Joseph Stalin's wartime diplomacy sits at the center of this series, drawn from Soviet archives that opened only after the USSR's collapse. British historian Laurence Rees leads the research and writing, pairing documentary interviews with dramatic reenactments in which actors play Stalin, Churchill, Roosevelt, and Hitler. The film reconstructs the private conversations and secret meetings behind the public alliance, including the horse-trading at Tehran and Yalta where the three Allied leaders carved up postwar Europe while still fighting the war. It tracks how Stalin managed Churchill's suspicion and Roosevelt's trust differently, extracting concessions from each, and how the earlier Nazi-Soviet pact and its collapse shaped his calculations toward Hitler. Newly available archival material grounds claims about troop movements, territorial deals, and the personal rapport Stalin cultivated or withheld as it suited him. The series treats the wartime friendship between the democracies and the Soviet Union as a transaction rather than a bond, one whose terms are still visible in the map of postwar Europe.