Following the brutal invasion and occupation of Poland, the Nazis moved swiftly to realize one of their key ideological aims, the expansion of German living space: deport Jews, bring in German settlers and subjugate the rest of the population to a selection process to separate Poles from ethnic Germans. As simple as this might have seemed initially, the various parts of the German occupation machinery soon found themselves embroiled in a bitter fight about the essence of Germanness and how to identify a German. Gerhard Wolf reveals an astonishing development in which a more inclusivist understanding of Germanness based on a more traditional notion of Volk eventually won out against one that was based on Rasse and much more exclusivist. This had important implications, as Wolf can show, as it paved the way for turning around three million Poles into German citizens. Parallel to the mass deportation and mass murder of Christian Poles and the genocide of Jewish Poles, the Nazis paradoxically thus also presided over the largest (forced) assimilation program in German history. Students and scholars of the Polish occupation, the Holocaust, and Nazism will find new analysis of German imperialism, ethnic cleansing, and genocide in this important book.