A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions
- fission
- or a combination of fission and fusion reactions
Both bomb types release large quantities of energy from relatively small amounts of matter producing a nuclear explosion.
The first nuclear test explosion on July 16, 1945
Then it was used against Japan in August 1945. Two bombs were exploded in Hiroshima & Nagasaki, resulting in thousands of deaths, not only on the day of the bombings, but for the years that followed also.
August 29 marks the International Day against Nuclear Tests
Nuclear Risk from The Bulletin.org which also calculates the Doomsday Clock.