| Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water | |||
|---|---|---|---|
 Participation in the Partial Test Ban Treaty
| |||
| Type | Arms control | ||
| Signed | 5 August 1963 | ||
| Location | Moscow, Soviet Union | ||
| Effective | 10 October 1963 | ||
| Condition | Ratification by the Soviet Union, United Kingdom, and United States | ||
| Parties | 126, plus 10 signed but not ratified (see complete list) | ||
| Depositaries | Governments of the United States of America, United Kingdom of Great Britain and Northern Ireland, and Union of Soviet Socialist Republics | ||
| Languages | English and Russian | ||
| Full text | |||
 Partial Test Ban Treaty at Wikisource | |||
The Partial Test Ban Treaty (PTBT), formally known as the 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, prohibited all test detonations of nuclear weapons except for those conducted underground. It is also abbreviated as the Limited Test Ban Treaty (LTBT) and Nuclear Test Ban Treaty (NTBT), though the latter may also refer to the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which succeeded the PTBT for ratifying parties.
Negotiations initially focused on a comprehensive ban, but that was abandoned because of technical questions surrounding the detection of underground tests and Soviet concerns over the intrusiveness of proposed verification methods. The impetus for the test ban was provided by rising public anxiety over the magnitude of nuclear tests, particularly tests of new thermonuclear weapons (hydrogen bombs), and the resulting nuclear fallout. A test ban was also seen as a means of slowing nuclear proliferation and the nuclear arms race. Though the PTBT did not halt proliferation or the arms race, its enactment did coincide with a substantial decline in the concentration of radioactive particles in the atmosphere.
The PTBT was signed by the governments of the Soviet Union, the United Kingdom, and the United States in Moscow on 5 August 1963 before it was opened for signature by other countries. The treaty formally went into effect on 10 October 1963. Since then, 123 other states have become party to the treaty. Ten states have signed but not ratified the treaty.