For Operation Barbarossa (June 1941), initially four Einsatzgruppen were created, each numbering 500–990 men to comprise a total force of 3,000.[5] Each unit was attached to an army group: Einsatzgruppe A to Army Group North; Einsatzgruppe B to Army Group Center, Einsatzgruppe C to Army Group South, and Einsatzgruppe D to the 11th German Army.