Codename "Fat-Man", detonated over Nagasaki, it was the 2nd and last nuclear weapon to be used in combat. "Fat Man" was an implosion type weapon using plutonium. A subcritical sphere of plutonium was placed in the center of a hollow sphere of high explosive. Numerous detonators located on the surface of the high explosive were fired simultaneously to produce a powerful inward pressure on the core resulting in a supercritical condition and a nuclear explosion. An estimated 40,000 people were killed outright by the bombing at Nagasaki, and about 25,000 were injured. Thousands would die later from related injuries, poisoning and nuclear fallout.