Democratic Peace Theory - democratic states go to war to keep non-democratic states to arm.
he Treaty on the Non-Proliferation of Nuclear Weapons, also Nuclear Non-Proliferation Treaty (NPT or NNPT) is a treaty to limit the spread (proliferation) of nuclear weapons, opened for signature on July 1, 1968. There are currently 189 countries party to the treaty, five of which have nuclear weapons: the United States, Russia, the United Kingdom, China and France (also permanent members of the UN Security Council).
Only four recognized sovereign states are not parties to the treaty: India, Israel, Pakistan and North Korea. India, Pakistan and North Korea have openly tested and declared that they possess nuclear weapons. Israel has had a policy of opacity regarding its own nuclear weapons program. North Korea acceded to the treaty, violated it, and withdrew from it in 2003.