laws of war

The laws of war are rules governing the conduct of armed conflict and the protection of victims of war. They have also sometimes been called in the post-1945 period ‘international law of armed conflict’ or ‘international humanitarian law’. The classical name of the laws of war, often still used today, is jus in bello. This body of law is distinct from the rules governing the resort to armed conflict (jus ad bellum). The laws of war have for centuries encompassed a wide range of matters, including rights and duties of neutrals, treatment of POWs and of those wounded in battle, administration of occupied territories, negotiation and implementation of truces, limitations on means and methods of warfare, and war crimes.

The idea that the conduct of armed hostilities is governed by rules can be found in almost all societies. The Greeks and Romans customarily observed certain humanitarian principles. The Christian tradition placed emphasis on restraints on the conduct of war within the context of just-war theology in the works of such writers as St Augustine of Hippo (354-430) and St Thomas Aquinas (1226-74). In the Middle Ages, a law of arms was developed in Europe to govern discipline within armies as well as to regulate the conduct of hostilities. From the 15th century onwards, early European writers on international law such as Legnano, Victoria, Gentili, and Grotius wrote extensively on the laws of war. Ideas of restraint in the use of force also had a place in poetry and drama.

For centuries, the customary rules regarding the conduct of armed hostilities have been enunciated not only in the writings of individuals, but also in official statements of various kinds, including in military codes. From at least the early 17th century neutrality in war, especially at sea, was frequently addressed in bilateral treaties. The paradox that one of the first areas of international law to be developed was that which concerned war is partly explained by the fact that peaceful relations can often be regulated on an ad hoc basis, whereas wars repeatedly pose questions of a general character which cannot be settled at the time by agreement between adversaries, and therefore need to be addressed earlier.

In the second half of the 19th century the idea of the multilateral treaty, open to any state to accept, became the main focus of international law-making. The laws of war had a pioneering part in this process. The 1856 Paris Declaration on Maritime Law, which (at the conclusion of the Crimean war) laid down general rules on relations between belligerent and neutral shipping in wartime, has a strong claim to be regarded as the first modern multilateral treaty. In 1864 the first of what was to be a long stream of Geneva Conventions was concluded, for the ‘Amelioration of the Condition of the Wounded in Armies in the Field’. This spelt out the principle that those helping the wounded, on or off the battlefield, were to be recognized as neutral and to be protected from attack. The Red Cross was to be used as a symbol of humanitarian work and a guarantee of immunity.

A classic statement of the purposes of the laws of war as seen at this time was in the 1868 St Petersburg Declaration prohibiting explosive bullets. This said that ‘the only legitimate object which States should endeavour to accomplish during war is to weaken the military forces of the enemy’. This statement conveys a vision of war as a struggle between the uniformed armies of states, rather than between governments or peoples.

The laws of war were further developed at international conferences at The Hague in 1899 and 1907, particularly in the 1907 Hague Convention IV ‘Respecting the Laws and Customs of War on Land’ and annexed regulations, covering such matters as treatment of POWs, protection of hospitals, truce negotiations, and the conduct of armies in occupied territories. These rules, based on a justified fear that the 20th century would be one of total war, remain formally in force a century after they were drawn up.

WW I cast a shadow over this process of law-making. The many violations of the law had exposed its fragility, and the propaganda war about atrocities had shown how law could exacerbate mutual hostility. More fundamentally, much of the slaughter in trench warfare had been technically in accord with the Hague Regulations, exposing law as an inadequate means of limiting war. At the end of the war, governments were not much interested in further refining the jus in bello, but sought rather to prevent war altogether.

In the inter-war years, there was some further codification of the international law of armed conflict. Apart from agreements on the treatment of prisoners and of those wounded in war, the most important development was the 1925 Geneva Protocol prohibiting the use of chemical and biological weapons. This treaty, a rare example of a reasonably successful prohibition of use of a particular class of weapon, played some part in limiting the resort to these weapons in major international conflicts, including WW II. Its effectiveness is partly due to threats of retaliation in kind: many states, on becoming parties to the Protocol, declared that it would cease to be binding in relation to any enemy state which failed to respect it.

In WW II, many of the principles of the laws of war were violated, especially by the bombing of cities, the ruthless treatment of many POWs, and the massacres of Jews, gypsies, and others in Axis-occupied territories. The International Military Tribunals at Nuremberg and Tokyo immediately after the war, and many other courts as well, sought to punish leading Axis figures involved. Allied war practices went largely unexamined. This contrast fuelled the argument that the war crimes trials delivered ‘victor's justice’.

In the immediate aftermath of WW II there were hopes that, since the resort to force was severely restricted under the UN Charter, there would be no need for substantial further development of the jus in bello. However, a succession of wars in subsequent decades impressed on governments the need to update the law. At least twelve major treaties on the laws of war have been concluded since 1945. (Numbers of states parties as at 12 August 1999 are indicated in brackets):

• 1948	UN Genocide Convention (129).
• 1949	The four 1949 Geneva Conventions (188). These seek to protect four categories of victims under the power of the enemy: wounded and sick on land; wounded, sick, and shipwrecked at sea; POWs; and civilians.
• 1954	Hague Cultural Property Convention (95). Two protocols, concluded in 1954 and 1999, address the export of cultural property from occupied territory, and measures to improve implementation of the convention's provisions in civil as well as international wars.
• 1976	UN Convention on the Prohibition of Military Use of Environmental Modification Techniques (65).
• 1977	Protocol I Additional to the 1949 Conventions, and Relating to the Protection of Victims of International Armed Conflicts (155).
• 1977	Protocol II Additional to the 1949 Conventions, and Relating to the Protection of Victims of Non-international Armed Conflicts (148).
• 1980	UN Convention on Prohibitions or Restrictions of the Use of Certain Conventional Weapons (73). The Protocols annexed to the Convention (including two adopted in 1995 and 1996) address non-detectable fragments, landmines, incendiary weapons, and blinding laser weapons.
• 1997	Ottawa Convention Prohibiting the Use, Stockpiling, Production, and Transfer of Anti-Personnel Mines (84).
• 1998	Rome Statute of the International Criminal Court (4). Articles 5 to 8 contain an important summary of the crimes of genocide, crimes against humanity, and war crimes.

None of these agreements mentions the term nuclear weapons. The question of whether the threat and use of these could ever be compatible with the laws of war was addressed directly in an Advisory Opinion of the International Court of Justice on 8 July 1996. All fourteen judges agreed that the laws of war were applicable to nuclear as well as to other weapons, but not on the consequences that flowed from that proposition. All fourteen wrote separate statements, illustrating the difficulty of reaching a consensus view on this question.

So far as actual wars are concerned, the application of the laws of war does not depend upon the recognition of the existence of a formal state of ‘war’. Many treaties concluded since WW II refer to ‘armed conflict’ rather than ‘war’. The laws of war are applicable to all international wars, but there has been a problem regarding civil wars.

The extent to which the laws of war apply to civil wars has long been a matter of varied opinion and practice. Historically, governments have often been reluctant to treat rebels as legitimate belligerents entitled, for example, to POW status; and treaties on the laws of war have generally specified that they apply to international wars, without mentioning civil wars. However, certain rules are applicable in civil wars, including the prohibition on genocide; Article 3 in each of the four 1949 Geneva Conventions, which specifies some minimal rules to be applied in civil wars; and the 1977 Geneva Protocol II. In the 1990s, in response to the carnage of civil wars, there was further pressure to place legal limits on the actions of belligerents in civil wars. Both the 1997 Ottawa convention on landmines and the 1998 Rome Statute of the International Criminal Court, contain extensive provisions applicable in civil wars.

The case for applying the laws of war to internal armed conflicts has been strengthened by the fact that a high proportion of the wars of the 20th century, and especially of the post-1945 period, were internationalized civil wars, in which local belligerents gained the support of outside powers. In such cases, the simultaneous application of two sets of rules, for civil and international wars, poses problems. Some armed forces as a matter of policy train their troops to follow the rules for international armed conflict in all circumstances.

In general, the rules appear to work best when there is some degree of understanding and respect between belligerents. The rules regarding treatment of prisoners and others in the hands of the adversary have sometimes operated more effectively than the rules relating to the conduct of hostilities. In the conflicts of the post-1945 era implementation has been uneven. Often one side was unwilling to admit the legitimacy of the adversary's existence or status as a belligerent. Especially in civil wars, the distinction between the soldier and the civilian, basic to the modern laws of war, was not nearly as clear in practice as in theory. Extreme nationalism and ideological zeal militated against observing rules of moderation. Some violations of basic rules went unpunished.

Yet many limits were observed. In most wars, military prisoners received reasonable treatment. In the 1982 Falklands war, and the 1991 Gulf war, there was much (though not complete) observance of the rules. Such observance did not hamper, and may have positively assisted, the efficient professional conduct of operations.

In the 1990s, in the face of repeated and major violations of the laws of war, attempts were made to improve implementation. The UN Security Council's decision to establish the International Criminal Tribunal for the former Yugoslavia in 1993, and that for Rwanda in 1994, illustrated the trend, but the experience of the two tribunals also exposed some of the difficulties of trying to apply the law supranationally. In particular, the number of cases they dealt with in the first five years of their existence was very small when compared with the scope of the problems addressed. In 1998, a UN-convened conference in Rome adopted a treaty for the establishment of an International Criminal Court: 60 states must become parties before it enters into force. While international implementation is beginning, states and armed forces, with all their virtues and defects in this regard, remain the main mechanism for implementation and enforcement of the laws of war.

Bibliography

• Best, Geoffrey, Humanity in Warfare: The Modern History of the International Law of Armed Conflicts (London, 1980).
• —— War and Law since 1945 (Oxford, 1994).
• Howard, Michael, Andreopoulos, George J., and Shulman, Mark R. (eds.), The Laws of War: Constraints on Warfare in the Western World (New Haven, 1994).
• Keen, Maurice, The Laws of War in the Late Middle Ages (London, 1965).
• Roberts, Adam, and Guelff, Richard (eds.), Documents on the Laws of War (3rd edn., Oxford, 2000)

— Adam Roberts

The idea of laws of war is ancient and ubiquitous; fragmentary indications appear in the records of most known civilizations and cultures. The inter national laws of war as known today, however, are of relatively modern and regional origin. The Roman concept of a law of nations (jus gentium), persisting through Europe's medieval centuries and ingesting elements of Christian “just war” doctrine, chivalric honor, military professionalism, and commercial prudence, produced by the sixteenth century a body of customary principles and rules purporting to show how to judge whether a war was justified (jus ad bellum) and how wars should ideally be conducted (jus in bello). Reality, always falling short of the ideal, became so horrific in the Thirty Years' War that the Dutch Christian‐humanist‐diplomat Hugo Grotius (1583–1645) was prompted to publish in 1625 De jure belli ac pacis (Concerning the Law of War and Peace), usually considered the first definitive text on international law. Accepting war as a legitimate political institution, he maintained the just war thesis that it should not be begun without good cause, and argued with moral fervor that war could, indeed should, be conducted with more moderation than was usually the case. When, in the later nineteenth century, modern international law crystallized and the customary laws of war began to be codified, Grotius's visions of international community and universal standards renewed the respect for him that persists today.

The temporary eclipse of jus ad bellum did not mean that jus in bello was neglected. Men of honor took it seriously. Self‐respecting commanders of opposing forces made local agreements (“conventions”) to facilitate exchanges of prisoners and protect medical units. Recurrent disputes about particular incidents testified to the persistence of the ideas that there must be standards for governing the conduct of military operations, and that civilized states should wish their armed forces to observe them. So demanding had these ideas become by mid‐nineteenth century that they issued in four epochmaking and trail‐blazing events: the Paris Declaration of 1856, regulating the relations of belligerents and neutrals in maritime war; the Geneva Conventions of 1864; General Order No. 100 of the U. S. Army of 1864, Instructions for the Government of [Its] Armies in the Field—often known, after its principal author, as “the Lieber code”; and the St. Petersburg Declaration of 1868, a prohibition of an “atrocious” new weapon (explosive bullets).

From those close‐bunched beginnings, the laws of war developed along two main lines. “Geneva law” aimed to protect victims and innocents: the 1929 revision added to the existing conventions (for sick and wounded combatants on land and sea), a third regarding prisoners of war; in 1949, a fourth aimed to protect civilians who fell into enemy hands at the outbreak of hostilities or because of military occupation. The other line, law regarding the conduct of hostilities, of which Francis Lieber's code was for long the most famous and complete national example, became known as “Hague law” after the international standard setting in 1899 (reaffirmed by the Fourth Hague Convention of 1907) of the Hague Regulations Respecting the Laws and Customs of War on Land. Supplemented since 1977 by the First Protocol Additional to the Geneva Conventions (in fact, a convergence of Geneva and Hague law, to which most states by now have acceded), the Hague Regulations have ever been, and still are, fundamental to the laws of land war. Along with the Geneva Conventions, they formed the basis for the war crimes trials after World War II; most of which had to do with the behavior of armed forces in (contested) occupation of alien territories, and with the treatment of prisoners.

Standards for the conduct of war by air and sea have not been so easily reached. In these fields especially, military applications of science and technology have posed problems defying simple solution. New inventions promising military advantage have often at first been denounced as dishonorable or inhumane, but a few have ultimately been added to the list of weapons (e.g., chemical and biological weapons) covered by multilateral treaty prohibitions (1925 and 1972, respectively). It remains to be seen how effective will be the 1981 prohibitions or restrictions on the use of certain conventional weapons (mainly land mines, boobytraps, and incendiary weapons). Efforts were made between 1919 and 1939 to restrict submarine and aerial warfare, but they proved useless during World War II. Submarines were so vulnerable on the surface that, having to stay submerged, they could not observe the classic distinction between civilian and military; together with mines, they revolutionized war at sea by making possible blockades more total than ever before. Bombers dared not fly so low or slow that they could guarantee to hit only military objectives; at the same time, the passions of prolonged total war tended to encourage the indiscriminate and terroristic bombing of civilians. Both sides having waged air and sea war in these extreme and disproportionate ways, they figured hardly at all in the Nuremberg and Tokyo International Military Tribunals and the many nationally run war crimes trials. Not until 1977 were these specific problems addressed. Among the more valuable achievements of the First Additional Protocol is civilian‐protecting definition of military objectives, and, associated with it, rules of proportionality aimed at reducing to the realistic minimum the incidental risks to nonmilitary persons and places.

The laws of war are incapable of perfect observance. Beyond the fact that law like all other elements of war is subject to the erosions of confusion, error, and chance, observance is likely to be highest when states wish a war to remain limited, when neutrals are critically watchful, and when well‐disciplined armed forces fight one another in a relatively civilian‐free environment. The “desert war” in North Africa (1940–43), and the brief Falklands War in the South Atlantic between Britain and Argentina (1982) are exceptional. Circumstances are rarely so favorable. Wars between states are more likely to be all‐out than limited; nor are they often simply between states. The laws of war make some room for “noninternational armed conflict,” but nonstate parties may not wish or be able to conduct hostilities in a style consistent with the law, while states combating them may not like to regard them as if they were lawful belligerents. Civilians tend to be difficult to distinguish from combatants in guerrilla warfare, or revolutionary and people's wars; in such situations, all parties are tempted to turn to terror. And through it all runs the problem that has forever dogged the laws of war, and whose handling reveals the quality of the culture and the politics of which the warrior is the armed representative: how to distinguish what may be militarily necessary from what is merely convenient, and how to judge when enough violence is enough. Important to all, the laws of war are not a matter of concern solely to the military.

[See also Geneva Protocol on Chemical Warfare; Hague Peace Conferences: Just War Theory; War: Nature of War; War Crimes.]

Bibliography

• Oppenheim's International Law, Vol. 2: Disputes, War and Neutrality, 1905; 7th ed., ed. Hersch Lauterpacht, 1952.
• Daniel O'Connell, The Influence of Law on Sea Power, 1975.
• David Forsythe, Humanitarian Politics: The International Committee of the Red Cross, 1977.
• Philip R. Piccigallo, The Japanese on Trial. Allied War Crimes Operations in the East, 1945–1951, 1979.
• Adam Roberts and Richard Guelff, eds., Documents on the Laws of War, 1982; 2nd ed. 1989.
• W. Hays Parks, Air Law and the Law of War, Air Force Law Review, vol. 32, no. 1 (1990), pp. 1–225.
• Telford Taylor, The Anatomy of the Nuremberg Trials, 1993.
• Geoffrey Best, War and Law Since 1945, 1994.
• Michael Howard, George J. Andreopoulos, and Mark R. Shulman, eds., The Laws of War: Constraints on Warfare in the Western World, 1994

International rules and conventions that limit belligerents' action.

See the Introduction, Abbreviations and Pronunciation for further details.

The laws of war are the rules of international law that govern the conduct of war between nation-states, and are especially concerned with whether a use of force is allowed, when a state of war exists, the weapons and conduct of war, and the treatment of opponents, prisoners, neutrals, and noncombatants. They apply to the United States through enactments by Congress, the president, the Department of Defense, and specific commanders—as well as through the ratification of treaties including the Charter of the United Nations, and through those obligations of international custom binding according to the U.S. Constitution.

Early Limits on War

There have been limits on the conduct of war throughout military history. These limits persist even though they are frequently violated, often without punishment. The degree to which a nation complies with them is the degree to which that nation is perceived as civilized, just as compliance on the part of a nation's military is what distinguishes it as professional. Furthermore, in the twentieth century, principles of state and personal responsibility have led to the possibility of effective criminal enforcement.

Ancient laws of war dealt mostly with immunity from combat and with the commencement of hostilities. By custom and treaties, the city-states of ancient Greece respected truces, armistices, peace treaties, alliances, flags of truce and the immunity of heralds, truces to bury the dead, surrender conditions, and the inviolability of victory monuments. The neutrality of religious temples, the Olympic games and, sometimes, third-party states were ordinarily respected. Conformity to these rules was thought necessary to be civilized, to obey the gods, and to justify similar treatment from opponents.

The Roman iustum bellum required that attacks could not be made unless there had been a prior declaration of war or unless prior demands had not been satisfied. Roman law did not, of course, limit conquest, although the treatment of conquered lands and people was closely regulated.

Religion and manners were the sole limits on medieval warfare. Both Christianity and Islam placed limits on treatment of their faithful in war that did not apply to heretics or infidels. Both cultures evolved forms of chivalry that constrained the forms of battle and the treatment of prisoners, although such rules were often beneficial only to those with high rank. Neither could enslave a captured enemy of the same religion. The Christian church evolved a doctrine of just war and doctrines protecting noncombatants from death in war. These doctrines were reflected in canon law but not in national legal systems, which tended to follow the view associated with Niccolò Machiavelli and Carl von Clausewitz, that war is justified as a rational instrument of national policy, even for the purpose of conquest. Various attempts were made by popes and kings to improve the treatment of civilians in surrendered towns and to limit the horrors of war by banning devious or inhumane weapons, such as the crossbow or, later, the bayonet. While these attempts yielded no means of enforcement, still, armies often followed some humanitarian customs of war for the ancient reason of ease to the army, particularly by limiting looting.

The Seventeenth Through Early Twentieth Centuries

The modern law of war was invented during the age of the English colonies in North America. During the Thirty Years' War (1618–1648), Dutch jurist and ambassador Hugo Grotius published On the Law of War and Peace, an extended and systematic argument that nations are bound by natural law to respect other nations, that they should only engage in wars justified by grounds that would be satisfactory as claims for legally cognizable harms, and that they must respect the rights of noncombatants. This argument gained much attention but slow acceptance.

During the American Revolution, the guiding principle was not a law of war but the customs of the armies and navies of Europe; however, these customs were often violated, as with the American habit of sharpshooting enemy officers. One custom that was honored was the execution of spies. The U.S. Army's Articles of War (1775) did, however, codify many customs, such as the requirements of uniforms and organization.

By the mid-nineteenth century, there was both more formal organization of the U.S. military and greater agreement about the rules. In the Mexican War, General Winfield Scott created military commissions to prosecute U.S. soldiers and Mexican civilians for violations of the rules of war.

The first codification of the law of war by the United States was General Order 100, issued at the direction of President Lincoln by General-in-Chief Henry Halleck, enacting the rules set forth in a report by Francis Lieber, a German-American law professor at Columbia College in New York. Entitled Instructions for the Government of Armies of the United States in the Field, it augmented the 1775 articles but went much further, setting humane standards for the handling and exchange of prisoners, the freeing of slaves, the treatment of people and property in occupied territory, and the treatment of opposing combatants. With the notable exception of Sherman's surprise bombardment of Atlanta, the union Army appears to have complied with Lieber's Code, and the Southern armies seem to have emulated it. The U.S. Supreme Court acknowledged it as federal law in Ex parte Vallandigham, 68 US 243 (1863).

Lieber's Code immediately influenced international law. Translated into German by Johann Bluntschli, it formed the basis of his Das Moderne Kriegsrecht (1866) and was reprinted whole in most international law texts for the next fifty years. Its terms and ideas influenced the European powers at the first Geneva Convention (1864) to agree to standards of treatment for wounded prisoners of war. International conferences at The Hague in 1899 and 1907 codified much of the Code regarding the definition of combatants and treatment of neutrals into the international laws of war.

The Crimean War, the U.S. Civil War, and the Franco-Prussian War all provoked codification of the laws of war. The Declaration of Paris of 1856 outlawed privateering, made naval warfare a matter for state professionals, and established clearer rules regarding blockades and the rights of neutral shippers. The Geneva Convention of 1864 drafted the first code for the treatment of the enemy's wounded. The 1868 Declaration of Saint Petersburg announced that the only legitimate use of war is to weaken an enemy's military, and it restricted the use of small explosive or incendiary projectiles. A convention at The Hague in 1899 rejected the use of expanding bullets and asphyxiating gasses.

While the great states of Europe negotiated and signed conventions, the United States was slow to do so, although it abided by these norms separately. Only during World War I did the U.S. agree to abide by the Declaration of Paris of 1856. The U.S. did not sign the convention of 1864, the declaration of St. Petersburg, the 1899 Hague Convention, or the first Geneva Convention. Even so, the Hague Conventions of 1899 and 1907 were both derived from Lieber's Instructions, which the United States reissued in 1898, and in 1914 the U.S. Army first compiled The Rules of Land Warfare, a handbook for soldiers in battle.

American interest in international regulation of law increased dramatically with the presidency of Theodore Roosevelt. In 1904 Roosevelt called a meeting under terms of the 1899 convention, seeking to codify and extend the earlier conventions. The resulting Second Hague Peace Conference ended in 1907 with fourteen treaties, setting forth standards for the commencement of hostilities, customs and duties of warfare on land and sea, and the standards of neutrality. The U.S. signed and ratified these conventions, making them the first significant international laws of war to be law in the U.S. through treaty. This was not the only method by which the laws of war became U.S. law, however, and in The Paquete Habana, 175 US 677 (1900), the U.S. Supreme Court had recognized that the customary international law of war was enacted into U.S. law by the Constitution.

World Wars I and II and Their Consequences

The horrors of World War I, including the widespread violation of earlier pacts, led interwar peace conferences toward attempts at the prevention of war and the limiting of inhumane tactics and weapons, but these efforts met with only moderate success. The 1923 Hague Convention, on the rules of aerial warfare, failed to achieve sufficient ratification to come into force. The Geneva Gas Protocol (1925) prohibited the use in war of asphyxiating, poisonous, or other gases and of bacteriological methods of warfare. The Geneva Conventions of 1929 detailed the treatment of prisoners of war and of the enemy sick and wounded. The Washington Disarmament Conference (1921–1922) and the Treaty of London of 1930 limited submarine warfare against noncombatant ships. Despite occasional breaches, it is notable that there was widespread compliance with these treaties in the subsequent world war.

The great exceptions to this tendency toward compliance were the peace treaties, commencing with the Bryan Treaties of 1913 and 1914, and the controversial Versailles Treaty of 1919, all of which promoted limits on the grounds for commencing war, including requirements for investigation, arbitration, and peaceful settlement of disputes. This process culminated in the Kellogg-Briand Pact of 1928.

Named for French foreign minister Aristide Briand and U.S. secretary of state Frank B. Kellogg, this initially bilateral treaty was eventually signed by nearly all of the nations then on earth, each renouncing war as an instrument of national policy and agreeing to settle all disputes by peaceful means. A surfeit of qualifications allowed wars in defense of the Covenant of the League of Nations, other military treaties, the Monroe Doctrine, and for self-defense. More damning, there was no mechanism for enforcement, and the treaty was ineffective as a prior restraint to aggression. It was, however, one of the key bases for trials after World War II on charges of waging aggressive war in violation of international law.

Even so, none of these instruments prevented the horrors of World War II. At the war's end, the allies established tribunals at Nuremberg and Tokyo to try defeated leaders, soldiers, and sailors accused of war crimes, mainly crimes against peace, which included the planning, initiating, and waging of wars of aggression in violation of international law; crimes against humanity, including exterminations, deportations, and genocide; war crimes on the battlefield; and conspiring to commit the criminal acts of the first three counts. Of twenty-four major German defendants, three were acquitted, four imprisoned from ten to twenty years, three imprisoned for life, and twelve sentenced to hang. (Two were not tried, one owing to suicide and one to physical incapacity.) Of twenty-five major defendants in Japan, two received prison terms, sixteen life imprisonment, and seven were sentenced to hang. Both tribunals adopted the "Nuremberg principle," which held the individual and not just the state liable for violations of the laws of war. This principle was soon a maxim of military training in most developed nations.

With the adoption of the United Nations Charter in 1945, almost all the nations of the world committed to the peaceful settlement of disputes and agreed to renounce war except in self-defense. Under the sponsorship of the United Nations, additional conventions have been adopted outlawing genocide and crimes against humanity; further limiting the use of weapons of mass destruction, such as nuclear and biological weapons, and of particular inhumanity, such as exploding bullets; and further refining standards for the treatment of prisoners and the wounded. The Geneva Conventions of 1949 refined duties to the wounded and sick on land, to the wounded, sick, and shipwrecked at sea, to prisoners of war, and to civilians. Conventions in 1954 and 1977 sought to protect property of great cultural significance and to end deliberate acts of war that harm the environment.

The Cold War and After

The Cold War between the U.S. and the Soviet Union, the Korean War, and the American war in Vietnam raised new questions about the nature and application of the laws of war. The laws of war traditionally applied only to conflicts between de jure states, and controversies arose over the legality of U.S. actions when war was not declared, as with U.S. involvement in Vietnam and Cambodia in the 1960s. The Vietnam War also led to debates over the legal definition of war as a civil war, guerrilla war, or national war; the applicability of the laws of war in the absence of a uniformed enemy; the adherence of the parties to the laws and conventions of war; and the tactics used by the belligerents, particularly the American use of carpet bombing and defoliants, which damaged noncombatant areas.

Blame in these disputes was not one-sided. The North Vietnamese and Vietcong used terrorism and refused to adhere to the 1949 Geneva Convention—they did not, for example, permit the International Red Cross to inspect prisoner-of-war camps.

Greater agreement on matters of international law and the law of war followed the end of the Cold War in the 1990s. With American support, the U.N. Security Council created the International Criminal Tribunal for the Former Yugoslavia in 1993 and the International Criminal Tribunal for Rwanda in 1994. Both tribunals applied the Nuremberg principle and actively investigated and convicted individuals, including former Yugoslav president Slobodan Milosevic, for violations of the Geneva Convention of 1949. They were charged to investigate and prosecute genocide, violations of the laws and customs of war, and crimes against humanity. The violation of the laws and customs of war included using poisonous weapons or other weapons calculated to cause unnecessary suffering; wanton destruction of civilian areas not justified by military necessity; attack or bombardment of undefended towns; seizing or harming buildings dedicated to religion, charity, or education, or to the arts and sciences, or historic monuments and works of art and science; and plundering public or private property.

At Rome in 1998 a U.N. conference opened for signature a treaty establishing an International Criminal Court, with global jurisdiction to try individuals whose governments are unwilling to try them when they have been accused of any of various "crimes against humanity"—the definitions of which are similar to those established by the Yugoslavia and Rwanda tribunals. To become effective the treaty needed the ratification of sixty states, a goal that was achieved in April 2002. The United States had signed in 2000, but withdrew its signature in 2002.

On 11 September 2001 an attack by a terrorist organization undirected by any state, but apparently sheltered by a theocratic de facto government in Afghanistan, destroyed the towers of the World Trade Center in New York, one of the largest office buildings in history and a center of the commercial world. The attack killed nearly three thousand people, mainly Americans but including people from many nations. The response of the United States and its allies was to demand surrender of the leaders of the attack, and, in the absence of satisfaction, to attack the armies of the Afghan government while seeking to arrest the terrorists. As much criminal enforcement as military action, this response further signaled a comprehensive change in the structure of the laws of war, which now include an element of the enforcement of international criminal law.

Bibliography

Best, Geoffrey. War and Law Since 1945. Oxford and New York: Clarendon, 1994.

Brownlie, Ian. International Law and the Use of Force by States. Oxford: Clarendon, 1963.

Holland, Thomas Erskine. The Laws of War on Land (Written and Unwritten). Oxford: Clarendon, 1908.

Jennings, R. Y., and A. Watts. Oppenheim's International Law. 9th ed. London: Longmans, 1992

Roberts, Adam, and Richard Guelff. Documents on the Laws of War. Oxford: Clarendon, 1989.

Taylor, Telford. The Anatomy of the Nuremberg Trials: A Personal Memoir. New York: Knopf, 1992.

United States. War Department. General Staff. Rules of Land Warfare. Washington, D.C.: Government Printing Office, 1914. U.S. Army field manual.

This entry contains information applicable to United States law only.

A body of customs, practices, usages, conventions, protocols, treaties, laws, and other norms that govern the commencement, conduct, and termination of hostilities between belligerent states or parties.

Frequently violated and sometimes ridiculed, the rules of war have evolved over centuries. They distinguish nations whose armed forces respect some minimal standard of human decency from terrorists, marauders, and other outlaws who use illegal and unrestricted methods of warfare to achieve political, economic, or military objectives.

Origins and Development

The modern rules of war trace their origins to the chivalric practices of medieval Europe. Feudal knights were bound by the law of chivalry, a customary code of conduct that could be enforced in local courts throughout western Europe by a military commander of any nation. Premised on notions of justice and fairness, the law of chivalry gave birth to the distinction between soldier and civilian and the idea that women, children, and older persons should be shielded from the bloody fields of combat. The Roman Catholic Church also influenced the development of these rules, differentiating between just and unjust wars and denouncing certain weapons as odious to God.

Codification of the rules of warfare began in the nineteenth century. In 1862 President Abraham Lincoln commissioned Francis Lieber to draft a code of regulations summarizing the laws and usages of war. A year later, Lieber submitted a draft that the executive branch promulgated as General Orders No. 1, entitled Instructions for the Government of Armies of the United States in the Field. Known as the Lieber code, this systematic articulation of the rules of war remained the official pronouncement of the U.S. Army for more than a half a century. It addressed the concept of military necessity, detailed the rights of prisoners, noncombatants, and spies, and discussed the use of poisons, unnecessary violence, and cruelty.

In 1864 the codification movement took on an international flavor when twelve nations signed a Convention for the Amelioration of the Condition of the Wounded in Armies in the Field, 129 Consol. T.S. 361, the first of a series of Red Cross initiatives for this purpose. In 1899 the United States, Mexico, Japan, Persia (now Iran), Siam (now Thailand), and nineteen other nations, including all of the major European powers, signed a Convention with Respect to the Laws and Customs of War, 187 Consol. T.S. 429, an initiative that followed the broad outlines of the Lieber code and also addressed the relationship between an occupying power and noncombatant civilian inhabitants. In 1914 the Lieber code was replaced by an army manual entitled The Law of Land Warfare, which is still in force today.

Codification of the international rules governing land, sea, and air warfare accelerated following the conclusions of the two World Wars, the Korean War, the Vietnam War, and the many other hostilities that have taken place during the twentieth century. In addition to building upon the principles previously established, this period witnessed the creation of several new concepts, including certain categories of war crimes, such as crimes against peace and crimes against humanity.

Crimes against peace are committed by persons who plan or wage aggressive wars. Crimes against humanity are committed by persons who knowingly participate in the deportation, enslavement, persecution, or programmatic extermination of certain segments of society during times of war. Soldiers, military leaders, political officials, members of the judiciary, industrialists, and civilians are all subject to prosecution for violating any of these rules of war.

Leaders and officials who wage aggressive war, disregard the territorial or political independence of another state, or violate the express terms of a peace settlement may be prosecuted as war criminals under the United Nations Charter. They may also be prosecuted under the Nuremberg principles, derived from the Nuremberg trials after World War II in which the Allied powers tried twenty-four leading Nazis for an assortment of war crimes, including crimes against peace and crimes against humanity. The Allies later prosecuted more than a hundred German civilians, including industrialists, doctors, and judges, who were enlisted by the Nazis to further their system of terror.

War, Terrorism, and Subversion

The rules of war do not apply to every act of hostility against an established government. Openly declared wars between sovereign states clearly implicate the rules of war. When the belligerents do not issue formal declarations of war, the legal status of a military conflict becomes murky. Isolated acts of terrorism or subversion, however, neither constitute acts of war nor create a state of war. Such acts are normally punishable under the criminal laws of the country in which they are perpetrated.

Wider internal disturbances within the territorial borders of a country are more difficult to classify. When such disturbances begin, the ruling government is apt to classify them as riots or rebellions, while those who cause the disturbances are likely to classify them as acts of civil war. International law provides no definitive classification for such hostilities. But subversive groups that acquire sustained control over substantial territory and win measurable domestic support are more likely to receive the benefit of the rules governing warfare than are small bands of insurgents whose seditious efforts are stifled and repelled.

Even when a state of war indisputably exists, the rules of war do not apply to all combatants. Regular land, air, and naval forces are typically governed by the rules of warfare. Irregular armed forces, such as guerrillas and other insurgents, are governed by these rules only when they carry their weapons openly, wear a recognizable emblem, conduct their operations in accordance with the laws of war, and are commanded by a superior who is responsible for subordinates.

The point of these rules is not only to distinguish combatants from noncombatants but to distinguish conventional soldiers from hired assassins, spies, and mercenaries who circumvent the customs of war in order to accomplish an end that could not be achieved by regular armed forces. Because assassins, spies, and mercenaries do not play by the rules of war, their captors need not either. Similarly, combatants who attempt to flout the rules of war by disguising themselves in civilian clothing or enemy uniforms may be treated as ordinary criminals, though most other methods of deceit are considered permissible tactics of warfare.

Prisoners of War

The difference between an ordinary criminal and a prisoner of war is important. An ordinary criminal may be detained, prosecuted, and punished in accordance with the domestic criminal laws of the country in which the crime is committed. A conventional soldier who is captured by the enemy must be humanely treated in accordance with the international rules of war. Under these rules prisoners of war are required to give their captors only enough information for identification, such as name, rank, serial number, and date of birth. Captors may not torture prisoners to extract information from them nor subject prisoners to punishment without first complying with specific legal procedures.

Under the rules of war, prisoners of war may not be punished for wrongs committed by the armed forces to which they belong, and medical and scientific experiments upon prisoners are forbidden. Captors must provide prisoners with sufficient food and beverages to maintain good health, and adequate standards of clothing, housing, sanitation, and hygiene are prescribed. To encourage accountability, captors are required to disclose the names of prisoners to the belligerent for which they were fighting when captured.

Although prisoners of war may be compelled to work while in captivity, they cannot be forced to contribute directly to the captor's war effort, and they must receive pay for their work on a scale commensurate with their rank. Prisoners are not permitted to harm their captors under the rules of war, but they may attempt to escape. Prisoners of war are entitled to full freedom of religion, and discrimination based on race, color, or ethnicity is prohibited. Given the breadth of these rights, prisoners of war often enjoy greater protection under the rules of war than they would under the domestic laws of their captor.

In certain cases being granted the status of prisoner of war can mean the difference between life and death. Summary execution of prisoners is expressly proscribed, as are orders to "take no prisoners" on the battlefield, which is tantamount to an order for their execution. The rules of war place other limitations on the use of capital punishment and affirmatively require captors to provide sick and wounded prisoners with medical care. Violations of these rules, though not uncommon in the heat of battle, are deterred by the threat of reprisal. Prisoner exchanges, which benefit both sides, also provide belligerents with incentive for reciprocal compliance with these rules.

Soldiers and Civilians

The difference between soldier and civilian is another important distinction under the rules of war. War is fought by trained soldiers armed with guns, tanks, and an assortment of other strategic weapons that they are authorized to use for tactical advantage, both offensive and defensive. The object of war is to thoroughly defeat an enemy by destroying its armed forces, which may be accomplished in an infinite number of ways, including killing and attrition. It is anticipated that much blood will be shed during a war, regardless of its length.

Civilians, by and large, are neither trained in combat nor armed, and they are not authorized to kill except in self-defense. However, civilians do have families to feed, mortgages to pay, and jobs to perform, obligations that are not suspended during times of war. Hence, the rules of war attempt to insulate civilians from many of the inconveniences, distractions, tragedies, and horrors of war.

War provides combatants with no immunity from ordinary criminal laws against rape and plunder, even when such transgressions are committed pursuant to an order given by a superior. Crimes committed against civilians because of their race, religion, and national origin, including genocide, are considered war crimes. Like prisoners of war, civilians may not be punished for wrongs committed by their government or military forces, and they may not be held as hostages under any circumstances.

Civilians may lose their protected status in certain circumstances. When insurgents or guerrillas live among the civilian population, soldiers may take measures to ferret out the enemy, including the use of interrogations, searches, and curfews. Although the individual liberty of civilians can be temporarily curtailed in such situations, it cannot be permanently eliminated. Protracted internment of entire villages or groups of civilians is not allowed. Civilian supporters who carry weapons or grenades forfeit their protected status, however, and may be detained as prisoners of war or saboteurs. If soldiers seek to destroy an entire village that is known to be an enemy stronghold, civilians must normally be informed of the action ahead of time and permitted to evacuate.

Military practice differs as to whether children, older persons, and pregnant women should be allowed egress from a besieged area. At the same time, it is common practice to permit clergy and medical personnel ingress to besieged locales. Once a besieged area has been overtaken, the military is considered an occupying power with the responsibility to administer the laws for the preservation of public order and public safety. Supplies of food and hospital services must be ensured.

Military Occupation

Although an occupying power may exercise dominion over a conquered nation and acquires actual authority to administer the law, complete sovereignty is not transferred until a treaty or other settlement has been reached. An occupying power is not bound by the constitution or laws of the territory occupied, but it is prohibited from altering them except in cases of military necessity. Inhabitants owe no duty of allegiance to an occupying power during a state of martial law.

Occupation is an important aim of warfare, enabling a belligerent to exploit an enemy's resources and deny them to a foe. The occupying power may seize any governmental property that is necessary for military operations but may not sell public land or buildings. Municipalities and institutions dedicated to religion, charity, education, arts, and sciences are exempt from seizure. The status of public officials, including members of the judiciary, cannot be changed by the occupying power, although officials can be removed for misconduct or asked to retire. Any system of public education must be allowed to continue.

Taxes may be collected from local residents, but the basic tax structure should remain intact. The occupying power is not permitted to destroy private property, except in cases of military necessity, and must fairly compensate individuals from whom it confiscates personal belongings. The occupying power may require private residents to house its troops, but the troops must honor familial rights, religious practices, and other customs in the community. In response to military occupation, allies of the conquered nation may freeze its assets or establish a naval blockade around the occupied territory.

Aerial Warfare

Protection of civilian populations is also a primary concern of the rules governing aerial warfare. Indiscriminate bombing of undefended cities or other areas densely inhabited by civilians is considered a serious war crime. Aerial bombardment of private property that is unrelated to military operations, such as private homes, commercial establishments, philanthropic institutions, historical landmarks, and educational facilities, is also forbidden. Aerial assaults on hospitals, public or private, are banned as well.

The incidental destruction of private property during an aerial attack may not violate the rules of war, however, if the attack is carried out for military purposes. These include the interdiction of military communication and transportation, the enervation of military forces and installations, and the destruction of factories manufacturing arms or military supplies. Nonetheless, the bombing of such targets may be illegal if it endangers high concentrations of civilians, and the stated military objective is unclear or unimportant.

Rules regarding aerial warfare are frequently violated. During World War II, both the Axis and the Allied powers engaged in bombing attacks that inflicted high casualties directly on civilian populations. In the Battle of Britain, the German Luftwaffe bombed certain English cities to weaken the residents' will to resist. The Allies bombed Dresden and Hamburg in Germany and Tokyo, Yokohama, Hiroshima, and Nagasaki in Japan without discriminating between military and noncombatant targets. Since World War II, improved fighter planes and anti-aircraft defenses have made surgical aerial assaults more difficult.

Aircraft must be identified by external markings to allow belligerents to distinguish military from civilian aerial units. Additionally, such markings allow neutral countries to identify their own aircraft and permit the peaceful entry of aerial medical units onto a battlefield. Regardless of the nature of an aerial unit, belligerents are prohibited from firing on persons parachuting from a disabled aircraft, unless they are paratroopers engaged in an espionage mission. Distinguishing paratroopers from other parachutists is left to the discretion of individual pilots and gunners.

Naval Warfare

The rules governing naval warfare also leave much discretion to the participants. Although belligerent warships may attack and sink an enemy warship encountered on the high seas, they may neither sink nor attack an enemy merchant ship unless it refuses to obey a signal to stop and submit to inspection. Conversely, belligerent merchant ships are not obliged to stop or submit to inspection but may attempt to escape or act in self-defense. However, the line separating an act of self-defense from an offensive maneuver is subject to some debate. In 1916 a British merchant ship captain was court-martialed for ramming a German U-boat, despite the captain's claim that his vessel was acting in self-defense.

When an enemy warship has been captured, it becomes the property of the captor and may be sunk or brought into port. If an enemy merchant ship is captured, it must be taken into port for adjudication regarding the ownership of the vessel and its cargo pursuant to international law. In either case the passengers and crew of a captured ship may not be harmed. Captured members of enemy naval forces are entitled to treatment as prisoners of war. Shipwrecked belligerents are also entitled to humane treatment under the rules of war and may not be abandoned or refused quarter. Many of the same rules governing surface warships have been applied to submarine warfare as well.

Weapons

All military forces, land, air, and sea, are restricted as to the type of weapons and explosives they may employ. Military forces may not use arms, projectiles, or other materials calculated to cause unnecessary suffering, such as weapons that leave fragments of glass and plastic in the body. The United Nations has condemned thermal nuclear weapons because of their propensity to inflict unnecessary suffering and their inability to discriminate between combatants and noncombatants, or military and nonmilitary targets.

The use of poisons, poisoned weapons, and poisonous gases by any branch of the armed forces is flatly prohibited, as is the use of bacteriological materials and devices that spread disease. However, incendiary weapons, such as napalm, and chemical herbicides, such as Agent Orange, have been employed by military tacticians when enemy forces conceal themselves in a jungle or forest. Several countries have objected to the use of chemical and incendiary weapons even for such limited purposes.

Neutral Countries

All military forces are similarly bound by the rules of war with regard to neutral countries. By definition a neutral country is not a party to a military conflict between belligerent states. Unless bound by a treaty, governments are not required to remain neutral in a war, but they are presumed to be neutral unless they manifest adherence to one side or the other by word or act. Neutral countries must neither help nor harm a belligerent state, nor allow a belligerent to make use of their territory or resources for military purposes. Instead, neutral states must assume a position of strict impartiality.

Neutral territory is considered an asylum for prisoners of war, who become free upon reaching neutral ground. Belligerent troops may enter neutral territory to avoid capture but may be rejected or disarmed by the host country. Belligerent aircraft are not permitted to enter neutral airspace, and if they land, the host country may intern them. Belligerent warships may be granted asylum when they are in distress or in need of repairs. If belligerents abuse this privilege, however, asylum may be revoked, and their forces may be ordered to leave.

Lawful and Unlawful Wars

The only type of war recognized by the United Nations as lawful is one fought in self-defense. The rules of warfare are not suspended, however, or otherwise rendered inapplicable merely because the grounds for fighting a particular war are unlawful. In an illegal war both the aggressor and other belligerents must still comport their behavior with the international customs, practices, and conventions of war. At the same time, some authority suggests that one belligerent may disregard certain rules of war in reprisal for its enemy's disregard of the same rules. Such reprisals have a tendency to spiral downward, however, with each act of retaliation straying further from the lawful norms of warfare.

Enforcement

It is sometimes observed that the phrase rules of war constitutes an oxymoron because the business of war is treachery and chaos while rules and regulations seek to impose order and structure. No permanent and impartial international body has been created to administer the rules of war. Although the United Nations has acted with multinational support in the Korean and Gulf Wars, and the International Court of Justice has adjudicated claims against democratic and totalitarian regimes alike, neither body exercises sovereignty over individual member states in any meaningful sense, and powerful countries generally wield more influence over these bodies than do weaker countries.

In most instances it is left to the victorious powers to enforce the rules of war. Following World War II, for example, the Allies prosecuted the Axis powers in Europe and the South Pacific despite the claims of the vanquished that such proceedings amounted to little more than victor's justice, or revenge. These claims were not entirely hollow, in that the Allies had committed a variety of war crimes themselves. During the course of the war, for example, the United States interned more than a hundred thousand Americans of Japanese descent simply because of their ancestry; the British bombed civilian populations in Germany; and the Russians massacred Polish soldiers in the Katyn Forest.

Thus, the current system of international law remains imperfect. Nonetheless, international law attempts to embody the rudiments of human decency, rudiments that are reflected by the customs, practices, and rules of war.

See: Armed Services; Arms Control and Disarmament; Court-Martial; Hirohito; Hitler, Adolf; Human Rights; Japanese American Evacuation Cases; Just War; Korematsu v. United States; Military Government; Military Law; Militia; Neutrality; Prize Law; Uniform Code of Military Justice.

(DOD) That part of international law that regulates the conduct of armed hostilities. Also called the law of armed conflict. See also rules of engagement.

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