Dust off the Nuremberg Files:

The Nuremberg Trial Counts One & Two: Conspiracy to Wage Aggressive War and Waging Aggressive War. The "common plan or conspiracy" charge was designed to get around the problem of how to deal with crimes committed before the war. The defendants charged under Count One were accused of agreeing to commit crimes. Accusation for Count Two was defined in the indictment as "the planning, preparation, initiation, and waging of wars of aggression, which were also wars in violation of international treaties, agreements, and assurances."