The crime of aggression was prosecuted before the Nuremberg and Tokyo Tribunals after World War II. But there was inadequate agreement among states to include aggression as an operational crime in the Statute of the International Criminal Court (ICC) during the 1996–98 negotiations. Only during a review conference in Kampala in 2010 was a definition agreed. The activation of the amendments to the ICC Statute on aggression is expected in the near future. This represents a highly significant development of international criminal justice. The CUP volumes are edited by the two leading actors during the 2010 negotiations in Kampala, who represented Germany and Liechtenstein respectively. Germany has led the work to operationalize the crime of aggression. The contributors to the volumes include other international lawyers who played key roles in the making of the 2010 amendments. There are 53 chapters, organized in five parts: I. History, II. Theory, III. Crime of Aggression Under Current International Law, IV. Crime of Aggression and National Law, and V. Crime of Aggression and the Future World Order. Part III corresponds to what we normally think of as a legal commentary. Together, the parts amount to a comprehensive anthology on the illegal use of force between states. Given the fundamental importance of the topic of the crime of aggression for the international legal order as a whole, and the leading expertise of the editors and many of the authors, the volumes are indispensable to international lawyers and international relations experts alike. I hope they will not be dissuaded by the exorbitant price of USD 350 set by the publisher.