After the successful Trinity nuclear test July 16 , 1945 , which was the very first nuclear detonation , the Manhattan project lead manager J. Robert Oppenheimer recalled : Immediately after the atomic bombings of Japan , the status of atomic weapons in international and military relations was unclear . Presumably , the United States hoped atomic weapons could offset the Soviet Union 's larger conventional ground forces in Eastern Europe , and possibly be used to pressure Soviet leader Joseph Stalin into making concessions . Under Stalin , the Soviet Union pursued its own atomic capabilities through a combination of scientific research and espionage directed against the American program . The Soviets believed that the Americans , with their limited nuclear arsenal , were unlikely to engage in any new world wars , while the Americans were not confident they could prevent a Soviet takeover of Europe , despite their atomic advantage
Trinity nuclear test
Trinity (nuclear test)
Nuclear warfare