The plutonium bomb, named “Fat Man” for its shape, was dropped on the city of Nagasaki, Japan, on August 9, 1945. It contained 6.4 kilograms (14 pounds) of plutonium-239. About 20% fissioned, and less than one gram was converted into energy with the equivalent of 21,000 tons of TNT. As many as 80,000 people were killed in the attack.