The Einsatzgruppe for Special Purposes operated in eastern Poland starting in July 1941.[160] The historian Richard Rhodes describes them as being "outside the bounds of morality"; they were "judge, jury and executioner all in one", with the authority to kill anyone at their discretion.[161] Following Operation Barbarossa, these Einsatzgruppen units, together with the Waffen-SS and Order Police as well as with assistance from the Wehrmacht, engaged in the mass killing of the Jewish population in occupied eastern Poland and the Soviet Union.[161][162][163] The greatest extent of Einsatzgruppen action occurred in 1941 and 1942 in Ukraine and Russia.[164] Before the invasion there were five million registered Jews throughout the Soviet Union, with three million of those residing in the territories occupied by the Germans; by the time the war ended, over two million of these had been murdered.[165]