Warfare has been a common element in interstate conduct since the dawn of civilization, and has been constantly evolving and changing as technology and strategy develops. Like many other facets of international interaction, the conduct of warfare has been subject to a number of limitations, treaties, and agreements concerning its nature. Similarly, the targets of war and weapons employed have too been limited and selectively chosen by the international community. The modern conduct of war is now limited and regulated by a wide array of treaties and laws, though the governing of war has had a long and varied history. Understanding the sources and history of these rules of war, as well as why they exist, serves to help international legal scholars understand the conduct of nations during conflict.

The sources of the laws of war are similar to the sources of all international laws and regulations: treaties and international conventions, international customs and traditions, and general principles of law recognized by civilized nations. International treaties and conventions covering issues related to war have massively shaped the nature and conduct of war in the past century, especially as the binding nature of treaties has increased substantially during that period. These treaties, however, have largely codified previous international customs and traditions regarding warfare. These customs are developed as large numbers of states adhere to the same principles or practices and view these practices as generally obligatory. Additionally, states develop laws of war around general principles, which are commonly accepted beliefs and truths about the nature of war. These principles include a belief that violence should not be allowed beyond the point of necessity, and that a degree of ‘chivalry’, which demands a certain amount of fairness and mutual respect between the opposing forces, be maintained.[1]

Armed conflict has been around since the dawn of civilization and with this armed conflict has come laws and agreements governing the use of force. The earliest known examples of governing the conduct of war are found in the Hebrew Old Testament. Deuteronomy 20: 19-20 limited the amount of acceptable collateral and environmental damage during a siege, while Deuteronomy 21: 10-14 required that female captives could not be sold off as slaves.[2] Early Christian thinkers theorized about the ethical nature of war, and attempted to codify what they determined as a ‘just war’. The ideas of St. Augustine would later be used by the priest Thomas Aquinas to determine what circumstances made a war just. He argued that a war must occur for good and a just purpose instead of self-gain or as an exercise in power, the war must be waged by and against a properly instituted authority such as the state, and that peace must be a central motive even in the midst of violence.[3] In the 7th century Arab world, the first Muslim Caliph, Abu Bakr, commanded his army to spare women, children, and the elderly, to leave trees standing, not to ravage the enemy’s livestock, not to mutilate dead bodies, and to leave monks alone. Furthermore, scripture in the Koran commanded Muslims only to strike their enemy in self-defense, and to spare enemies on the retreat.[4]

Laws governing the conduct of war were present in East Asia throughout much of history, as well. In the Chunqui Period of ancient China, feudal lords organized conferences on the elimination of war and disarmament in the Chinese state of Song. During the Warring States period, rules existed amongst the seven feudal states regarding the declaration of war, the conclusion of peace, and the favorable treatment of prisoners of war, as well as rules that called for the sparing of retreating enemies and the elderly, prohibitions on surprise attacks and ruses, and protection for the wounded.[5] These rules, while setting precedents regarding conflict and codifying norms which spread across the Asian region, were not strictly adhered. Historical accounts of a battle during this era describe how the King of Qin ordered the live burial of as many as 400,000 prisoners of war, for example.[6]

Early Medieval movements in Christian Europe also attempted to limit the scope of warfare and protect noncombatants. The ‘Peace and Truce of God’ was a movement by the Catholic Church that applied spiritual sanctions in order to limit the violence of private war in the feudal society. Its origins were in the years following the collapse of the Carolingian Empire in the ninth century, during which time France had devolved into many small feudal holdings fighting against each other. The Truce of God attempted to intimidate nobles and knights into committing to peace and renouncing private wars by intimidating them with sacred relics. Certain days of the year were also set aside where violence was not allowed. The Peace of God was a proclamation issued by local clergy that granted immunity from violence to defenseless noncombatants. While the movements were unsuccessful in attempting to control warfare in the violent reality of feudal society, the precedents set by them (sparing noncombatants and controlling violence) would permeate through Medieval society and be attempted by successive movements.[7] During the 14th and 15th centuries, the institution of neutrality began to develop. Treaties containing provisions on neutrality were signed, initially meaning that one party refused to aid belligerents in war, and then including stipulations that belligerents should not attack the neutral subject. Additionally, maritime military law began to develop during the Middle Ages. ‘Prize Law’, which covered the plunder of captured enemy ships and maritime trade, was codified during this period. Prohibitions on the trading of goods with the enemy or the transportation of goods on behalf of the enemy were created, as well as provisions on the fate of captured ships. Additionally, the institution of privateering began around the 14th century, and decrees were issued outlining the methods of granting permits to privateers that would render them legitimate.[8] Hugo Grotius, a Renaissance international legal scholar, would discuss the law and nature of war in his “De Jure Belli ac Pacis” in 1625. He identified three ‘just causes for war’ as being self-defense, reparation of injury, and punishment. He further identified rules that govern the conduct of war, and that all parts to war are bound to those rules, whether their cause is just or not.[9]

The invention and development of firearms in the 18th and 19th centuries and more advanced science and technology accelerated the advent of new ways of war, as well as the increased killing potential and brutality of conflict. In response to this, the conduct of warring entities was standardized in order to limit to decrease the destructive capability of war. The 1865 Declaration of Paris abolished privateering, made enemy goods shipped under a neutral flag a non-target, and made blockades binding only if they are effective in maintaining a force sufficient to prevent access to the enemy coast. The First Geneva Convention of 1864 dealt with the humane treatment of the wounded and the sick in armed forces on the field. It protected soldiers from inhumane treatment, that the dead should have their information and identity recorded, that this information should be transmitted, and that impartial humanitarian organizations should provide protection and relief for the wounded. The St. Petersburg Declaration of 1868 banned the use of fragmenting, explosive, and incendiary small arms ammunition. Delegates affirmed that the only legitimate object of war should be to weaken the military force of the enemy. The first Hague Peace Conference followed this on May 18, 1899. It was convened with 26 participating states, and its purpose was to ‘limit arms and to safeguard peace’. The Second Geneva Convention in 1906 dealt required belligerent parties to protect and care for the shipwrecked, prohibited the capture of neutral vessels, and made hospital and humanitarian ships non-targets. The Second Hague Peace Conference of 1906-1907 concentrated on the issue of laws of war. It prohibited the launching of projectiles and explosives from balloons and included conventions which stipulated that war could not begin unless there is advanced and explicit warning, made distinctions between combatants and noncombatants, called for the humane treatment of prisoners of war, prohibited the destruction or confiscation of enemy property, and protected cultural and historical landmarks as well a medical facilities. Additional conventions stated that, during occupation, the occupying power must restore and ensure public order and safety as well as the laws of the nation they are occupying and that neutrality must be respected. Many laws of naval war were also codified, including the status of enemy merchant ships, the laying of submarine mines and bombardment, the obligations of neutral powers during naval war, and the issue of blockades. The London Naval Conference of 1908-1909 added to these laws of naval war. The Geneva Convention of 1929 dealt with the definition of, the protection of, and humane treatment of prisoners of war, specifying the type of labor they were permitted to do and the terms of their captivity.[10]

The Second World War was a catastrophic event for human society, and each of the belligerent powers violated the laws of armed conflict. At the end of the war, representatives of a large number of states converged in Geneva, and deliberated on the formulation and regulation of new laws on conduct during war. On August 12, 1949, 63 states signed the new Geneva Conventions. These new articles updated and supplemented all of the prior Geneva conventions. It covered the affirmation that the sick and wounded of any party shall receive impartial treatment, and are prohibited to be killed, tortured, or subject to experimentation, that naval medical personnel, ships, and wounded must be protected, that civilians in the power of a belligerent party shall receive protection and humane treatment, that civilian settlements must not be destroyed, and that social norms (cultural, religious, etc.) must be respected. The rules included in the Conventions of 1949 are applicable to all armed conflicts, declared or not, each convention is binding to each belligerent party in a war, regardless of whether all parties are signatory, the rules adhere in conflicts of intranational scope, such as civil wars, and guarantees that the victims of such wars receive minimum protection.[11] Additionally, in 1977, representatives from all of the states gathered in Geneva and signed the ‘Protocols Additional to the Four Geneva Conventions of 1949’. These protocols expanded the scope of the Geneva conventions to include situations to which the convention is applicable to armed conflicts over colonial domination, alien occupation and racist regimes, as well as largely increasing the number of provisions regarding the protection of unoccupied territories and civilians, and strengthening protection of civilians. The Treaty on the Non-Proliferation of Nuclear Weapons, which became a force of law in 1970, specified that states should not produce, and thus proliferate, nuclear weaponry, and that nuclear-armed states should begin to disarm their arsenals. The Anti-Ballistic Missile Treaty, signed into law in 1972, specified that the United States and the Soviet Union should limit their anti-ballistic missile arsenals, therefore allowing for the possibility of ‘mutually-assured-destruction’ and thus serving to reinforce the deterrent effect of nuclear weapons.

There have been many recent developments in the law of war. The Geneva Convention of October 10, 1980, on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effect, prohibited weapon systems that could cause too much injury or cause too much collateral damage. Included among these weapon systems were cluster-bomb munitions and landmines. In October 1995, the Vienna Diplomatic Conference issued the Protocol on Blinding Laser Weapons, which prohibiting the use and transfer of laser weapons whose functions are to cause permanent blindness. The Convention on the Prohibition on the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on Their Destruction, signed in 1997 by 121 states, made the use of landmines illegal in war and discussed their destruction. The START treaties between the United States and Russia, signed in 1991 and reaffirmed in 2010, largely reduced the amount of strategic nuclear weapons that the two countries could possess, as well as other forms of strategic weaponry. These treaties would become the largest and most comprehensive arms reduction treaties in history.[12]

The development of the United Nations following the Second World War would change the way that states could declare and justify war. The charter of the United Nations declares that states should resolve all of their conflicts peacefully, theoretically eliminating the justification for war. However, Article 41 of the United Nations specifies, “nothing in the present Charter shall impair the inherent right of individual or collective self-defense if an armed attack occurs against a Member of the United Nations, until such time as the Security Council takes the measures necessary to maintain international peace and security”. Thus, nations are only justified in waging war if they are doing so in self-defense against an attack. Article 42 of the United Nations Charter stipulates that, “Should the Security Council consider that measures provided for in Article 41 [which discusses sanctions and diplomatic coercive measures] are inadequate or have proved to be inadequate, it may take such action by air, sea or land forces as may be necessary to maintain or restore international peace and security”. The Security Council of the United Nations thus operates as a governing council which decides when armed conflict is justifiable. Additionally, it is through the Security Council that the use of armed force can be called for or sanctioned. The significance of the Security Council and the United Nations is that they govern the declaration of war, and that all wars that are ‘acceptable’ to the international community must thus come with the support of the United Nations.[13]

Despite the codification and prevalence of laws of war, states and leaders are susceptible to violating them. In cases of intentional disregard for the laws of war, the development of international criminal justice can provide a safeguard and method to prosecute violators. In 1945, the Soviet Union, the United States, the United Kingdom and France agreed to establish an International Military Tribunal, and signed the Agreement for the Prosecution and Punishment of the Major War Criminals of the European Axis as well as the Charter of the International Military Tribunal. These Tribunals would, according to the charters, prosecute ‘crimes against peace’, which included the planning, preparation, initiation or waging of a war or aggression, or a war in violation of international treaties, agreements or assurances, ‘war crimes’, which are violations of the laws or customs of war, and ‘crimes against humanity’, which involve murder, extermination, enslavement, deportation and other inhumane acts committed against any civilian population before or during the war. The Nuremburg Trials against the defeat Nazi leadership and the Tokyo Trials against the Japanese leadership following World War Two were applications of these trials, and convicted much of the upper leadership of the defeated Germany and Japan of war crimes, setting a precedent for international trials against war crimes.[14] In 1993, the United Nations Security Council established an International Criminal Tribunal for the Former Yugoslavia which prosecuted the people responsible for violations of international humanitarian law since 1991 during conflicts in the Balkans. Additionally, in 1994, the United Nations Security Council established an International Criminal Tribunal for Rwanda to prosecute those responsible for genocide and other serious violations of international humanitarian law in Rwanda during its civil war and subsequent genocide. The passing of the Rome Statute of the International Criminal Court in 1998 was also an important step in ensuring that all states abide by international humanitarian law. The newly established International Criminal Court was given jurisdiction over all war crimes. These new precedents in the legal traditions of the international community regarding the laws of war mean that those who violate the accepted laws are susceptible to trial and prosecution by international legal bodies. The hope is that this will serve as a deterrent for the committing of further war crimes.

Thus, the international community has developed rules, norms, and regulations governing war in response to purposes and principles regarding conflict and in order to mitigate hardships and problems that arise from war. The law of war attempts to facilitate the realization of these principles, while also governing the conduct of war in order to prevent certain actions that could set them back. These principles include the end goal of ending hostilities quickly, hopes for limited wars, and the protection of people and property from conflict. The hardships that the laws of war hope to mitigate thus include the destruction of noncombatant property and life, the disregard for human rights, and the declarations of ‘unjust’ wars.

One of the primary guiding principles behind the laws of war is the hope that peace will be restored quickly. This is generally only possible when the belligerent parties fight wars of limited scope and intensity, and with limited goals. The nature of war means that states will use the maximum extent of their force in order to achieve their goals, while also reciprocating the actions that their enemies make. Because of this, laws are needed to govern the amount of force that can be used, and what tools and weapons can be utilized during wartime. Without these laws, states would not be prohibited from using their arsenals or developing strategies that would cause massive devastation and destruction in their adversary’s territory. Additionally, the reciprocal nature of war means that all of the belligerent parties could expect their territory to be devastated by the enemy. This “eye-for-an-eye” philosophy, if allowed to develop, would thus lead to sustained and harrowing losses on either party to any particular conflict. Because states will also use the maximum extent of their force in order to achieve their wartime goals, the laws of war hope to limit the scope, goals, and justifications for war. Laws governing when and how a state can declare war limits the reasons a state can use to declare war, and thus lessens the ‘availability’ of destructive conflict as a policy tool. The hope is that, through the limiting of the scope and scale of wars and thus the intensity of the conflict, diplomatic solutions to the issue being fought over can be found.

The principle of limited war is realized through the limitation of massively destructive weapons systems, as well as providing conduits through which states must go in order to declare war. The United Nations charters, and the United Nations Security Council, are now the governing and regulating bodies when it comes to the declaration and justification of war. States must receive the sanction of the Security Council prior to declaring war on other states, unless they have already first come under attack. Because of this, the amount of wars which are ‘legitimate’ in the international community should decrease. The Security Council adheres to the principles of a ‘just war’, meaning that the ‘casus belli’, or cause for war, should only be fought to redress a wrong which has been suffered, if the violence inflicted is proportional to the wrong suffered, if it is fought with a reasonable chance for success, if the ultimate goal is to reestablish peace, and if the war is only fought as a last resort.[15] According to these specifications, the amount of legitimate wars should be small, considering that most ‘wrongs’ could be resolved diplomatically or not considered as a reason for war, and the conduct and violence of those wars would be limited, for they should be proportional to the amount of force necessary to redress a wrong which was suffered. Limiting destructive weapons systems assists in limiting wars because they reduce the amount of destruction, collateral and intentional, which could be inflicted upon the enemy. The infliction of much destruction and damage would prompt an equal response from an adversary, and would likely escalate the conduct and scope of the war into a ‘total war’. Thus, by limiting destructive munitions or overly-lethal weapons systems, the conduct of war would remain light and limited, and the reciprocation between adversaries would therefore also be limited.

The protection of human life and civilian property is also an important principle behind the laws of war. The protection of civilians is conducive to the ultimate goal of peace: the destruction of cities and civilian property would make populations more dedicated to fight until the end, or make them more hostile towards the adversary. That aside, the protection of civilians is an important principle because of the way states view the nature of war. War is supposed to be fought only as a continuation of policy, and in order to achieve a political goal. The conduct of war is only to destroy and eliminate the adversary’s military capacity. The indiscriminate slaughter of civilians or the destruction of non-military property does not assist in the destruction of military strength, nor does it assist in the end goal of achieving a political policy. Rather, states view it as a simply inhumane act. It is because of this that civilian populations are protected under a number of conventions and treaties regarding the laws of war, and additionally weapons systems which inflict large amounts of collateral damage or do not explicitly target military targets are limited or prohibited under a number of regulations on the conduct of war.

The development of the laws of war has had a long and varied history, beginning in ancient times and continuing till today. The massive expansion of international laws, regulations, and organizations in the last century has assisted in expanding the scope of international laws of war as well as driven the codification and development of many regulations on the conduct and weapons of war. These developments are likely to continue, as more and more sophisticated weapons systems become developed and enter service and as new forms of combat and different adversaries begin to appear. Additionally, these laws of war will change and bend according to the changing nature and participants of war. Recent developments in the legal aspect of the international community, such as the development of the International Criminal Court and the Nuremburg and Tokyo Trials following World War Two, means that violators of the laws of war will be prosecuted for their actions. A legal precedent has thus been set which will help enforce the laws of war, and will make potential violators more weary of disregarding them.

The laws of war are now enforced by legal international councils and bodies, and are largely regulated by international laws and regulations. States adhere to the accepted rules of conduct in fear of reciprocation by their adversaries as well as their international reputation. Leaders fear prosecution under international tribunals should they violate the laws of war. These laws serve an ultimate purpose of realizing a number of general principles accepted by the international community regarding war and its conduct: the realization of peace, the protection of human life and civilian property, the concepts of ‘just’ wars, and wars of limited scope and scale. Because of the laws of war, the world has seen a decrease in the lethality and destructive ability of armed conflict, as well as general decline in the amount of wars fought between states.

Works Cited

[1] General Principles & Sources of The Law, Law of War, http://lawofwar.org/principles.htm, Accessed 20 Apr. 2012

[2] Deuteronomy, Chapter 20, University of Virginia Library, http://etext.virginia.edu/etcbin/toccer-new2?id=KjvDeut.sgm&images=images/modeng&data=/texts/english/modeng/parsed&tag=public&part=20&division=div,Accessed 18 Apr. 2012

[3] Aquinas, Thomas, The Just War, Catholic Education Resource Center, http://www.catholiceducation.org/articles/politics/pg0029.html. Accessed 18. Apr. 2012

[4] 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

[5] Wang Tieya, ed., Guojifa (International Law) (Beijing: Falu chubanshe, 1981), p. 509; Sun Yurong, Gudai Zhongguo guojifa yanjiu (Study on International Law in Ancient China) (Beijing: China University of Political Science and Law Press, 1999), pp. 182–90.

[6] Sima Qian, Shiji: Qin benji (Historical Chronicles: Qin Almanac).

[7] Jordan, William Chester. Europe in the High Middle Ages. London: Viking, 2003.

[8] Firdman and Bastin, History of International Law. Moscow: International Relations Press, 1990

[9] The Law of War and Peace, trans. Francis Kelsey. Carnegie edition, 1925, Prol. sect. 28.

[10] International Committee of the Red Cross, International Law Concerning the Conduct of Hostilities: Collection of Hague Conventions and Some Other International Instruments. Geneva: International Committee of the Red Cross, 1989, p. 69.

[11] Roberts and Guelff, eds, Documents on the Laws of War. Oxford: Oxford University Press, 2000.

[12] Strategic Arms Reduction Treaty (START I): Executive Summary. The Office of Treaty Compliance. Retrieved 25 Apr. 2012

[13] Rupert Ticehurst, The Martens Clause and the Laws of Armed Conflict, Selected Articles From The International Review of The Red Cross, p. 28.

[14] Edoardo Greppi, The Evolution of Individual Criminal Responsibility Under International Law

[15] Kathryn Jean Lopez, Justice in War: Just-war theory, National Review Online, 15 October 2001