From Wishing the War Away:
Stalin was planning a preemptive strike against Germany but thought he had at least a year’s time because he could not bring himself to believe that Hitler would attack the Soviet Union before Britain had fallen. ‘Hitler and his generals are not so foolish as to start a two-front war,’ he said. ‘The Germans broke their neck on this in World War I. Hitler would never risk such a thing.’Stalin’s reasoning was intelligent, rooted in history and completely wrong.