Historical research is not a neutral exercise, but it often answers current political questions and the self-definition of society. Lost wars always generate a special necessity to deal with the motivations of the actors, and the nonsense of mass slaughter. After both World Wars the debate among German historians was influenced by the publication of documents and the discussions on the German guilt for mass destruction, atrocities and after 1945 for Holocaust and genocide. The establishment Western German military historians created and developed a critical military historiography against apologetic writings and army commanders’ memoirs. A political interpretation of World War II as a consequence of Hitler’s war aims and of the Nazi aggressive war strategy created an important basis for Western German society. Military historians rarely dealt with the German occupation policies which became instead a favourite topic for academic research at Universities and Institutes such as the Munich Institut für Zeitgeschichte. After 1989 a major internationalization of research led to a criticism of the Western German military and political historical approach on WW II. This called for a new perspective especially on German perpetrators and bystanders, capable of dealing with the detailed description of the implementation of the Holocaust and of mass slaughter in anti-partisan war and in extermination camps.