As Germany observes the anniversary of the Wannsee Conference, witnesses of the Nazi era are dying and antisemitism is resurgent in Europe and the United States. BERLIN — On Jan. 20, 1942, 15 high-ranking officials of the Nazi bureaucracy met in a villa on Lake Wannsee on the western edge of Berlin. Nibbles were served and washed down with cognac. There was only one point on the agenda: “The organizational, logistical and material steps for a final solution of the Jewish question in Europe.” Planning the Holocaust took all of 90 minutes. Eighty years after the infamous Wannsee Conference that...