Little Boy was the U.S. code name of the atomic bomb dropped on Hiroshima.
The uranium-235 bomb was released from the B-29 Enola Gay on August 6, 1945. It detonated over Hiroshima at approximately 8:15 a.m. local time and became the first nuclear weapon used in warfare.
The second atomic bomb, Fat Man, was dropped on Nagasaki three days later. Little Boy and Fat Man used different designs: Little Boy used a gun-type mechanism, while Fat Man used an implosion design based on plutonium.
The bombings occurred during the final crisis of Japan’s war leadership. Japan announced acceptance of Allied surrender terms on August 15, although historians continue to debate the relative importance of the atomic attacks, the Soviet entry into the war, and other pressures on the decision.