In Nolte's view, Nazi anti-communism was "understandable and up to a certain point, justified". For Nolte, the "racial genocide" as he calls the Holocaust was a "punishment and preventive measure" on the part of the Germans for the "class genocide" of the Bolsheviks. American historian Peter Baldwin noted parallels between Nolte's views and those of American Marxist historian Arno J. Mayer:. Both Nolte and Mayer perceive the interwar period as one of intense ideological conflict between the forces of the Right and Left, positing World War II as the culmination of this conflict, with the Holocaust a byproduct of the German-Soviet war. Baldwin distinguished Nolte from Mayer in that Nolte considered the Soviets aggressors who essentially got what they deserved in the form of Operation Barbarossa, whereas Mayer considered the Soviets to be victims of German aggression. Operation Barbarossa, in Nolte's thinking, was a "preventive war" forced on Hitler by an alleged impending Soviet attack. Nolte wrote that Hitler's view of the Russian people as barbarians was an "exaggeration of an insight which was basically right in its essence" and that Hitler "understood the invasion of the Soviet Union as a preventive war" as the Soviet desire to bring Communism to the entire world "must be seen as mental acts of war, and one may even ask whether a completely isolated and heavily armed country did not constitute a dangerous threat to its neighbors on these grounds alone".