Law of war

The law of war is a specific branch of international law. It regulates two very different aspects of armed conflict. The first is called jus ad bellum, which governs the reasons a nation may start a war. The second is called jus in bello, which governs how people must behave during the fighting. These laws define important concepts like sovereignty, nationhood, and territory. They also address how to handle occupation and the acceptance of surrender. By setting these rules, the law of war attempts to manage the chaos of conflict through legal structures.

Modern laws of war are built upon three primary sources. The first source is lawmaking treaties, also known as conventions. These are formal, written agreements between nations. The second source is custom, or customary international law. This refers to the long-standing practices of nations that are accepted as legal requirements. The third source is general principles. These are fundamental ideas, such as distinction and proportionality, that provide basic guidance for the use of force. Together, these sources create a framework that limits what states can and cannot do during a conflict.

There are several core principles that guide the conduct of hostilities. The principle of distinction requires that combatants always distinguish between fighters and civilians. The principle of military necessity states that actions must be intended to help defeat an enemy and must target legitimate military objectives. Proportionality ensures that the force used is not excessive compared to the military goal. Additionally, the law prohibits attacks on those who are hors de combat, which means people who are no longer able to fight. Finally, the law forbids the infliction of unnecessary suffering through certain weapons or methods.

Humanity has attempted to limit the violence of war for thousands of years. In 1750 B.C., King Hammurabi of Babylon established a code of conduct for war. One rule in his code protected the environment by forbidding the cutting of fruit trees during a siege. In the 7th century, the first Sunni Muslim caliph, Abu Bakr, instructed his army to avoid harming children, women, and the elderly. In 697, Adomnan of Iona introduced the Law of the Innocents in Ireland and Scotland. This law specifically banned the destruction of churches and the killing of women and children. These early examples show a long history of trying to protect non-combatants.

The 19th century marked a major shift toward modern, written laws. Historian Geoffrey Best described the period from 1856 to 1909 as the "epoch of highest repute" for the law of war. During this time, nations moved away from rules based on religion or chivalry. Instead, they began using multilateral treaties to codify their agreements. For example, the Treaty of Armistice and Regularization of War in 1820 served as a precursor to international humanitarian law. In 1848, the Treaty of Guadalupe Hidalgo between the United States and Mexico included rules for protecting civilians. During the American Civil War, the Lieber Code helped develop the laws of land warfare.

Significant international agreements have further shaped these protections. In 1864, twelve countries signed the First Geneva Convention. This agreement was designed to protect hospital and ambulance crews during conflicts.

Later, between 1899 and 1907, the Hague Conventions were issued following two major peace conferences. These conferences were intended to limit the development of armaments and seek durable peace. The Nuremberg War Trials later helped clarify that many of these treaties had become customary laws. This meant they were binding on all parties, even if a specific nation had not signed a particular treaty.

The purpose of these laws is to mitigate the hardships caused by war. They aim to protect the wounded, the sick, and prisoners of war. They also work to safeguard the fundamental human rights of children and civilians. By establishing clear rules for the start and end of a conflict, these laws help facilitate the restoration of peace. However, the law of war must constantly adapt to new technologies and situations. For instance, there is ongoing scientific and legal debate regarding the use of depleted uranium projectiles. As conflict methods change, international legal circles continue to discuss how to apply general principles to new challenges.