Fat Man was the code name of the atomic bomb dropped on Nagasaki during Japan’s 1945 surrender crisis.
The United States detonated Fat Man over Nagasaki on August 9, 1945, three days after Little Boy was used against Hiroshima. Fat Man was an implosion-type nuclear weapon that used plutonium, whereas Little Boy used a different gun-type design and uranium.
The bomb was carried by Bockscar, a Boeing B-29 Superfortress commanded by Major Charles W. Sweeney. Nagasaki was the secondary target after clouds and smoke obscured Kokura, the primary target. The weapon exploded at approximately 11:02 a.m. local time.
Fat Man was the second and last nuclear weapon used in warfare. Its destruction, combined with the Soviet entry into the war against Japan and the continuing military crisis, formed part of the chain of events leading to Japan’s acceptance of the Allied surrender terms. The bomb’s rounded shape inspired its name.