Atmospheric nuclear explosions are associated with mushroom clouds, although mushroom clouds can occur as a result of large chemical explosions. It is also possible to have an air-burst nuclear explosion without these clouds. Nuclear explosions produce radiation and radioactive debris.
The nuclear weapon was first detonated in combat on 6 August 1945, when the United States dropped a uranium gun-type device on the Japanese city of Hiroshima. The second and last use of a nuclear weapon in combat occurred three days later when United States dropped a plutonium implosion-type device on the Japanese city of Nagasaki. These bombings resulted in the immediate deaths of around 120,000 people while more died over time due the nuclear radiation.