Joining Hitler's Crusade: European Nations and the Invasion of the Soviet Union, 1941

The reasons behind Hitler's invasion of the Soviet Union are well known, but what about those of the other Axis and non-Axis powers that joined Operation Barbarossa? Six other European armies fought with the Wehrmacht in 1941 and six more countries sent volunteers, as well as there being countless collaborators in the east of various nationalities who were willing to work with the Germans in 1941. The political, social and military context behind why so many nations and groups of volunteers...