The introduction sketches the scope and nature of Allied internment and outlines the key questions that internment raises. It situates internment within the history and historiography of postwar Germany and the broader study of the history of camps. It shows that internment, especially by the western powers, has often been overlooked. Even studies of post-Nazi transitional justice often neglect it, focusing instead on trials of Nazi and war criminals and on professional and civil sanctions against Nazi Party members and fellow travellers. The introduction argues that including internment reveals post-Nazi transitional justice to have been more severe than has long been believed and that Allied measures did not rest on undifferentiated accusations of German collective guilt, but on a more nuanced approach. The introduction identifies multiple meanings of terms such as ‘denazification’ that are crucial for understanding internment. It also discusses the existing literature on internment and the controversial question of the comparability of the Soviet and western cases. It argues that comparison is legitimate and that black-and-white depictions of brutal, arbitrary Soviets and fair, friendly westerners oversimplify a more complex reality. Finally, the introduction outlines the book’s structure, sources, and scope, which includes some comparison with Austria.