The SS Einsatzgruppen were the most notorious of the Schutzstaffel (SS), the paramilitary death squads of Nazi Germany. Under the leadership of the notorious Otto Ohlendorf they were responsible for the introduction of a regime of terror involving mass killings, primarily by shooting, in occupied territory of the Soviet Union during 1941 and 1942. Under the direction of Reichsführer-SS Heinrich Himmler and the direct supervision of SS-Obergruppenführer Reinhard Heydrich the Einsatzgruppen played the leading role in the implementation of the Final Solution in territories conquered by Nazi Germany, but they were also responsible for combatting partisans and eliminating Soviet political commissars, mental patients and Gypsies throughout Eastern Europe.