The unlikely non-aggression pact between Hitler and Stalin that existed until the Nazis betrayed the Soviet Union in June 1941, when Stalin looked to form a new alliance.

A look at the events of 1941 when, having been betrayed by Hitler, Stalin switched his allegiances to Britain and America. It was an alliance based on military pragmatism, which never altered the mutual antipathy between Churchill - who despised only Nazism above Communism - and the Soviet leader, who knew that his Red Army was ill-equipped to cope with the Nazi onslaught alone.

The relationship between Churchill and Stalin, and the secret history that clouded their first meeting in Moscow in August 1942 where they became set on a path to achieve an uncomfortable alliance.

The secret history of the Second World War by focusing on the first meeting of the "Big Three" - Churchill, Roosevelt and Stalin - which took place in Tehran in 1943.

Features the Red Army's progress through eastern Europe in 1944, as well as uncovering the power struggles and political intrigue going on behind the scenes during the most famous Allied conference of the conflict, held at Yalta in the Crimea.