What was the U.S. underground nuclear testing (UGT) program?
In 1992, UGT was an important element in the nuclear weapons evaluation program. Nuclear testing, which involved the detonation of actual weapons, provided unique data that enhanced military capability and improved U.S. nuclear weapons safety. Prior to 1959, U.S. nuclear tests were conducted above ground, in the atmosphere and under water. After 1959, all U.S. nuclear tests were conducted underground. The United States has also conducted a number of joint tests with the United Kingdom. In 1963, the United States and the Soviet Union signed the Limited Test Ban Treaty (LTBT) prohibiting nuclear weapons testing in the atmosphere, in outer space and under water. In 1974, the two Superpowers signed the Threshold Test Ban Treaty (TTBT), which restricted underground nuclear tests to a maximum of 150 kilotons (kt). See International Treaties and Agreements, for a more detailed discussion of these Treaties. The United States performed a total of 1,054 nuclear tests (including joint U.S./U.K. t
