A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. As a result, even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives, and a single weapon is capable of destroying an entire city.In the history of warfare, two nuclear weapons have been detonated — both by the United States, during the closing days of World War II. The first event occurred on the morning of 6 August1945, when the United States dropped a uranium gun-type device code-named "Little Boy" on the Japanese city of Hiroshima. The second event occurred three days later when the United States dropped a plutonium implosion-type device code-named "Fat Man" on the city of Nagasaki. These bombings resulted in the immediate deaths of around 120,000 people and even more over time because of injuries sustained and long-term radiation. The use of these weapons was and remains controversial. (See Atomic bombings of Hiroshima and Nagasaki for a full discussion).
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Noun 1. the warhead of a missile designed to deliver an atom bomb (synonym) atomic warhead, thermonuclear warhead, nuke (hypernym) warhead, payload, load (part-holonym) nuclear weapon