World War II was fought on a scale unlike anything before or since in human history, and the unfathomable casualty counts are attributable in large measure to the carnage inflicted between Nazi Germany and the Soviet Union during Hitler’s invasion of Russia and Stalin’s desperate defense. The invasion came in 1941 following a nonaggression pact signed between the two in 1939, which allowed Hitler to focus his attention on the west without having to worry about an attack from the eastern front.