American Cryptology during the Cold War, 1945-1989: Book II: Centralization Wins, 1960-1972 [Part 2, excised] [open pdf - 7MB]
This is the second section of book two in Thomas Johnson's history of the National Security Agency (NSA) during the Cold War. It contains pages 495-652, which encompasses three chapters on Vietnam, entitled: NSA in Vietnam: Building the Effort - The Early Years; From Tonkin to Tet - The Heart of the War; and the Withdrawal. This section also contains a glossary of abbreviations used throughout the book, a list of sources, and an index.
National Security Archive: http://www.gwu.edu/~nsarchiv/