LAURENCE REES: And so Hitler invades the Soviet Union, and then there’s this question about the extent to which Stalin essentially cracks up in those early days. What’s your take on that?

ROBERT SERVICE: Well, there is a story that Stalin had a nervous breakdown and had to be cosseted out of it by the rest of the party politburo, but if you look at his address book for the days immediately after the beginning of Operation Barbarossa, in fact he’s out of the loop only for a day or two, and he’s active all the rest of the time. It would have been astonishing if he hadn’t felt a certain attack of demoralisation because he’d messed everything up. I think he really had a juddering shock applied to him but he managed to survive it and get through it and to manipulate his moments of weakness to good effect.

He waited until the politburo came out to his dacha to persuade him to take full control of the war effort and even at that moment, in other words, even at the lowest point of his morale, he knew how to handle his politburo comrades and to keep them at a level much lower than he occupied. So I don’t accept this story that he had a nervous collapse.

LAURENCE REES: Some say that when the politburo went to see him he believed he was going to be arrested. You don’t think he believed that at all?

ROBERT SERVICE: I think there is something in the banter between them, 'I thought you were coming out to arrest me”: but that’s not evidence that that’s what he really thought. I don’t think that he was quite so mentally shattered. He was shaken, but he wasn’t shattered by his terrible decision to ignore all of the intelligence reports that the Germans were going to invade the USSR.

LAURENCE REES: And why do the Red Army - generally speaking - perform so badly in the summer of 1941?

ROBERT SERVICE: Well, the Soviet military doctrine was bizarre because it was based on the idea that no invasion would be effective, and that therefore no great defence works had to be put in hand, even after the Sovietisation of Latvia, Lithuania and Estonia. There was no great hurry about that because the war would be fought on the territory of the enemy, and so all preparations were made on that basis. Together with the fact that the Red Army wasn’t allowed to respond actively to the first battles in which it was engaged, this was disastrous for the Soviet Union. So for the first few weeks the Red Army was made vulnerable by doctrine and by lack of preparations and by distrust on the part of Stalin for the commanders. But as soon as the line is held, then the vast human and industrial resources of the Soviet Union were bound to prove themselves superior to those of the Third Reich, so long as the Soviet Union was effectively led. And brutal as he was as a dictator and as a military commander, Stalin knew how to lead the defence of his country.

LAURENCE REES: How close do you think the Soviet Union came to defeat in October 1941?

ROBERT SERVICE: I think that if Hitler had begun his offensive in May or perhaps April then the Soviet Union might well have gone under. It was saved by the lateness of the invasion. By October there wasn’t snow but there was plenty of mud, and mud is a really damaging thing for equipment such as the Germans had. We always think about the snow of the winter but the mud of the autumn was just as important. October was too late. If Hitler hadn’t already taken the two great centres of the Soviet Union, Moscow and Leningrad, then he didn’t stand quite the chance of victory that he’d assumed would be easy.

LAURENCE REES: And how crucial was it that Stalin decided to stay in Moscow in October and not run?

ROBERT SERVICE: I think it was, from the point of view of morale, very important that Stalin stayed on in Moscow, and he was tempted to move off to the Volga region for security, but at the last moment he changed his mind. He appreciated that if it was known that the leader was staying in Moscow within bombing range of the German armed forces then the morale of the Soviet defence effort would be all the greater.