My book project presents the first full-length biography of one of the major scientific figures of the twentieth century, physicist Pascual Jordan. While his contributions to physics were crucial to our understanding of the field today, Jordan is also remembered for his decision to join the Nazi Party in 1933. Using previously unknown archival sources, my project describes Jordan’s associations with far-right groups prior to Hitler’s seizure of power, his negotiations and machinations with various power centers in the Nazi state after 1933 and during World War II, as well as his political and pedagogical aims in postwar West Germany. Devoting special attention to how he is remembered in historical memory, my work shows how Jordan’s reputation as a remorseless Nazi was shaped by his actions during the early Cold War.