Since the end of World War II, US military power has been instrumental in maintaining peace and prosperity for the United States and its allies. During the Cold War both superpowers relied primarily on thousands of nuclear weapons to keep the strategic balance between the West and the Soviet Union. These weapons were kept on strategic alert under the Mutual Assured Destruction doctrine which ensured adequate second strike capability by both sides, thus making any nuclear exchange unwinnable. In addition to the five original Nuclear Weapons States (US, USSR, China, UK and France), two other states (India and Israel) developed nuclear weapons capabilities during the Cold War period. Both India and Israel are democracies and countries friendly to the United States.Since the collapse of the Soviet Union, an unstable state (Pakistan) and a hostile state (North Korea) successfully tested nuclear weapons. Furthermore, another hostile state (Iran) is violating the Nuclear Non-Proliferation Treaty (NPT) and is believed to pursue nuclear weapons capability. As more states acquire nuclear weapons the danger of a deliberate or accidental nuclear detonation increases. Nuclear power programs use the same technologies - uranium enrichment and plutonium reprocessing capabilities - that can be used to make weapons.