This book explores the confrontation of radically assimilated Jews with the violent collapse of their envisioned integration into a cosmopolitan European society, which culminated during the Holocaust. This confrontation is examined through the biography of the German-speaking intellectual and prominent communist theoretician of the Jewish question Otto Heller (1897-1945), focusing on the tension between his Jewish origins and his universalistic political convictions. Radical Assimilation in the Face of the Holocaust traces the development of HellerE s position on the Jewish question in three phases: how he grew up to become a typical Central European "non-Jewish Jew" (1897-1931); how he became exceptional in that category by focusing his intellectual work on the Jewish question (1931-1939); and how he reacted to the persecution and murder of European Jewry as a member of the Resistance in occupied France and in Auschwitz (1939-1945). Breaking with the common portrayal of Heller as a self-hating Jew, Tom Navon argues instead that Heller came to lay the foundations for the groundbreaking recognition by communists of worldwide Jewish national solidarity.