In December 1941, Adolf Hitler threw a Christmas Party for his fellow Nazis. It was a lavish affair, in which the Nazi Party's top officials, statesmen, and generals gathered before a massive Christmas tree to feast and exchange presents with hundreds of jackbooted S.S. cadets in attendance. In surviving pictures taken by the Führer's own personal photographer, Hitler appears somewhat dour and maybe a little sad to be at this event, as if he feels out of place despite his importance, and no wonder: What holiday could be less suited to the sentiments of that genocidal, warmongering dictator than...