Though General Halder did not record any mention of Jews, German historian Andreas Hillgruber argued that because of Hitler's frequent contemporary statements about the coming war of annihilation against "Judeo-Bolshevism", his generals would have understood Hitler's call for the destruction of the Soviet Union as also comprising a call for the destruction of its Jewish population.[35] The genocide was often described using euphemisms such as "special tasks" and "executive measures"; Einsatzgruppe victims were often described as having been shot while trying to escape.[36] In May 1941, Heydrich verbally passed on the order to kill the Soviet Jews to the SiPo NCO School in Pretzsch, where the commanders of the reorganised Einsatzgruppen were being trained for Operation Barbarossa.[37] In spring 1941, Heydrich and the First Quartermaster of the Wehrmacht Heer, General Eduard Wagner, successfully completed negotiations for co-operation between the Einsatzgruppen and the German Army to allow the implementation of the "special tasks".[38] Following the Heydrich-Wagner agreement on 28 April 1941, Field Marshal Walther von Brauchitsch ordered that when Operation Barbarossa began, all German Army commanders were to immediately identify and register all Jews in occupied areas in the Soviet Union, and fully co-operate with the Einsatzgruppen.[39]