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 6 August 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 9 August 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 more destructive atomic bomb was dropped by the United States on Nagasaki.