United States and weapons of mass destruction
The United States is known to have possessed three types of weapons of mass destruction: nuclear weapons, chemical weapons, and biological weapons. The U.S. is the only country to have used nuclear weapons in combat, when it detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki during World War II. It had secretly developed the earliest form of the atomic weapon during the 1940s under the title "Manhattan Project". The United States pioneered the development of both the nuclear fission and hydrogen bombs (the latter involving nuclear fusion). It was the world's first and only nuclear power for four years (1945–1949), until the Soviet Union managed to produce its own nuclear weapon. The United States has the second largest number of deployed nuclear weapons in the world, after Russia.
Nuclear weapons convention
Each year since 1996, the UN General Assembly has passed a resolution calling on all countries immediately to fulfill their disarmament obligation, as articulated by the International Court of Justice, "by commencing multilateral negotiations leading to an early conclusion of a nuclear weapons convention." In 2007, 127 countries voted in favour of the resolution, including four countries with nuclear weapons: China, India, Pakistan and North Korea.