A crime of aggression or crime against peace is the planning, initiation, or execution of a large-scale and serious act of aggression using state military force. The definition and scope of the crime is controversial. The Rome Statute contains an exhaustive list of acts of aggression that can give rise to individual criminal responsibility, which include invasion, military occupation, annexation by the use of force, bombardment, and military blockade of ports. In general, committing an act of aggression is a leadership crime that can only be committed by those with the power to shape a state's policy of aggression, as opposed to those who discharge it.
The philosophical basis for the wrongness of aggression is found in just war theory, in which waging a war without a just cause for self-defense is unjust. In the wake of the German invasion of the Soviet Union during World War II, Soviet jurist Aron Trainin made the first successful proposal to criminalize aggression. The Charter of the International Military Tribunal provided criminal liability for waging aggressive war, which was the main focus of the Nuremberg trial. Other participants in World War II were tried for aggression in Finland, Poland, China, the subsequent Nuremberg trials, and the Tokyo trial. No one has been prosecuted for aggression either before or since the 1940s.
