NSA Releases History of American SIGINT and the Vietnam War

[updated to clarify paragraph on Tonkin Gulf Incident]

During the Vietnam War, North Vietnamese intelligence units sometimes succeeded in penetrating Allied communications systems, and they could monitor Allied message traffic from within. But sometimes they did more than that.

On several occasions “the communists were able, by communicating on Allied radio nets, to call in Allied artillery or air strikes on American units.”

That is just one passing observation (at p. 392) in an exhaustive history of American signals intelligence (SIGINT) in the Vietnam War that has just been declassified and released by the National Security Agency.

From the first intercepted cable — a 1945 message from Ho Chi Minh to Joseph Stalin — to the final evacuation of SIGINT personnel from Saigon, the 500-page NSA volume, called “Spartans in Darkness,” retells the history of the Vietnam War from the perspective of signals intelligence.

The most sensational part of the history (which was excerpted and disclosed by the NSA two years ago) is the recounting of the 1964 Gulf of Tonkin Incident, in which a second reported North Vietnamese attack on U.S. forces, following another attack two days before, triggered a major escalation of the war. The author demonstrates that not only is it not true, as Secretary of Defense Robert McNamara told Congress, that the evidence of a second attack was “unimpeachable,” but that to the contrary, a review of the classified signals intelligence proves that “no attack happened that night.”

Several other important Vietnam War-era episodes are elucidated by the contribution of SIGINT, including the Tet Offensive, the attempted rescue of U.S. prisoners of war from Son Tay prison, and more.

The author, Robert J. Hanyok, writes in a lively, occasionally florid style that is accessible even to those who are not well-versed in the history of SIGINT or Vietnam.

The 2002 study was released in response to a Mandatory Declassification Review request filed by Michael Ravnitzky. About 95% of the document was declassified. (Unfortunately, several of the pages were poorly reproduced by NSA and are difficult to read. A cleaner, clearer copy will need to be obtained.)

See “Spartans in Darkness: American SIGINT and the Indochina War, 1945-1975″ by Robert J. Hanyok, Center for Cryptologic History, National Security Agency, 2002.

Some background on the Tonkin Gulf Incident from the National Security Archive with links to related documents may be found here.

See also Declassified Study Puts Vietnam Events in New Light by Peter Grier, Christian Science Monitor, January 9, 2008.

No Responses to “NSA Releases History of American SIGINT and the Vietnam War”

  1. Clyde Wilson January 8, 2008 at 8:30 PM #

    I am a retired U.S. Navy cryptologist and I know Del Lang personally. I firmly believe his reports vs. your “story” about NSA fabricating the Gulf of Tonkin.

  2. Allan Giles January 9, 2008 at 11:13 PM #

    Daniel Ellsberg said in his biographical book, “Secrets”, that he was well aware that the Gulf of Tonkin incident was bogus from the day after the initial incident;

    “The messages were vivid. Herrick must have been dictating them from the bridge in between giving orders, as his two ships swerved to avoid torpedoes picked up on the sonar of the Maddox and fired in the darkness at targets shown on the radar of the Turner Joy: “Torpedoes missed. Another fired at us. Four torpedoes in water. And five torpedoes in water…. Have … successfully avoided at least six torpedoes.”

    Nine torpedoes had been fired at his ships, fourteen, twenty-six. More attacking boats had been hit; at least one sunk. This action wasn’t ending after forty minutes or an hour. It was going on, ships dodging and firing in choppy seas, planes overhead firing rockets at locations given them by the Turner Joy’s radar, for an incredible two hours before the stream of continuous combat updates finally ended. Then, suddenly, an hour later, full stop. A message arrived that took back not quite all of it, but enough to put everything earlier in question.

    The courier came in with another single cable, running again, after an hour of relative quiet in which he had walked in intermittently at a normal pace with batches of cables from CINCPAC and the Seventh Fleet and analyses from the State Department and the CIA and other parts of the Pentagon. I was sitting at my desk – I remember the moment – trying to put this patchwork of information in some order for McNaughton on his return, when the courier handed me the following flash cable from Herrick: “Review of action makes many reported contacts and torpedoes fired appear doubtful. Freak weather effects on radar and overeager sonarmen may have accounted for many reports. No actual visual sightings by Maddox. Suggest complete evaluation before any further action taken.”

    It was a little after 2:00 P.M. The message had been sent at 1:27 P.M. Washington time. Half an hour later another message from Herrick, summarizing positive and negative evidence for an attack, concluded: “Entire action leaves many doubts except for apparent attempted ambush at beginning. Suggest thorough reconnaissance in daylight by aircraft.” * …

    …The president’s announcement and McNamara’s press conference late in the evening of August 4 informed the American public that the North Vietnamese, for the second time in two days, had attacked U.S. warships on “routine patrol in international waters”; that this was clearly a “deliberate” pattern of “naked aggression”; that the evidence for the second attack, like the first, was “unequivocal”; that the attack had been “unprovoked”; and that the United States, by responding in order to deter any repetition, intended no wider war.

    By midnight on the fourth, or within a day or two, I knew that each one of these assurances was false.”

    - Daniel Ellsberg, Secrets, pp. 9-12

    I think Ellsberg’s credentials as a truthteller are Golden, and this report seals the deal.

  3. Silbey January 10, 2008 at 1:06 PM #

    Your announcement is a bit confusingly worded. Hanyok’s point is that the _second_ attack did not happen. He does argue that the _first_ attack did happen. Your announcement does not make that distinction clear.

    [You're right. I will modify the text above to clarify. --SA]

  4. Jose PEREA April 4, 2009 at 12:33 PM #

    Please indicate how to order historical crypto material, declassified.

  5. Jim Treanor December 16, 2010 at 6:38 PM #

    What your article omits to mention is the December 2005 (approved for public release in January 2006) memo by NSA’s Director of Policy and Records, Louis F. Giles, in which he states:

    “Nevertheless, while Mr. Hanyok’s analysis of the available COMINT evidence is convincing on its own, the COMINT does not prove that an attack did or did not occur. Unlike the 2 August COMINT where an actual attack message was intercepted, circumstantial evidence and the absence of a 4 August COMINT attack message cannot conclusively prove there was not an attack.”

    Moreover, Robert J. Hanyok’s characterization of North Vietnamese tracking of Maddox and Turner Joy on 4 August as “sporadic”–based apparently on the 3 September 1964 NSA assessment that “the evidence is still inconclusive [about the extent of DRV radar surveillance on 4 August] in light of the virtual absence of trackings on 3-4 August before the second attack”–is at substantial variance with what those of us in USS Turner Joy’s CIC on those dates noted as not infrequent “hump freq” intercepts of North Vietnamese radar emissions, some of them bearing the distinct fingerprints of lockons.

    What that discrepancy suggests at minimum is that–as the Giles memo indicates–whatever message traffic SIGINT acquired during that period is not the conclusive determinant of what did or didn’t occur on the night of 4 August in the Tonkin Gulf. Given that, the Hanyok analysis should not be treated–as it has been in the press and elsewhere–as the last word on the incident.