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.
2010 NPT Review Conference
The Nuclear Nonproliferation Treaty (NPT), which entered into force in 1970, recognizes five countries as nuclear-weapon states (the United States, Russia, the United Kingdom, France, and China), who commit to pursue disarmament, and the right of other signatories to use nuclear technology for peaceful purposes, conditional upon their non-acquisition of nuclear weapons. Its ratification is nearly universal because it is adhered by 189 states, including five nuclear-weapon states, with the exception of Israel, India, and Pakistan. North Korea left the NPT and tested its first nuclear weapon in 2006.