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 of the United States
This table is not comprehensive, as numerous facilities throughout the United States have contributed to its nuclear weapons program. It includes the major sites related to the U.S. weapons program (past and present), their basic site functions, and their current status of activity. Not listed are the many bases and facilities at which nuclear weapons have been deployed. In addition to deploying weapons on its own soil, during the Cold War, the United States also stationed nuclear weapons in 27 foreign countries and territories, including Okinawa (which was US-controlled until 1971,) Japan (during the occupation immediately following World War II), Greenland, Germany, Taiwan, and French Morocco then independent Morocco.