Details: This poster shows a color image of a mushroom cloud created from a hydrogen bomb explosion.
A nuclear weapon is a weapon which derives its destructive force from nuclear reactions of fission or fusion. In the history of warfare, nuclear weapons have been used only twice, both during the closing days of World War II on the Japanese cities of Hiroshima and Nagasaki. Since these bombings, nuclear weapons have been detonated on over two thousand occasions for testing and demonstration purposes. The Teller–Ulam design is the nuclear weapon design concept used in most of the world's nuclear weapons. Colloquially referred to as 'the secret of the hydrogen bomb,' because it employs hydrogen fusion to generate neutrons, in most applications the bulk of its destructive energy comes from uranium fission, not hydrogen fusion.