Little Boy was the codename for the atomic bomb dropped on Hiroshima on 6 August 1945.
The uranium-235 bomb was carried by the B-29 bomber Enola Gay and detonated over Hiroshima at about 8:15 a.m. local time. It was the first nuclear weapon used in warfare. The explosion destroyed much of the city and killed or injured large numbers of civilians.
Little Boy used a gun-type fission design, in which one subcritical piece of uranium was fired into another to create a supercritical mass. Its design differed from the implosion weapon used at Nagasaki.
The Hiroshima bombing became one of the major events that shaped Japan’s surrender, although historians continue to debate the relative importance of the atomic attacks, the Soviet declaration of war, and the internal Japanese political crisis. Little Boy is commonly confused with Fat Man, the bomb used against Nagasaki three days later.