LAURENCE REES: What is the biggest single mistake of greatest consequence that any individual made in that war?

SIR IAN KERSHAW: Well I’d say, unquestionably, Hitler’s decision to invade the Soviet Union. A decision which he thought was, obviously, a sound one. That Germany would actually win that war. But by the late summer of 1941, by the time you’re into August and September, already the blitzkrieg assault is failing, it’s not going to be over by the winter and, of course, by the time it’s stretched out into a long war in the Soviet Union then the results are as we know them to have been – colossal losses on both sides, particularly even on the Soviet side; but ultimately then a war which is draining Germany of manpower and resources, which they can’t in the end win. So I think that was the most dramatic mistake that was made.