 The United States and the Soviet Union put an end to the war by attacking the Japanese with a new weapon (on the United States' part) and an incursion into Manchuria (on the Soviet Union's part).On August 6, 1945, an American B-29 bomber, the "Enola Gay", dropped the first atomic bomb used in combat on Hiroshima, killing tens of thousands and leveling the city.On August 9, 1945, the Soviet Union renounced its non-aggression pact with Japan and attacked the Japanese in Manchuria, fulfilling its Yalta Conference pledge to attack the Japanese within three months after the end of the war in Europe.