A war crime is a crime which is committed during the course of a war, either by a civilian or a member of the military. War crimes have been a problem throughout human history, although prosecution of such crimes only really emerged in the 20th century, thanks to general public outrage about crimes committed by German and Japanese forces during the Second World War. Unfortunately, this term can be a bit challenging to define, as it is somewhat nebulous. War crimes are also notoriously hard to prosecute and prove.
Most governments agree that any action which violates international conventions and agreements about warfare is a war crime. For example, abuse of prisoners of war is outlawed by the Geneva Convention, and therefore considered a war crime. Perfidy, the act of willfully deceiving the enemy, is also a war crime. Crimes against humanity such as torture, genocide, mass deportation, and other acts of persecution are also considered war crimes when they occur during a period of war.
Ideally, individual nations should prosecute their own war criminals, and in several countries, tribunals have been established after periods of war to acquit or convict and sentence suspected war criminals. In other instances, neutral courts such as those in the Hague have tried war criminals after a period of war. Trials typically include testimony from victims, if possible, along with witnesses and professionals such as forensic anthropologists who analyze evidence at suspected sites of criminal activity. Sentences for war crimes vary, depending on the magnitude of the crime and the will of the court.
The first serious attempts to prosecute war criminals occurred after the First World War, and they were largely considered a failure. After the Second World War, however, a tribunal was arranged in Buremburg, Germany, for the purpose of trying suspected war criminals. The tribunal was run by the Allied occupying forces, and a number of prominent Nazis were tried during the Nuremberg trials, including Hermann Göring and Rudolf Hess. This tribunal set the stage for future prosecutions of suspected war criminals, and caused a shift in international attitudes about the concept of war crime.
Internationally, organizations such as the UN may monitor conflict zones for signs of war crimes. In some cases, suspected war criminals may be remanded to a neutral court such as the International Criminal Court in the Hague, if the United Nations feels that they will not be tried appropriately in their home nations. This international court has very specifically spelled out authorities, to ensure that its power is not abused.