"Fat Man" was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare. A Fat Man device was detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second and largest of the only two nuclear weapons ever used in warfare. It was dropped from the Boeing B-29 Superfortress Bockscar piloted by Major Charles Sweeney. Its detonation marked the third nuclear explosion in history. The name Fat Man refers to the wide, round shape. Fat Man was an implosion-type nuclear weapon with a solid plutonium core, and later with improved cores. From Wikipedia