This section provides an overview of the history of the Manhattan Project, the key organizations involved, the science behind the bomb, and more.
The story of U.S.-U.K. nuclear partnership is one of both collaboration and division.
France became the fourth country to possess nuclear weapons after its first test in 1960. While development was slowed by the impact of World War II, the achievements of early French research were critical for nuclear development worldwide.
India tested its first atomic bomb in 1974 but did not develop a significant nuclear arsenal until more than two decades later.
Israel is widely believed to possess nuclear weapons, but has never confirmed the existence of its nuclear program.
Amid a bitter rivalry with India, Pakistan became a nuclear power after testing its first bombs in 1998.