At 8:15 on the morning of August 6, 1945, the Enola Gay, a U.S. B-29 bomber, dropped the first atomic weapon ever used in warfare, a uranium bomb codenamed Little Boy, on the Japanese city of Hiroshima. Descending by parachute, it exploded several hundred feet above the ground in a silent, blinding flash. Within minutes the massive blast and the firestorm it produced had destroyed the majority of the city and killed almost 100,000 people, a third of Hiroshima's population. By the end of 1945, another 35,000 people had died from deadly radiation burns suffered in the attack. Several hours after the destruction of Hiroshima, U.S. President Harry S. Truman, returning from the Potsdam conference aboard the U.S. cruiser Augusta, announced the use of the top secret weapon against Japan. Truman explained that the atomic bomb had been used to save the lives of Americans that would be lost in an invasion of Japan, and would continue to be used until Japan accepted the Allies' terms of surrender. On August 9, Truman spoke publicly about the Hiroshima bombing again, and reasserted his threat to use additional atomic bombs against Japan until it agreed to surrender. Later that day, a second U.S. atomic bomb, this one plutonium-based and codenamed Fat Man, was dropped on the Japanese coastal city of Nagasaki. A third of the city was destroyed, and by the end of the year, some 70,000 of its citizens were dead. On August 15, Emperor Hirohito announced the Japanese surrender on national radio, urging the Japanese people to "endure the unendurable," and the most destructive war in human history had come to an end.