Weapon of mass destruction
The only country to have used a nuclear weapon in war is the United States, which dropped two atomic bombs on the Japanese cities of Hiroshima and Nagasaki during World War II. There are eight countries that have declared they possess nuclear weapons and are known to have tested a nuclear weapon, only five of which are members of the NPT. The eight are China, France, India, North Korea, Pakistan, Russia, the United Kingdom, and the United States.
List of states with nuclear weapons
The Soviet Union tested its first nuclear weapon ("RDS-1") in 1949. This crash project was developed partially with information obtained via espionage during and after World War II. The Soviet Union was the second nation to have developed and tested a nuclear weapon. The direct motivation for Soviet weapons development was to achieve a balance of power during the Cold War. It tested its first megaton-range hydrogen bomb ("RDS-37") in 1955. The Soviet Union also tested the most powerful explosive ever detonated by humans, ("Tsar Bomba"), with a theoretical yield of 100 megatons, intentionally reduced to 50 when detonated. After its dissolution in 1991, the Soviet weapons entered officially into the possession of the Russian Federation. The Soviet nuclear arsenal contained some 45,000 warheads at its peak (in 1986); the Soviet Union built about 55,000 nuclear warheads since 1949.