The Einsatzgruppen and the Holocaust by Bullets, 1941

The Einsatzgruppen were SS mobile killing units formed to operate directly in the wake of the advancing Wehrmacht. Four major operational groups, designated A, B, C, and D, were deployed following the launch of Operation Barbarossa, the German invasion of the Soviet Union, in June 1941, systematically executing entire Jewish communities in occupied Soviet territory by mass shooting, assisted by regular German police units and by local collaborators. Victims were typically shot into mass graves, often dug by the victims themselves beforehand, and the massacres also extended to Soviet political commissars, to Roma, and to other groups the Nazi regime deemed enemies.