On Sept. 1, 1939, one week after Nazi Germany and the Soviet Union signed a non-aggression pact, more than a million German troops—along with 50,000 Slovakian soldiers—invaded Poland. Two weeks later, ...

In the late 1930s and early 1940s, a German photographer and ardent Nazi named Hugo Jaeger enjoyed unprecedented access to the Third Reich’s upper echelon, traveling with Adolf Hitler to massive ...