Little Boy was the codename of the first atomic bomb used against Japan in World War II.
The United States dropped Little Boy on Hiroshima on August 6, 1945. It was a uranium-235 gun-type weapon carried by the B-29 bomber Enola Gay, piloted by Colonel Paul Tibbets.
The explosion destroyed much of Hiroshima and caused enormous loss of life, both immediately and from radiation and injuries afterward. The bombing was followed three days later by the use of a different plutonium implosion weapon, Fat Man, against Nagasaki.
Little Boy was not the first atomic device detonated by the United States; that was Trinity, an experimental test in New Mexico on July 16, 1945. The Hiroshima weapon was the first atomic bomb used in warfare. Japan’s surrender followed the bombings, the Soviet declaration of war, and intense internal debate within the Japanese government.