The attack came as a complete surprise to the leader of the Soviet Union, Joseph Stalin. Despite repeated intelligence warnings, which included the precise day and hour of Germany's incipient assault, Stalin remained convinced that Hitler would not risk an eastern war as long as the British Empire remained undefeated. It has been argued that Stalin in fact planned a pre-emptive attack on Germany for the early summer of 1941, and was then thrown off-balance by the German invasion.' For two years Soviet forces pushed the German army back into Germany... .' The evidence makes clear the defensive posture of the Soviet Union in 1941. Stalin did not want to risk war, though he hoped to profit from the German-British struggle if he could. In the event, the shock of attack almost unhinged the Soviet state, and by the autumn German forces had destroyed most of the Red Army and the Russian air force, surrounded and besieged Leningrad - where over one million people died of starvation and cold - and were approaching the outskirts of Moscow.

The Red Army had sufficient reserves to stop the German army from completing the rout in December 1941, but the following summer German offensives launched far to the south of Moscow, to seize the rich oilfields of the Caucasus and to cut the Volga shipping route, created further chaos. Hitler hoped that German forces would capture the oil and sweep on through the Middle East to meet up with Axis forces in Egypt. The Volga was to be blocked at Stalingrad, after which German forces could wheel northwards to outflank Moscow and the Soviet line. The southern attack failed at Stalingrad. After weeks of chaotic retreats and easy German victories, the Red Army solidified its defence and against all the odds clung on to the battered city. In November 1942 Operation Uranus was launched by the Soviets, and the German Sixth Army at Stalingrad was encircled.

Some historians have seen this as the turning point of the war. But not until the Red Army had decisively defeated German forces in the more favourable summer weather of 1943 did the tide really turn. The Battle of Kursk in July 1943 was one of the greatest set-piece battles in military history. The Red Army withstood a massive German assault, and then counter-attacked. For two years Soviet forces pushed the German army back into Germany, until in May 1945 Soviet forces accepted the surrender of the relic of Hitler's army in Berlin.