine in Military Necessity”,*Military Law and Law of War Review , (1991): 251-252.

Melzer, Nils, “Targeted Killing or Less Harmful Means?, Israel’s High Court Judgment on Targeted Killing and the Restrictive Function of Military Necessity”, in*Yearbook of International Humanitarian Law (YIHL) , vol. 9, 2009, p. 87-116.

Mulinen, Frederic de.,*Handbook on the Law of War for Armed Forces, Geneva: ICRC, 1989, esp. p. 82-84.

Prokosch, Éric, “Arguments for Restricting Cluster Weapons: Humanitarian Protection Versus ‘Military Necessity’ ”,*International Review of the Red Cross , vol. 34, No. 299, March-April 1994, p. 183-193. Available at https://international-review.icrc.org/sites/default/files/S0020860400078347a.pdf

Ragone, P.A., “The Applicability of Military Necessity in the Nuclear Age”, in*N.Y.U. Journal of International Law and Politics , vol. 16/4, 1984, p. 701-714.

Schmidt, Michael N., “Military necessity and Humanity in International humanitarian law: Preserving a delicate Balance”; in*Virginia Journal of International Law , vol. 50, no. 4, 2010, p. 795-839. Available at https://www.onlinelibrary.iihl.org/wp-content/uploads/2021/07/Military-Necessity-Humanity-Balance.pdf