Both the United States and the Soviet Union drifted apart after the Russian Revolution of 1917, the Russian Civil War and the Paris Peace Conference. Diplomatic and extensive trading relationships were established under Roosevelt, but relations soured following the Soviet invasion and absorbion of the Baltic States and Poland. After Hitler broke the MolotovRibbentrop Pact the Western powers worked closely with the Soviet Union during the Second World War. Distrust re-emerged as Stalin's plans for placing Eastern Europe in the Soviet Union's sphere of influence became apparent towards the war's end, and came to the fore at the Potsdam Conference, just before the atomic bombing of Hiroshima and Nagasaki. Interviewees include George F. Kennan, Zola Zarubina, Hugh Lunghi and George Elsey. The pre-credits scene shows the US Congress nuclear bunker at The Greenbrier, and introduces the television series by explaining how for several decades the world was close to a nuclear holocaust.