The first nuclear test ban treaty

The treaty prohibited all nuclear testing in the atmosphere, in outer space and underwater. It still allowed underground testing as long as the radioactive debris generated by the detonation was contained within the territorial limits of the testing state.The treaty was seen as much as a means of safeguarding the environment as it was a way of easing Cold War tensions.

The work towards the treaty intensified after the 1954 US Bikini test which was double the estimated yield and contaminated a Japanese fishing vessel and its crew well outside the exclusion zone.Samples gathered from the fishing vessel allowed scientists such as Joseph Rotblat to calculate the fallout from the blast and figure out how the hydrogen bomb worked.At the time, the public were told that hydrogen bombs were ‘clean’ and didn’t produce much fallout. Rotblat’s calculations suggested that an H-bomb produced a thousand times more fallout than a conventional atomic bomb.The concerns that scientists had over fallout were widely reported in the press and led to strong public pressure against further tests.In May 1955, the UN Disarmament Commission convened its Subcommittee of Five —including the Soviet Union, US, France, UK and Canada—to study and make recommendations to the general assembly, but progress was slow and negiotations frequently deadlocked.Eventually, it took work by groups such as Pugwash Conferences on Science & World Affairs to quietly come up with proposals—using backchannel contacts between the superpowers—to create a workable verifiable treaty that was signed and ratified in 1963.As Tony Long states at wired.com :

By the time the treaty went into force Oct. 10, 1963, 108 nations -- including those with nuclear aspirations of their own -- had affixed their signatures to the document. It would remain the most effective arms control measure on the books until the conclusion of the first SALT treaty between the United States and the Soviet Union in 1972.