This lengthy report was State Department Bureau of Intelligence and Research's contribution to the first National Intelligence Estimate on the nuclear proliferation, NIE 100-6-57. Written at a time when the United States, the Soviet Union, and the United Kingdom were the only nuclear weapons states, the “Fourth Country” problem referred to the probability that some unspecified country, whether France or China, was likely to be the next nuclear weapons state. Enclosed with letter from Helmut Sonnenfeldt, Division of Research for USSR and Western Europe, to Roger Mateson, 4 June 1957, Secret

This US analysis of the likelihood of nuclear proliferation during the next decade was finished only days after the first Chinese nuclear test on 16 October. The report analyses the implications of this test, as well as programs in India, Israel, Sweden, West Germany, Italy, Japan, Canada, and others. The National Intelligence Estimate (NIE) argued that India was the only new state likely to develop nuclear weapons, concluding that “there will not be a widespread proliferation …over the next decade.”

This NIE comes to the general conclusions that “there will not be a widespread proliferation of nuclear weapons over the next 10 years” and discusses programs in various countries (Israel, China, Sweden, India, West Germany, Japan, etc.) This copy includes newly declassified references to the Israeli nuclear weapons program, including the conclusion that “the Israelis, unless deterred by outside pressure, will attempt to produce a nuclear weapon some time in the next several years.”