Little Boy was the United States codename for the atomic bomb dropped on Hiroshima before Japan surrendered.
The uranium gun-type weapon was dropped from the B-29 Enola Gay on August 6, 1945. It exploded over Hiroshima and caused catastrophic destruction and loss of life. Little Boy was the first nuclear weapon used in warfare.
Three days later, the United States dropped Fat Man, a plutonium implosion weapon, on Nagasaki. The two bombs had different designs and codenames, so they are often mistakenly treated as identical weapons. Japan’s surrender decision followed these attacks, the Soviet Union’s entry into the war against Japan, and intense internal debate among Japanese leaders.
Hirohito’s surrender broadcast referred to a “new and most cruel bomb” without naming Hiroshima or Little Boy. The formal surrender occurred on September 2, nearly a month after the Hiroshima attack. The bombings remain among the most consequential and controversial events of the twentieth century.