The Limited Test Ban Treaty was signed by the United States, the Soviet Union, and Great Britain in 1963, and it banned all nuclear tests in the atmosphere, in space, or underwater. Because it stopped the spread of radioactive nuclear material through atmospheric testing and set the precedent for a new wave of arms control agreements, the Treaty was hailed as a success. The Treaty was the first of several Cold War agreements on nuclear arms, including the Non-Proliferation Treaty that was signed in 1968 and the SALT I agreements of 1972. In 1974, the Threshold Test Ban Treaty returned to the question of nuclear testing by limiting underground testing of bombs with a yield greater than 150 kilotons.
[https://history.state.gov/milestones/1961-1968/limited-ban| The Limited Test Ban Treaty, 1963 ]