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 new six part landmark history series.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, in order to tell a 'Behind Closed Doors' history. It's a new way on television of looking at this most vital period, and will change the way you think about the war.This fifth episode focuses on the dramatic story of the Red Army's fight through Eastern Europe in 1944, as well as the behind the scenes history of the most famous Allied conference of the war at Yalta in the Crimea.