Biographer Alan Bullock avows Hitler "laid great stress" on the need to concentrate on a single enemy, an enemy he lumps together as "Marxism and the Jew". Shortly in the wake of the Commissar Order, a directive pursuant to the German invasion of the Soviet Union, SS Deputy Reinhard Heydrich informed the SS of Hitler's geopolitical philosophy which conflated Bolshevism and Jews, writing that "eastern Jewry is the intellectual reservoir of Bolshevism and in the Führer's view must therefore be annihilated". Considering the eventual Nazi invasion of the Soviet Union (Operation Barbarossa), no additional inducements are really requisite concerning Hitler's hatred of communism, particularly since the Nazi persecution and extermination of these groups was not only systematic, but it was extensive both within Germany and only intensified in the occupied zones during the war under Hitler's leadership.