What are the Generations of Nuclear Weapons?
Though there are no official definitions of different generations of nuclear weapons, historians and arms control analysts often recognize four general categories, each of which represents a substantial technological advance over the last. Nations developing nuclear weapons tend to develop each stage in turn and rarely skip stages, except occasionally the first. These stages are 1) gun-type fission bombs, 2) implosion-type fission bombs, 3) fusion bombs, and 4) MIRV (multiple independently targetable reentry vehicle) delivered nuclear weapons. Note how there is no unified organizing principle for this scheme; the distinction between the first and second is based on detonation method, the second and third by the type of bomb, and the third and fourth by the delivery system used. First-generation nuclear weapons were initially developed in the United States in 1939-1945 under the auspices of the top secret Manhattan Project. The gun-type construction of the bomb means its operating princ
