Joseph Stalin was a tyrant responsible for the death of millions - yet he was also a vital ally of Britain and America during the Second World War.How was it possible for Churchill and Roosevelt to deal with one tyrant, Joseph Stalin, in order to help beat another - Adolf Hitler? That s one of the key questions at the heart of this six-part landmark history series for BBC2.The series uses dramatic reconstructions based on extensive fresh research in Russian and Western archives, and extraordinary testimony from witnesses of the time, including former Soviet secret policemen who have not spoken before on camera - This second episode focuses on the secret history of Stalin s dealings with Churchill and the West in the wake of the German invasion of the Soviet Union.