Its mobile killing units were active in the implementation of the Final Solution in the territories overrun by the Nazi war machine.[66] This SD subsidiary worked closely with the Wehrmacht in persecuting Jews, communists, partisans, and other groups, as well.[lower-alpha 4] Starting with the invasion of Poland throughout the campaign in the East, the Einsatzgruppen ruthlessly killed anyone suspected of being an opponent of the regime, either real or imagined.[lower-alpha 5] The men of the Einsatzgruppen were recruited from the SD, Gestapo, Kripo, Orpo, and Waffen-SS.[69]