This guide to the crime of aggression provisions under the Rome Statute of the International Criminal Court (ICC) offers an exhaustive and sophisticated legal analysis of the crime's definition, as well as the jurisdictional provisions governing the ICC's exercise of jurisdiction over the crime. A range of practical issues likely to arise in prosecutions of the crime of aggression before the ICC are canvassed, as is the issue of the domestic prosecution of the crime. It also offers an insight into the geopolitical significance of the crime of aggression and the activation of the ICC's ability to exercise its jurisdiction over the crime. The author's intimate involvement in the crime's negotiations, combined with extensive scholarly reflection on the criminalisation of inter-State uses of armed force, makes this highly relevant to all academics and practitioners interested in the crime of aggression.