The use of atomic bombs on the Japanese cities of Hiroshima and Nagasaki in August of 1945 remains the only instance in which nuclear weapons of any kind have been used in armed conflict. The uranium-based bomb dropped on Hiroshima, Little Boy, killed roughly 70,000 people instantly, while the plutonium-based bomb dropped on Nagasaki three days later, Fat Man, instantly killed roughly 40,000 people.