The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is an international agreement aimed at preventing the spread of nuclear weapons. It was opened for signature in 1968 and has three main pillars: non-proliferation, disarmament, and the peaceful use of nuclear energy. Countries that join the treaty commit to not developing nuclear weapons and to pursuing disarmament efforts. As of now, the NPT has been signed by 191 countries, making it one of the most widely adhered-to arms control agreements. The treaty recognizes five nuclear-armed states: the United States, Russia, China, France, and the United Kingdom, while encouraging other nations to use nuclear energy for peaceful purposes.