Fat Man was an atomic bomb manufactured in the United States and dropped on the Japanese city of Nagasaki on 9 August, 1945. Six days later, Japan surrendered to the United States, effectively ending the Second World War. The use of atomic weapons in the World War II continues to be a topic of controversy, with some people arguing that the deployment of such weapons was necessary, while others feel that it violated the rules of common decency. Whatever one's feelings about the use of atomic weapons to end the war might be, they certainly reshaped human history.
The nuclear explosion generated by Fat Man was only the third man-made nuclear explosion in history, and the second use of a nuclear weapon in warfare, preceded by the bombing of Hiroshima three days earlier. The bomb released the equivalent of 21 kilotons of TNT, a paltry amount when compared with modern nuclear weapons, but it managed to be quite devastating.
The origins of the name “Fat Man” have been debated. The bomb's creators have suggested that it was named for its distinctive squat shape, which did sort of resemble a fat man sitting on an armchair. Others have said that it was named for British Prime Minister Winston Churchill, one of the more notable large men involved in the Second World War. Whatever the origins of the name were, it was originally intended simply as a code name, so that people could discuss the bomb in secrecy.
The bomb was deployed from a B-29 bomber known as Bockscar from 1,800 feet (550 meters) above the city. Fat Man was an implosion-type device, meaning that the nuclear reaction was generated by a shaped charge which exploded inward, compressing the plutonium core of the bomb to create a nuclear explosion. The design was rather innovative, and some people weren't even certain that Fat Man would work when deployed in action.
These fears proved groundless; within seconds, Fat Man exploded, killing an estimated 45,000 in the city instantly, and causing thousands more to die in the following weeks due to injuries sustained as a result of the blast and the accompanying fires, which ravaged Nagasaki. Within a year, the death toll had risen to 80,000 people. In the decades following, survivors of the bomb, known as Hibakusha or “bomb-affected people,” also experienced a variety of health problems as a result of radiation exposure, ranging from fertility issues to a high incidence of cancer.