LAURENCE REES: What was the most consequential mistake anybody made in the conflict?

OMER BARTOV: The invasion of the Soviet Union. Because once Hitler invaded the Soviet Union he might have won, of course, it’s not impossible, but it also ultimately was the end of his regime. And had he not invaded the Soviet Union, which I’ve always believed was not possible for him not to do, but had he not done that, had he been something else, a militaristic kind of regime might have still existed in Central Europe. Having invaded the Soviet Union and having failed in the first few months to destroy it, that was the end of Nazi Germany.

LAURENCE REES: And you’re not of the view that Stalin was always going to at some point turn on the Nazis?

OMER BARTOV: It’s always possible, but there’s no proof that he ever wanted to do it or that he was preparing for it. You don’t prepare to attack a country like Germany by destroying your entire officer corps, which is exactly what he did on the eve of World War Two, including the best armoured corps general that the Soviet Union had, Tukhachevski. And again, not because he was a nice man, not because he did not have any plans to expand, but there was no immediate plan to attack Germany.