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.
Nuclear-weapon-free zone
The UK, France, and the USA share a nuclear umbrella with the 25 other members of NATO, and the 6 European Union states not part of NATO (Austria, Cyprus, Ireland, Malta, Sweden, Finland) are part of the EU's Common Security and Defence Policy.