Little Boy was the U.S. atomic bomb dropped on Hiroshima three days before Nagasaki was bombed.
The bomb was released over Hiroshima on August 6, 1945, by the B-29 bomber Enola Gay. Little Boy used a uranium-235 gun-type design and was the first nuclear weapon used in warfare. The explosion destroyed much of the city and caused enormous loss of life, with many additional deaths occurring later from injuries and radiation effects.
On August 9, the United States dropped Fat Man, a plutonium implosion-type weapon, on Nagasaki. These attacks were part of the final crisis surrounding Japan’s surrender, though historians continue to debate how the bombings, the Soviet declaration of war, and Japan’s internal political struggle each influenced the final decision.
Little Boy should not be confused with Trinity, the first nuclear device detonated in a test, or Fat Man, the weapon used at Nagasaki. The two wartime weapons had different designs and fuel materials.