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.
Historical nuclear weapons stockpiles and nuclear tests by country
The United Kingdom became a nuclear power in 1952, and their nuclear arsenal peaked at just under 500 nuclear weapons in 1981. France became a nuclear power in 1960, and French nuclear stockpiles peaked at just over 500 nuclear weapons in 1992. China developed its first nuclear weapon in 1964; its nuclear stockpile increased until the early 1980s, when it stabilized at between 200 and 260. India became a nuclear power in 1974, while Pakistan developed its first nuclear weapon in the 1980s. India and Pakistan currently have around one hundred nuclear weapons each. Pakistan's nuclear stockpile has increased rapidly, and it is speculated that Pakistan might have more nuclear weapons than the United Kingdom within a decade.