LAURENCE REES: So then Hitler does a deal with Stalin in the summer of 1939 - is it your understanding that that was only ever intended, as far as he was concerned, to be temporary?

RICHARD EVANS: The Hitler/Stalin pact was exactly like the non-aggression agreement with Poland in 1934, it was a tactical measure designed to buy time. Hitler intended in the summer of 1939 to invade Poland and he did not want the Russians coming in the other side and creating objections and maybe fighting against him. So he did a deal with Stalin initially in order to give him the leeway to move into Poland and to make sure the Russians didn’t intervene.

LAURENCE REES: But is this just a temporary measure or is it something that could have existed for the long term if things had gone differently?

RICHARD EVANS: The core of Hitler’s foreign policy aim was to invade and conquer eastern Europe and to expel or eliminate the vast majority of the Slavs that lived there, and to recreate it as an of equivalent of the American west - a kind of bread basket for Germany- somewhere with resources. Industrial resources and agricultural resources would make Germany into a world power, capable of standing head to head with America in the longer run. Part of the reason for Hitler increasing the pace of his foreign policy aggression in 1938/39 was a feeling that he himself had limited time to run, that his health might not hold out, that he might in fact die at some point in the not too distant future.

So from initially thinking of a war of conquest in 1942/43 he moved this forward to 1939. In addition to that, the Battle of Britain and his failure to defeat Britain played a role - he realised of course that he was fighting not just Britain but the British Empire, increasingly backed by America. It has never been true that Britain stood alone, Britain had the whole Empire behind it. This was a major world Empire, the largest at the time in the late 1930s. Hitler desperately wanted to make peace with Britain and he thought that invading and conquering the Soviet Union would eliminate Britain’s last ally on the continent and force it to the negotiating table. So there’s both a long-term strategy there and a short-term strategy. The long-term tactic of conquering the western part of the Soviet Union and turning it into a German reserve of materials and the short-term tactic of bringing Britain to the negotiating table.

LAURENCE REES: Isn’t it a monumental misreading and misjudgment on Hitler’s part? After all Britain’s only way of carrying on the war was with American not Soviet help? How could it be rational to think that the way forward was to defeat Britain by invading the Soviet Union?

RICHARD EVANS: Well, it’s also because he thought that you needed to conquer the western part of the Soviet Union and get all these resources and then be able to say to Britain, look, we totally dominate the European continent, we have all this massive power behind us and you can’t possibly hold out now, we’re the equal of America in power, political, economic resource terms.