The First Geneva Convention governing the sick and wounded members of armed forces was signed in 1864.

The law of war is a component of international law that regulates the conditions for initiating war (jus ad bellum) and the conduct of hostilities (jus in bello). Laws of war define sovereignty and nationhood, states and territories, occupation, and other critical terms of law.

Among other issues, modern laws of war address the declarations of war, acceptance of surrender and the treatment of prisoners of war, military necessity, along with distinction and proportionality; and the prohibition of certain weapons that may cause unnecessary suffering.[1][2]

The law of war is considered distinct from other bodies of law—such as the domestic law of a particular belligerent to a conflict—which may provide additional legal limits to the conduct or justification of war.

Early sources and history

The first traces of a law of war come from the Babylonians. It is the Code of Hammurabi,[3] king of Babylon, which in 1750 B.C., explains its laws imposing a code of conduct in the event of war:

I prescribe these laws so that the strong do not oppress the weak.

In ancient India, the Mahabharata and the texts of Manou's law urged mercy on unarmed or wounded enemies. The Bible and the Qur'an also contain rules of respect for the adversary. It is always a matter of establishing rules that protect civilians and the defeated.

Attempts to define and regulate the conduct of individuals, nations, and other agents in war and to mitigate the worst effects of war have a long history. The earliest known instances are found in the Mahabharata and the Old Testament (Torah). In the Indian subcontinent, the Mahabharata describes a discussion between ruling brothers concerning what constitutes acceptable behavior on a battlefield, an early example of the rule of proportionality:[citation needed]

One should not attack chariots with cavalry; chariot warriors should attack chariots. One should not assail someone in distress, neither to scare him nor to defeat him ... War should be waged for the sake of conquest; one should not be enraged toward an enemy who is not trying to kill him.

An example from the Book of Deuteronomy 20:19–20 limits the amount of environmental damage, allowing only the cutting down of non-fruitful trees for use in the siege operation, while fruitful trees should be preserved for use as a food source.[citation needed] Similarly, Deuteronomy 21:10–14 requires that female captives who were forced to marry the victors of a war, then not desired anymore, be let go wherever they want, and requires them not to be treated as slaves nor be sold for money.[citation needed]

In the early 7th century, the first Sunni Muslim caliph, Abu Bakr, whilst instructing his Muslim army, laid down rules against the mutilation of corpses, killing children, females and the elderly. He also laid down rules against environmental harm to trees and slaying of the enemy's animals:

Stop, O people, that I may give you ten rules for your guidance in the battlefield. Do not commit treachery or deviate from the right path. You must not mutilate dead bodies. Neither kill a child, nor a woman, nor an aged man. Bring no harm to the trees, nor burn them with fire, especially those which are fruitful. Slay not any of the enemy's flock, save for your food. You are likely to pass by people who have devoted their lives to monastic services; leave them alone.[4][5]

In the history of the early Christian church, many Christian writers considered that Christians could not be soldiers or fight wars. Augustine of Hippo contradicted this and wrote about 'just war' doctrine, in which he explained the circumstances when war could or could not be morally justified.

In 697, Adomnan of Iona gathered Kings and church leaders from around Ireland and Scotland to Birr, where he gave them the 'Law of the Innocents', which banned killing women and children in war, and the destruction of churches.[6]

Apart from chivalry in medieval Europe, the Roman Catholic Church also began promulgating teachings on just war, reflected to some extent in movements such as the Peace and Truce of God. The impulse to restrict the extent of warfare, and especially protect the lives and property of non-combatants continued with Hugo Grotius and his attempts to write laws of war.

Modern sources

See also: Sources of international law

The signing of the First Geneva Convention by some of the major European powers in 1864.

The modern law of war is made up from three principal sources:[1]

Positive international humanitarian law consists of treaties (international agreements) that directly affect the laws of war by binding consenting nations and achieving widespread consent.

The opposite of positive laws of war is customary laws of war,[1] many of which were explored at the Nuremberg War Trials. These laws define both the permissive rights of states as well as prohibitions on their conduct when dealing with irregular forces and non-signatories.

The Treaty of Armistice and Regularization of War signed on November 25 and 26, 1820 between the president of the Republic of Colombia, Simón Bolívar and the Chief of the Military Forces of the Spanish Kingdom, Pablo Morillo, is the precursor of the International Humanitarian Law.[7] The Treaty of Guadalupe Hidalgo, signed and ratified by the United States and Mexico in 1848, articulates rules for any future wars, including protection of civilians and treatment of prisoners of war.[8] The Lieber Code, promulgated by the Union during the American Civil War, was critical in the development of the laws of land warfare.[9]

Historian Geoffrey Best called the period from 1856 to 1909 the law of war's "epoch of highest repute."[10] The defining aspect of this period was the establishment, by states, of a positive legal or legislative foundation (i.e., written) superseding a regime based primarily on religion, chivalry, and customs.[11] It is during this "modern" era that the international conference became the forum for debate and agreement between states and the "multilateral treaty" served as the positive mechanism for codification.

The Nuremberg War Trial judgment on "The Law Relating to War Crimes and Crimes Against Humanity"[12] held, under the guidelines Nuremberg Principles, that treaties like the Hague Convention of 1907, having been widely accepted by "all civilised nations" for about half a century, were by then part of the customary laws of war and binding on all parties whether the party was a signatory to the specific treaty or not.

Interpretations of international humanitarian law change over time and this also affects the laws of war. For example, Carla Del Ponte, the chief prosecutor for the International Criminal Tribunal for the former Yugoslavia pointed out in 2001 that although there is no specific treaty ban on the use of depleted uranium projectiles, there is a developing scientific debate and concern expressed regarding the effect of the use of such projectiles and it is possible that, in future, there may be a consensus view in international legal circles that use of such projectiles violates general principles of the law applicable to use of weapons in armed conflict.[13] This is because in the future it may be the consensus view that depleted uranium projectiles breach one or more of the following treaties: The Universal Declaration of Human Rights, the Charter of the United Nations, the Genocide Convention, the United Nations Convention Against Torture, the Geneva Conventions including Protocol I, the Convention on Conventional Weapons of 1980, the Chemical Weapons Convention, and the Convention on the Physical Protection of Nuclear Material.[14]

Purposes of the laws

It has often been commented that creating laws for something as inherently lawless as war seems like a lesson in absurdity. But based on the adherence to what amounted to customary international humanitarian law by warring parties through the ages, it was believed by many, especially after the eighteenth century, that codifying laws of war would be beneficial.[15]

Some of the central principles underlying laws of war are:[citation needed]

To this end, laws of war are intended to mitigate the hardships of war by:

The idea that there is a right to war concerns, on the one hand, the jus ad bellum, the right to make war or to enter war, assuming a motive such as to defend oneself from a threat or danger, presupposes a declaration of war that warns the adversary: war is a loyal act, and on the other hand, jus in bello, the law of war, the way of making war, which involves behaving as soldiers invested with a mission for which all violence is not allowed. In any case, the very idea of a right to war is based on an idea of war that can be defined as an armed conflict, limited in space, limited in time, and by its objectives. War begins with a declaration (of war), ends with a treaty (of peace) or surrender agreement, an act of sharing, etc.[16]

Principles of the laws of war

An 1904 article outlining the basic principles of the law of war, as published in the Tacoma Times.

Military necessity, along with distinction, proportionality, humanity (sometimes called unnecessary suffering), and honor (sometimes called chivalry) are the five most commonly cited principles of international humanitarian law governing the legal use of force in an armed conflict.

Military necessity is governed by several constraints: an attack or action must be intended to help in the defeat of the enemy; it must be an attack on a legitimate military objective,[17] and the harm caused to protected civilians or civilian property must be proportional and not excessive in relation to the concrete and direct military advantage anticipated.[18]

Distinction is a principle under international humanitarian law governing the legal use of force in an armed conflict, whereby belligerents must distinguish between combatants and protected civilians.[a][19]

Proportionality is a principle under international humanitarian law governing the legal use of force in an armed conflict, whereby belligerents must make sure that the harm caused to protected civilians or civilian property is not excessive in relation to the concrete and direct military advantage expected by an attack on a legitimate military objective.[18] However, as Robbie Sabel, Professor of international law at the Hebrew University, who has written on this topic, notes: “Anyone with experience in armed conflict knows that you want to hit the enemy’s forces harder than they hit you… if you are attacked with a rifle, there is no rule that stipulates that you can only shoot back with a rifle, but using a machine gun would not be fair, or that if you are attacked with only one tank you cannot shoot back with two.”[20]

Humanity is a principle based on the 1907 Hague Convention IV - The Laws and Customs of War on Land restrictions against using arms, projectiles, or materials calculated to cause suffering or injury manifestly disproportionate to the military advantage realized by the use of the weapon for legitimate military purposes. In some countries, weapons are reviewed prior to their use in combat to determine if they comply with the law of war and are not designed to cause unnecessary suffering when used in their intended manner. This principle also prohibits using an otherwise lawful weapon in a manner that causes unnecessary suffering.[21]

Honour is a principle that demands a certain amount of fairness and mutual respect between adversaries. Parties to a conflict must accept that their right to adopt means of injuring each other is not unlimited, they must refrain from taking advantage of the adversary's adherence to the law by falsely claiming the law's protections, and they must recognize that they are members of a common profession that fights not out of personal hostility but on behalf of their respective States.[21]

Example substantive laws of war

To fulfill the purposes noted above, the laws of war place substantive limits on the lawful exercise of a belligerent's power. Generally speaking, the laws require that belligerents refrain from employing violence that is not reasonably necessary for military purposes and that belligerents conduct hostilities with regard for the principles of humanity and chivalry.

However, because the laws of war are based on consensus (as the nature of international law often relies on self-policing by individual states), the content and interpretation of such laws are extensive, contested, and ever-changing.[22]

The following are particular examples of some of the substance of the laws of war, as those laws are interpreted today.

Declaration of war

Main article: Declaration of war

Section III of the Hague Convention of 1907 required hostilities to be preceded by a reasoned declaration of war or by an ultimatum with a conditional declaration of war.

Some treaties, notably the United Nations Charter (1945) Article 2,[23] and other articles in the Charter, seek to curtail the right of member states to declare war; as does the older Kellogg–Briand Pact of 1928 for those nations who ratified it.See certified true copy of the text of the treaty in League of Nations, Treaty Series, vol. 94, p. 57 (No. 2137).

Lawful conduct of belligerent actors

Modern laws of war regarding conduct during war (jus in bello), such as the 1949 Geneva Conventions, provide that it is unlawful for belligerents to engage in combat without meeting certain requirements. Article 4(a)(2) of the Geneva Convention relative to the Treatment of Prisoners of War recognizes Lawful Combatants by the following characteristics:

Impersonating enemy combatants by wearing the enemy's uniform is possibly allowed, however the issue is unsettled. Fighting in that uniform is unlawful perfidy, as is the taking of hostages.[25]

Combatants also must be commanded by a responsible officer. That is, a commander can be held liable in a court of law for the improper actions of their subordinates. There is an exception to this if the war came on so suddenly that there was no time to organize a resistance, e.g. as a result of a foreign occupation.[citation needed]

People parachuting from an aircraft in distress

Main article: Attacks on parachutists

Modern laws of war, specifically within Protocol I additional to the 1949 Geneva Conventions, prohibits attacking people parachuting from an aircraft in distress regardless of what territory they are over. Once they land in territory controlled by the enemy, they must be given an opportunity to surrender before being attacked unless it is apparent that they are engaging in a hostile act or attempting to escape. This prohibition does not apply to the dropping of airborne troops, special forces, commandos, spies, saboteurs, liaison officers, and intelligence agents. Thus, such personnel descending by parachutes are legitimate targets and, therefore, may be attacked, even if their aircraft is in distress.

Red Cross, Red Crescent, Magen David Adom, and the white flag

The emblem of the International Committee of the Red Cross (French: Comité international de la croix-rouge).

Modern laws of war, such as the 1949 Geneva Conventions, also include prohibitions on attacking doctors, ambulances or hospital ships displaying a Red Cross, a Red Crescent, Magen David Adom, Red Crystal, or other emblem related to the International Red Cross and Red Crescent Movement. It is also prohibited to fire at a person or vehicle bearing a white flag, since that indicates an intent to surrender or a desire to communicate.[26]

In either case, people protected by the Red Cross/Crescent/Star or white flag are expected to maintain neutrality, and may not engage in warlike acts. In fact, engaging in war activities under a protected symbol is itself a violation of the laws of war known as perfidy. Failure to follow these requirements can result in the loss of protected status and make the individual violating the requirements a lawful target.[26]

Applicability to states and individuals

The law of war is binding not only upon states as such but also upon individuals and, in particular, the members of their armed forces. Parties are bound by the laws of war to the extent that such compliance does not interfere with achieving legitimate military goals. For example, they are obliged to make every effort to avoid damaging people and property not involved in combat or the war effort, but they are not guilty of a war crime if a bomb mistakenly or incidentally hits a residential area.[citation needed]

By the same token, combatants that intentionally use protected people or property as human shields or camouflage are guilty of violations of the laws of war and are responsible for damage to those that should be protected.[26]


The use of contracted combatants in warfare has been an especially tricky situation for the laws of war. Some scholars claim that private security contractors appear so similar to state forces that it is unclear if acts of war are taking place by private or public agents.[27] International law has yet to come to a consensus on this issue.

See also: Convention on Mercenaries

Remedies for violations

During conflict, punishment for violating the laws of war may consist of a specific, deliberate and limited violation of the laws of war in reprisal.[citation needed]

After a conflict ends, persons who have committed or ordered any breach of the laws of war, especially atrocities, may be held individually accountable for war crimes. Also, nations that signed the Geneva Conventions are required to search for, try and punish, anyone who had committed or ordered certain "grave breaches" of the laws of war. (Third Geneva Convention, Article 129 and Article 130.)

Combatants who break specific provisions of the laws of war are termed unlawful combatants. Unlawful combatants who have been captured may lose the status and protections that would otherwise be afforded to them as prisoners of war, but only after a "competent tribunal" has determined that they are not eligible for POW status (e.g., Third Geneva Convention, Article 5.) At that point, an unlawful combatant may be interrogated, tried, imprisoned, and even executed for their violation of the laws of war pursuant to the domestic law of their captor, but they are still entitled to certain additional protections, including that they be "treated with humanity and, in case of trial, shall not be deprived of the rights of fair and regular trial." (Fourth Geneva Convention Article 5.)

International treaties on the laws of war

See also: List of international declarations

List of declarations, conventions, treaties, and judgments on the laws of war:[28][29][30]

See also


  1. ^ Protected civilian in this instance means civilians who are enemy nationals or neutral citizens whose presence is outside the territory of a belligerent nation. Article 51.3 of Protocol I to the Geneva Conventions explains that "Civilians shall enjoy the protection afforded by this section, unless and for such time as they take a direct part in hostilities".



  1. ^ a b c d "What is IHL?" (PDF). 2013-12-30. Archived (PDF) from the original on 2013-12-30. Retrieved 2019-11-11.
  2. ^ United States; Department of Defense; Office of General Counsel (2016). Department of Defense law of war manual. OCLC 1045636386.
  3. ^ "1999-01". Archived from the original on 2006-03-09. Retrieved 2023-10-22.
  4. ^ Al-Muwatta; Book 21, Number 21.3.10.
  5. ^ Aboul-Enein, H. Yousuf and Zuhur, Sherifa, Islamic Rulings on Warfare, p. 22, Strategic Studies Institute, US Army War College, Diane Publishing Co., Darby PA, ISBN 1-4289-1039-5
  6. ^ Adomnan of Iona. Life of St. Columba, Penguin Books, 1995.
  7. ^ "Publicaciones Defensa". Publicaciones Defensa. Retrieved 2019-03-07.
  8. ^ "Avalon Project - Treaty of Guadalupe Hidalgo; February 2, 1848". Retrieved 2019-03-07.
  9. ^ See, e.g., Doty, Grant R. (1998). "THE UNITED STATES AND THE DEVELOPMENT OF THE LAWS OF LAND WARFARE" (PDF). Military Law Review. 156: 224.
  11. ^ 2 L. OPPENHEIM, INTERNATIONAL LAW §§ 67–69 (H. Lauterpacht ed., 7th ed. 1952).
  12. ^ Judgement : The Law Relating to War Crimes and Crimes Against Humanity Archived 2016-09-08 at the Wayback Machine contained in the Avalon Project archive at Yale Law School.
  13. ^ "The Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia: Use of Depleted Uranium Projectiles". 2007-03-05. Retrieved 2013-07-06.
  14. ^ E/CN.4/Sub.2/2002/38 Human rights and weapons of mass destruction, or with indiscriminate effect, or of a nature to cause superfluous injury or unnecessary suffering (backup).
  15. ^ Dunant, Henry; Dunant, Henry; Dunant, Henry (1986). A Memory of Solferino (Repr ed.). Geneva: International Committee of the Red Cross. ISBN 978-2-88145-006-8.
  16. ^ Stahn, C. (2006-11-01). "'Jus ad bellum', 'jus in bello' . . . 'jus post bellum'? -Rethinking the Conception of the Law of Armed Force". European Journal of International Law. 17 (5): 921–943. doi:10.1093/ejil/chl037. ISSN 0938-5428.
  17. ^ Article 52 of Additional Protocol I to the Geneva Conventions provides a widely accepted definition of military objective: "In so far as objects are concerned, military objectives are limited to those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage." (Source: Moreno-Ocampo 2006, page 5, footnote 11).
  18. ^ a b Moreno-Ocampo 2006, See section "Allegations concerning War Crimes" Pages 4,5.
  19. ^ Greenberg 2011, Illegal Targeting of Civilians.
  20. ^ Sabel, Robbie (December 18, 2023). "International Law and the Conflict in Gaza". Israel Journal of Foreign Affairs. 17 (3): 4.
  21. ^ a b "Basic Principles of the Law Of War and Their Targeting Implications" (PDF). Curtis E. LeMay Center. US Air Force. Public Domain This article incorporates text from this source, which is in the public domain.
  22. ^ Jefferson D. Reynolds. "Collateral Damage on the 21st century battlefield: Enemy exploitation of the law of armed conflict, and the struggle for a moral high ground". Air Force Law Review Volume 56, 2005(PDF) Page 57/58 "if international law is not enforced, persistent violations can conceivably be adopted as customary practice, permitting conduct that was once prohibited"
  23. ^ "Charter of the United Nations, Chapter 1". United Nations. Retrieved 13 February 2020.
  24. ^ "Geneva Convention relative to the Treatment of Prisoners of War, 75 U.N.T.S. 135". University of Minnesota Human Rights Library. United Nations. 1950-09-21. Retrieved 2021-09-12.
  25. ^ "Rule 62. Improper Use of the Flags or Military Emblems, Insignia or Uniforms of the Adversary". Retrieved 2023-08-30. However, their employment is forbidden during a combat, that is, the opening of fire whilst in the guise of the enemy. But there is no unanimity as to whether the uniform of the enemy may be worn and his flag displayed for the purpose of approach or withdrawal.
  26. ^ a b c Forsythe, David (2019-06-26), "International Committee of the Red Cross", International Law, Oxford University Press, doi:10.1093/obo/9780199796953-0183, ISBN 978-0-19-979695-3, retrieved 2023-06-09.
  27. ^ Phelps, Martha Lizabeth (December 2014). "Doppelgangers of the State: Private Security and Transferable Legitimacy". Politics & Policy. 42 (6): 824–849. doi:10.1111/polp.12100.
  28. ^ Roberts & Guelff 2000.
  29. ^ ICRC Treaties & Documents by date.
  30. ^ Phillips, Joan T. (May 2006). "List of documents and web links relating to the law of armed conflict in air and space operations". Alabama: Bibliographer, Muir S. Fairchild Research Information Center Maxwell (United States) Air Force Base.
  31. ^ "Treaties, States parties, and Commentaries - Geneva Convention, 1864".
  32. ^ "The project of an International Declaration concerning the Laws and Customs of War". Brussels. 27 August 1874 – via
  33. ^ "Brussels Conference of 1874 – International Declaration Concerning Laws and Customs of War". Stockholm International Peace Research Institute Project on Chemical and Biological Warfare. Archived from the original on 2007-07-11.
  34. ^ a b Brussels Conference of 1874 ICRC cites D. Schindler and J. Toman, The Laws of Armed Conflicts, Martinus Nihjoff Publisher, 1988, pp. 22–34.
  35. ^ The Hague Rules of Air Warfare, 1922–12 to 1923–02, this convention was never adopted (backup site).
  36. ^ Protocol for the Prohibition of the Use of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare. Geneva, 17 June 1925.
  37. ^ "Draft Convention for the Protection of Civilian Populations Against New Engines of War". Amsterdam – via The meetings of forum were from 29.08.1938 until 02.09.1938 in Amsterdam.
  38. ^ "Protection of Civilian Populations Against Bombing From the Air in Case of War". Unanimous resolution of the League of Nations Assembly. 30 September 1938.
  39. ^ "International Committee of the Red Cross". International Committee of the Red Cross. 3 October 2013.
  40. ^ Doswald-Beck, Louise (31 December 1995). "San Remo Manual on International Law Applicable to Armed Conflict at Sea". International Review of the Red Cross. pp. 583–594 – via
  41. ^ "Guidelines for Military Manuals and Instructions on the Protection of the Environment in Times of Armed Conflict". International Review of the Red Cross. 30 April 1996. pp. 230–237 – via
  42. ^ "Convention on the Safety of United Nations and Associated Personnel". 1995-12-31. Retrieved 2013-07-06.

General sources

Further reading