Partial Nuclear Test Ban Treaty

Moscow, 5 August 1963

In Moscow on 5 August 1963, U.S. Secretary of State Dean Rusk, British Foreign Secretary Alec Douglas-Home and Soviet Foreign Minister Andrei Gromyko signed the Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water.

Soviet premier Nikita Khrushchev and UN secretary-general U Thant stood behind the foreign ministers during the ceremony, along with diplomats and members of a U.S. Senate delegation.

The instrument was executed in triplicate, with English and Russian texts equally authentic and each original government serving as a depositary.

Three environments, and one further condition

Article I committed the parties to prohibit nuclear-weapon tests and any other nuclear explosions in the atmosphere, in outer space and underwater, including territorial waters and the high seas.

Underground explosions were not categorically exempt: the treaty also prohibited an explosion in any environment if it caused radioactive debris outside the conducting state's territorial limits. It did not prohibit possession, production or deployment of nuclear weapons.

Why it stopped short

Ten days of Moscow negotiations had produced the agreed text on 25 July. The parties abandoned a comprehensive ban because they could not agree on verification and inspection of underground tests.

Signature did not make the prohibitions operative. Other states began signing through the three depositary capitals within days, and the treaty entered into force on 10 October 1963.