National Security Archive Update, September 22, 2009

JOE-1:U.S. Intelligence and the Detection of the First Soviet Nuclear Test, September 1949

For more information contact:
William Burr [National Security Archive] - 202/994-7000

http://www.gwu.edu/~nsarchiv/nukevault/ebb286/

Washington D.C., September 22, 2009 – Sixty years ago tomorrow, on 23 September 1949, President Harry Truman made headlines when he announced that the Soviet Union had secretly tested a nuclear weapon several weeks earlier. Truman did not explain how the United States had detected the test, which had occurred on 29 August 1949 at Semipalatinsk, a site in northeastern Kazakhstan. Using declassified material, much of which has never been published, this briefing book documents how the U.S. Air Force, the Atomic Energy Commission, and U.S. scientific intelligence worked together to detect a nuclear test that intelligence analysts, still unaware of the extent to which the Soviets had penetrated the Manhattan Project, did not expect so soon.

Stalin and the Soviet Politburo were probably stunned by Truman's announcement; they did not know that Washington had a surveillance system for detecting the tell-tale signs of a nuclear test and they wanted secrecy to avoid giving the United States an incentive to accelerate its nuclear weapons activities. (Note 1) Joe-1 (as U.S. intelligence designated it) was also a jolt for U.S. intelligence analysis, which for several years had asserted that the Soviets were unlikely to have the bomb before mid-1953, although mid-1950 was also possible. A few weeks after the test, CIA director Roscoe Hillenkoetter argued that "I don't think we were taken by surprise" because of an error of only a "few months," but not all of his Congressional masters accepted that.