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 . The attack was made by three Soviet army groups . On that same day , a second equally destructive atomic bomb was dropped by the United States on Nagasaki
Yalta Conference
Yalta Conference
Second Sino-Japanese War