On 5 August 1963, the Limited Test Ban Treaty is signed, prohibiting any nuclear weapon tests in the atmosphere, in outer space and under water. Underground explosions are not prohibited as long as they do not cause radioactive waste outside the territorial limits of the state responsible for the test. Secretary of State Dean Rusk signs for the United States, Foreign Minister Andrei Gromyko for the Soviet Union and Alec Douglas-Home for the United Kingdom. The treaty comes into force on 10 October 1963. The photo shows United Nations Secretary General U Thant (centre), and to his right, Nikita Khrushchev, First Secretary of the Communist Party of the Soviet Union.