At the Potsdam Conference starting in late July 1945 , the Allies met to decide how to administer the defeated Nazi Germany , which had agreed to unconditional surrender nine weeks earlier on May 7 and May 8 , 1945 , VE day . Serious differences emerged over the future development of Germany and Eastern Europe . At Potsdam , the US was represented by a new president , Harry S. Truman , who on April 12 succeeded to the office upon Roosevelt 's death . Truman was unaware of Roosevelt 's plans for post-war engagement with the Soviet Union , and more generally uninformed about foreign policy and military matters . The new president , therefore , was initially reliant on a set of advisers ( including Ambassador to the Soviet Union Averell Harriman and Secretary of the Navy James Forrestal ) . This group tended to take a harder line towards Moscow than Roosevelt had done . Administration officials favoring cooperation with the Soviet Union and the incorporation of socialist economies into a world trade system were marginalized . The UK was represented by a new prime minister , Clement Attlee , who had replaced Churchill after the Labour Party 's defeat of the Conservatives in the 1945 general election
Potsdam Conference
Potsdam Conference
Origins of the Cold War