 Browning argues that sometime in mid-July 1941 Hitler made the decision to begin general genocide owing to his exhilaration over his victories over the Red Army, whereas Burrin contends that the decision was made in late August 1941 owing to Hitler's frustration over the slowing down of the Wehrmacht.Kershaw argues that the dramatic expansion in both the range of victims and the intensity of the killings after mid-August 1941 indicates that Hitler issued an order to that effect, most probably a verbal order conveyed to the "Einsatzgruppen" commanders through either Himmler or Heydrich.Joachim Fest (1926-2006) was a German historian who wrote a biography of Hitler, "Hitler