By May 1941, Germany had established effective control over mainland Europe. As you can see from the map that accompanies this article, the only mainland countries not occupied by German or Italian forces were neutral countries, like Spain, Portugal, Sweden Turkey and Switzerland and, to the East, the Soviet Union.

To the West, Great Britain stood against Germany. A threat, certainly, but its offensive capabilities were limited and, after Dunkirk, a British invasion of mainland Europe was inconceivable. Further to the West, the pre-Pearl Harbour United States had, of course, not yet entered the war. But an invasion of Great Britain may well have dragged it prematurely into the conflict. This, combined with Britain’s strong defensive position – it was, after all, on an island – would have made the planned Operation Sealion invasion seem like a risky prospect.

Instead, to the East, stood the Soviet Union. The Soviet Union signed a nonaggression pact in 1939 with Germany and was nominally its ally. The USSR was known to be fast building up its military strength, after a paranoid Stalin had initially purged his officer corps. Although, for the moment, the USSR seemed militarily weaker than Germany, it was clear that Germany’s strategic advantage could not last forever.

Added to this, the Soviet Union was a massive source of the natural resources that Germany so badly needed if it was to consolidate its hold over Europe and to continue its rapid military expansion. Oil from the Caucasus, food from the breadbasket of Ukraine and labour from across a defeated Soviet Union would combine to leave Germany in an unassailable global position of power.

One also cannot overlook the racial dimension of Hitler’s decision to invade the Soviet Union. The Slavs of Eastern Europe and the Soviet Union were regarded by Hitler as being Untermensch, whose land should be taken from them in order to provide the German people with Lebensraum. This may well have blinded Hitler to some of the larger strategic considerations (and, indeed, many within the German leadership argued against an invasion, fearing that it would be a drain on German resources).

Had the invasion of the Soviet Union succeeded, Hitler’s Germany would have found itself in a strong position to either invade Great Britain at its leisure, or to have made peace with an isolated island on very favourable terms. Instead, of course, Operation Barbarossa failed and the German military found itself bogged down in the vast Soviet Union. Once the United States had joined the war and Great Britain had regained an offensive capability, Germany found itself sandwiched between two very strong enemies who gradually squeezed the Third Reich until its defeat was assured.