In the wake of Allied victory , Truman journeyed to Europe for the Potsdam Conference . He was there when he learned the Trinity test — the first atomic bomb — on July 16 had been successful . He hinted to Joseph Stalin that the United States 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 atomic espionage — long before Truman did
Trinity test
Trinity (nuclear test)
Harry S. Truman