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.
Views on the nuclear program of Iran
Iranian politicians compare its treatment as a signatory to the NPT with three nuclear-armed nations that have not signed the NPT: Israel, India, and Pakistan. India and Pakistan developed an indigenous nuclear weapons capability, and it is widely suspected that Israel has as well: Israel by 1966, India by 1974, and Pakistan by 1990.