The united Dtaes, Great Britain and the Soviet Union signed the Limited Test Ban Treaty in 1963.
On August 5, 1963, representatives of the United States, Soviet Union and Great Britain signed the Limited Nuclear Test Ban Treaty, which forbade the testing of nuclear weapons in outer space, underwater or even in the atmosphere.
This treaty was signed by President John F. Kennedy less than three months prior to his assassination, and was considered as a great breakthrough in terms of control of nuclear weapons.