This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book focuses on crimes that were committed under international humanitarian law, previously known as the laws of war. The four Geneva Conventions and their additional Protocols, as well as the Hague Conventions, are the most well-known treaties which cover humanitarian law. The book examines both the political realities of these institutions as their legal and judicial underpinnings. It explores how the political compromise which established these tribunals impacted the delivery of justice for victims and the rights of the accused. It talks about the international community, states, victims and defendants. The book provides some core definitions of the various subfields of international law to place the tribunals within a general legal framework. It shows how history should judge the role of the Nuremberg and the Tokyo tribunals in codifying international humanitarian law and providing a judicial mechanism for justice.