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".
Similar concepts, 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.
International Criminal Court
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:
- Grave breaches of the Geneva Conventions, such as:
- Willful killing, or causing great suffering or serious injury to body or health
- Torture or inhumane treatment
- Unlawful wanton destruction or appropriation of property
- Forcing a prisoner of war to serve in the forces of a hostile power
- Depriving a prisoner of war of a fair trial
- Unlawful deportation, confinement or transfer
- Taking hostages
- The following acts as part of an international conflict:
- Directing attacks against civilians
- Directing attacks against humanitarian workers or UN peacekeepers
- Killing a surrendered combatant
- Misusing a flag of truce
- Settlement of occupied territory
- Deportation of inhabitants of occupied territory
- Using poison weapons
- Using civilians as shields
- Using child soldiers
- The following acts as part of a non-international conflict:
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" 
- Heads of state & government
- President of Nazi Germany Großadmiral Karl Dönitz and Prime Minister General Hideki Tojo of the Empire of Japan in the aftermath of World War II.
- Former Yugoslav President Slobodan Milošević was brought to trial for war crimes and genocide, but died in custody on March 11, 2006, before the trial could be concluded.
- Former Liberian President Charles G. Taylor was also brought to the Hague charged with war crimes; his trial was provisionally scheduled to begin in April 2007, but was postponed until June 2007 to allow the defense more time to prepare, and is now ongoing.
- Former Bosnian Serb President Radovan Karadzic was arrested in Belgrade on 18 July 2008 and brought before Belgrade’s War Crimes Court a few days after. He was extradited to the Netherlands, and is currently in The Hague, in the custody of the International Criminal Tribunal for the former Yugoslavia. He has not yet entered a plea; his next appearance is scheduled for 29 August 2008.
- Other prominent indictees
- Hermann Göring - Reichsmarschall, Commander in Chief of the Luftwaffe (German Air Force) and designated successor to Adolf Hitler (until 1945)
- Ernst Kaltenbrunner - highest ranking SS leader to face trial.
- Adolf Eichmann - senior member of the SS and the "the architect of the Holocaust"
- Wilhelm Keitel - Generalfeldmarschall, head of the Oberkommando der Wehrmacht (High Command of the Armed Forces)
- Erich Raeder - Großadmiral, Commander in Chief of the Kriegsmarine from 1928 until his retirement in 1943
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.
Historically, the punishment for committing war crimes was capital punishment, but in many cases, war criminals were sent to national prisons to live out the rest of their lives. At the modern international tribunals, capital punishment is banned, and conviction results in a sentence for a term of years. The convicted person serves his or her sentence in a national prison system, whose country has agreed with the tribunal to effect execution of sentence.