The Nuremberg Charter introduced the crime of aggression into international law. The American Chief Prosecutor Robert Jackson gave a famous promise that offenders who commit acts of aggression shall be prosecuted and international criminal law would be applied against them. Notwithstanding the efforts of the United Nations to criminalize aggression, in the period between the Nuremberg trial and the Kampala Conference in 2010 there has not been a universally accepted definition of aggression. Even though the Nuremberg Principles had been recognized and the Tokyo judgment followed the Nuremberg precedent, a universally accepted definition of the ‘supreme crime’ was missing for more than 60 years. One could argue that the Cold War was the main reason for the absence of international follow-up to the criminalization of aggression after 1947; or one may also say that the international community relied on the UN Charter provisions as a trustworthy bulwark against acts of aggression. The definition of ‘act of aggression’ from 1974 could not be labeled as ‘historic’ simply because in reality nothing truly changed. The international tribunals prior to the establishment of the International Criminal Court did not have the crime of aggression in their statutes. In this article the author describes the development of the ‘supreme crime’ specifically after the Nuremberg trial, with a focus on the UN efforts in dealing with acts of aggression. Individual responsibility for the crime of aggression as such is also examined in this ‘vacuum period’ where the international consensus was missing.