Rules of War

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Rules of War

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 12 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 19 other nations, including all 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 continued in the early 2000s to be enforced.

Codification of the international rules governing land, sea, and air warfare accelerated following the conclusions of World Wars I and II, the Korean War, the Vietnam War, and the many other hostilities that took 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 24 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 uniforms clearly displaying a recognizable emblem or insignia, 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 comply with 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.

They may also be treated as "enemy" or "unlawful" combatants, a kind of purgatory between civilian status and prisoner-of-war-status. In response to the September 11th Attacks in 2001, the United States launched a War on Terrorism, which included a specific military operation against the Taliban government in Afghanistan and members of the al Qaeda terrorist organization conducting operations there. During that conflict, the U.S. military captured thousands of Taliban and al Qaeda forces, hundreds of whom were allegedly not complying with the rules of war, failing to wear uniforms with insignia clearly displayed, failing to carry their weapons openly, and failing to organize themselves in units subject to a hierarchical chain of command.

The United States transported approximately 650 of the captured combatants to Camp X-Ray at the naval base in Guantanamo Bay, Cuba, where they were held as "enemy" or "unlawful" combatants for the duration of the war against terrorism. President george w. bush issued a series of executive orders that formally denied the Guantanamo detainees prisoner-of-war-status and created military tribunals or commissions to try them for possible war crimes. Despite criticism from international observers who sought prisoner-of-war-status for the Guantanamo detainees, at least two U.S courts of appeal have allowed the president's orders to stand, one declining to exercise jurisdiction over the matter, Al Odah v. U.S., 321 F.3d 1134 (D.C. Cir. 2003), and one denying that the petitioners had standing to challenge the detention, Coalition of Clergy, Lawyers & Professors v. Bush, 310 F.3d 1153, 1165 (9th Cir.2002). However, as of June 2003, no detainee had yet to appear before such a tribunal.

Prisoners of War

The difference between an ordinary criminal, an Enemy Combatant, 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. An enemy combatant may be detained and interrogated on foreign soil while hostilities are ongoing, without the benefit of counsel, the right to file a Habeas Corpus petition, or other fundamental liberties afforded by the U.S. Constitution or international law. 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. According to the rules, captors may not torture prisoners to extract information from them or 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. Without discriminating between military and noncombatant targets, the Allies bombed Dresden and Hamburg in Germany and Tokyo and Yokohama, and the United States dropped the atomic bomb on Hiroshima and Nagasaki in Japan, killing over 100,000 Japanese civilians in the first ten seconds after the first blast. 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 attack nor sink 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.


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, U.S. tacticians used incendiary weapons, such as napalm, and chemical herbicides, such as Agent Orange, when enemy forces concealed 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.


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 and dropped the atomic bomb on two Japanese cities; 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.

Further readings

Green, L.C. 1996. "Enforcement of the Law in International and Non-international Conflicts." Denver Journal of International Law and Policy 24.

Howard, Michael, George J. Andreopoulos, and Mark R. Shulman, eds. 1994. The Laws of War: Constraints on Warfare in the Western World. New Haven, Conn.: Yale Univ. Press.

Jochnick, Chris, and Roger Normand. 1994. "The Legitimation of Violence: A Critical History of the Laws of War." Harvard International Law Journal 35.

Mitchell, Dennis. 1996. "All Is Not Fair in War: The Need for a Permanent War Crimes Tribunal." Drake Law Review 44.

Reisman, W. Michael, and Chris T. Antoniou, eds. 1994. The Laws of War: A Comprehensive Collection of Primary Documents on International Laws Governing Armed Conflict. New York: Vintage.

Taylor, Telford. 1992. The Anatomy of the Nuremberg Trials. Toronto: Little, Brown.

Walzer, Michael. 1992. Just and Unjust Wars: A Moral Argument with Historical Illustrations. New York: Basic Books.


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; Tokyo Trial; Uniform Code of Military Justice.

West's Encyclopedia of American Law, edition 2. Copyright 2008 The Gale Group, Inc. All rights reserved.
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