War crimes are "violations of the laws or customs of war", including but not limited to "murder, the ill-treatment or deportation of civilian residents of an occupied territory to slave labor camps", "the murder or ill-treatment of prisoners of war", the killing of hostages, "the wanton destruction of cities, towns and villages, and any devastation not justified by military necessity"
War crimes such as perfidy have existed for many centuries as customary law between civilised countries. Many of these customary laws were clarified in the Hague Conventions of 1899 and 1907. The modern concept of war crime was further developed under the auspices of the Nuremberg Trials based on the definition in the London Charter that was published on August 8, 1945. Along with war crimes the charter also defined crimes against peace and crimes against humanity, which are often committed during wars and in concert with war crimes, but are different offenses under international law.
Article 22 of the Hague IV ("Laws of War: Laws and Customs of War on Land (Hague IV); October 18, 1907") states that "The right of belligerents to adopt means of injuring the enemy is not unlimited" and over the last century many other treaties have introduced positive laws that place constraints on belligerents (see International treaties on the laws of war). Some of the provisions, such as those in the Hague conventions, are considered to be part of customary international law, and are binding on all. Others are only binding on individuals if the belligerent power to which they belong is a party to the treaty which introduced the constraint.
War crimes includes violations of established protections of the laws of war, but also include failures to adhere to norms of procedure and rules of battle, such as attacking those displaying a flag of truce, or using that same flag as a ruse of war to mount an attack. Attacking enemy troops while they are being deployed by way of a parachute is not a war crime. However, Protocol I, Article 42 of the Geneva Conventions explicitly forbids attacking parachutists who eject from damaged airplanes, and surrendering parachutists once landed. War crimes include such acts as mistreatment of prisoners of war or civilians. War crimes are sometimes part of instances of mass murder and genocide though these crimes are more broadly covered under international humanitarian law described as crimes against humanity.
War crimes are significant in international humanitarian law because it is an area where international tribunals such as the Nuremberg Trials and Tokyo trials have been convened. Recent examples are the International Criminal Tribunal for the Former Yugoslavia and the International Criminal Tribunal for Rwanda, which were established by the UN Security Council acting under Chapter VII of the UN Charter.
Under the Nuremberg Principles, war crimes are different from crimes against peace which is planning, preparing, initiating, or waging a war of aggression, or a war in violation of international treaties, agreements, or assurances.
On July 1, 2002, the International Criminal Court, a treaty-based court located in The Hague, came into being for the prosecution of war crimes committed on or after that date. However, several nations, most notably the United States, China, and Israel, have criticized the court and refuse to participate in it or to permit the court to have jurisdiction over their citizens. Note, however, that a citizen of one of the 'objector nations' could still find himself before the Court if he were accused of committing war crimes in a country that was a state party, regardless of the fact that their country of origin was not a signatory.
War crimes are defined in the statute that established the International Criminal Court, which includes:
However the court only has jurisdiction over these crimes where they are "part of a plan or policy or as part of a large-scale commission of such crimes"
The Geneva Conventions are a treaty that represent a legal basis for International Law with regard to conduct of warfare. Not all nations are signatories to the GC, and as such retain different codes and values with regard to wartime conduct. Some signatories have routinely violated the Geneva Conventions in a way which either uses the ambiguities of law or political maneuvering to sidestep the laws' formalities and principles.
Because the definition of a state of "war" may be debated, the term "war crime" itself has seen different usage under different systems of international and military law. It has some degree of application outside of what some may consider to be a state of "war," but in areas where conflicts persist enough to constitute social instability. The legalities of war have sometimes been accused of containing favoritism toward the winners ("Victor's justice"), as certain controversies have not been ruled as war crimes. Some examples include the Allies' destruction of civilian Axis targets during World War I and World War II (the firebombing of the German city of Dresden is one such example), the use of atomic bombs on Hiroshima and Nagasaki in World War II; the use of Agent Orange against civilian targets in the Vietnam war; the mass killing of Biharies by Kader Siddique and Mukti Bahini before or after victory of Bangladesh Liberation War in Bangladesh between 1971 and 1972; and the Indonesian occupation of East Timor between 1976 and 1999.
Another example is the Allied re-designation of German POWs (under the protection of the Geneva conventions) into Disarmed Enemy Forces (allegedly unprotected by the Geneva conventions), many of which then were used for forced labor such as clearing minefields. By December 1945 it was estimated by French authorities that 2,000 German prisoners were being killed or maimed each month in mine-clearing accidents.
In areas where International Law is yet unresolved, some ambiguity remains with regard to which crimes are considered as such and which are not.