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 Free World Policy
1. We, the Ministers for Foreign Affairs of Brazil, Egypt, Ireland, Mexico, New Zealand, Slovenia, South Africa and Sweden have considered the continued threat to humanity represented by the perspective of the indefinite possession of nuclear weapons by the nuclear-weapon states as well as by those three nuclear-weapons-capable states that have not acceded to the Nuclear Non-Proliferation Treaty, and the attendant possibility of use or threat of use of nuclear weapons. The seriousness of this predicament has been further underscored by the recent nuclear tests conducted by India and Pakistan.