Little Boy was the code name of the atomic bomb dropped on Hiroshima on August 6, 1945.
The United States Army Air Forces used the B-29 bomber Enola Gay to deliver the uranium-235 weapon. The bomb detonated over Hiroshima and caused catastrophic destruction and loss of life. It was the first nuclear weapon used in warfare.
Little Boy used a gun-type nuclear design. Its name is often contrasted with Fat Man, the implosion-type plutonium bomb dropped on Nagasaki three days later. “Thin Man” was an earlier design name that was abandoned, while “Gadget” referred to the first nuclear device tested at Trinity.
The Hiroshima bombing became one factor in the crisis that led to Japan’s surrender, although historians continue to debate how the bombings, the Soviet declaration of war, and internal Japanese politics interacted. Japan announced acceptance of the Allied terms on August 15.