Streim postulated that the existence of an early comprehensive order was a fabrication created for use in Ohlendorf's defence. This theory is now widely accepted by historians. Longerich notes that most orders received by the "Einsatzgruppen" leaders—especially when they were being ordered to carry out criminal activities—were vague, and couched in terminology that had a specific meaning for members of the regime. Leaders were given briefings about the need to be "severe" and "firm"; all Jews were to be viewed as potential enemies that had to be dealt with ruthlessly. British historian Sir Ian Kershaw argues that Hitler's apocalyptic remarks before Barbarossa about the necessity for a war without mercy to "annihilate" the forces of "Judeo-Bolshevism" were interpreted by "Einsatzgruppen" commanders as permission and encouragement to engage in extreme antisemitic violence, with each "Einsatzgruppen" commander to use his own discretion about how far he was prepared to go.