With the end of the war drawing near , Truman flew to Berlin for the Potsdam Conference , to meet with Soviet leader Joseph Stalin and British leader Winston Churchill regarding the post-war order . Several major decisions were made at the Potsdam Conference : Germany would be divided into four occupation zones ( among the three powers and France ) , Germany 's border was to be shifted west to the Oder – Neisse line , a Soviet-backed group was recognized as the legitimate government of Poland , and Vietnam was to be partitioned at the 16th parallel . The Soviet Union also agreed to launch an invasion of Japanese-held Manchuria . While at the Potsdam Conference , Truman was informed that the Trinity test of the first atomic bomb on July 16 had been successful . He hinted to Stalin that the U.S. was about to use a new kind of weapon against the Japanese . Though this was the first time the Soviets had been officially given information about the atomic bomb , Stalin was already aware of the bomb project , having learned about it through espionage long before Truman did
Trinity test
Trinity (nuclear test)
Presidency of Harry S. Truman