Spartans in Darkness: American SIGINT and the Indochina War, 1945-1975
http://www.fas.org/irp/nsa/spartans/index.html
Mostly declassified text of a 2002 history of American signals intelligence during the Vietnam War. Among other noteworthy incidents, claims that no attack by North Vietnamese boats occurred in the Gulf of Tonkin in 1964, the incident which caused the expansion of U.S. troops in Vietnam. From the National Security Council, posted by the Federation of American Scientists.
