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.
Treaty on the Prohibition of Nuclear Weapons
According to the International Campaign to Abolish Nuclear Weapons (ICAN), a coalition of non-governmental organizations, leading proponents of a nuclear-weapon-ban treaty include Ireland, Austria, Brazil, Indonesia, Mexico, Nigeria, South Africa and Thailand. All 54 nations of Africa (all but one of which have either signed or ratified the 1996 Treaty of Pelindaba establishing a nuclear-weapon-free-zone in the continent) and all 33 nations of Latin America and the Caribbean (already in a nuclear-weapon-free-zone under the 1967 Treaty of Tlatelolco) had subscribed to common regional positions supporting a ban treaty. The 10 nations of the Association of Southeast Asian Nations (ASEAN), which concluded the Southeast Asian Nuclear-Weapon-Free Zone Treaty, participated in the negotiations, but Singapore abstained from the vote. Many Pacific island nations are also supportive.