The Official Voice of Vietnam Veterans of America, Inc. ®
An organization chartered by the U.S. Congress
January/February 2006

New Evidence on the Gulf of Tonkin


Just before midnight on the final day of November 2005, more than 41 years after the event, the National Security Agency declassified a large swath of material related to the August 1964 Gulf of Tonkin Incident. That famous episode in the history of the Vietnam War is now revisited in the release of significant documentation on perhaps the final piece of the puzzle: the communications intercepts that bore on the battle. The new evidence conveys several significant insights.

On August 2, 1964, the U.S. destroyer Maddox fought a battle against several North Vietnamese torpedo boats not long after a coastal raid on the North carried out by American and South Vietnamese special forces. The Johnson administration promptly sent the Maddox, which had withdrawn after the action, back into the Gulf, reinforced by destroyer C. Turner Joy. On the night of August 3, the ships radioed that they were again under attack. The Johnson administration took this repeat attack as a token of aggression and used it to justify the first American bombing of North Vietnam as well as the passage of the Gulf of Tonkin Resolution, which was the legal basis for waging the war in Vietnam.

Events in the Gulf of Tonkin have remained controversial. In the middle of the supposed second attack, the naval commander on the scene sent a dispatch that called into question his own action reports, without any impact on Washington’s decisions. Johnson officials staunchly insisted that its accounts of both incidents were true. The general verdict of history has been that the August 2 battle indeed took place, but that the second incident was a fiction. Even the author of the Navy’s official history of the Vietnam War covering this period, who followed the Johnson script, now concedes the inaccuracy of claims for the night of August 3. The last holdouts among those who sided with the Johnson administration’s version of events relied upon the NSA intercept evidence to buttress their position.

The significance of the new declassifications is that they make the full range of intercept evidence available for the first time. It turns out that the claims originally based on the communications intelligence used only a handful of the NSA intercepts, and they were selectively culled from a much wider array of material. This fact is illuminated in considerable detail in a lengthy paper by NSA historian Robert J. Hanyok, which also is among the newly released documents.

Intercepts used by then-Secretary of Defense Robert S. McNamara to defend the official version of events in 1968 and 1969 investigations have long been contested, and actually do reflect the events of August 2, rather than the alleged second incident. That was the view of NSA deputy director Louis Tordella, CIA senior official Ray Cline, the Senate Foreign Relations Committee, and many historians.

The new material also reveals these startling facts:

  • Only one of four relevant NSA intercept stations took in the message that became central to the debate, while one of the other stations reported a version of the same dispatch that did not sustain the inference that an attack was taking place.
  • Washington officials relied upon the times at which NSA transmitted the intercepted and translated messages to place them within the timeframe of the alleged attack, rather than the times at which North Vietnamese radio operators had originated the messages, which were before any of the alleged events were occurring.
  • The Vietnamese-language original of the key message in which a phrase was subject to interpretation (hurt “sailors” versus damaged “boats”) had disappeared from the files, even though NSA practice typically included plaintext at the end of a message as a technical assistance feature. Two of the five points of the administration argument for the veracity of events relied upon this message. All the others were based on alleged radar, sonar, or visual observations that were increasingly disputed.
  • Confusion over whether a particular radio call sign referred to an individual boat or a unit permitted further distortion to occur.
  • NSA headquarters reports combined elements of different messages without the acknowledgment that was standard procedure to issue a summary containing the starkest possible rendering of available information.
  • The vast majority of NSA intercepts for August 3 conveyed a picture of a quiet North Vietnamese naval communications net, with the bulk of those messages sent pertaining to an effort to recover and tow the two torpedo boats damaged in the August 2 battle, and none of the sighting reports or command traffic that would have been involved in a battle with the Maddox-Turner Joy force.
  • The after-action chronology prepared by an NSA branch chief clearly relied upon the NSA summary reports and the few culled dispatches rather than the large mass of traffic. The agency never updated or modified that chronology and repeatedly issued that document as its sole element of evidence when Tonkin Gulf was investigated by White House boards and congressional panels.

When the Tonkin Gulf incident was investigated by the Senate Foreign Relations Committee and Robert McNamara had to testify, he used only the NSA chronology to prepare for his appearance. Therefore the original distortions in the NSA intercept evidence were perpetuated and observers dug in their heels based on the flimsiest material. See also John Prados’s “Six mysteries of the Tonkin Gulf,” in the August 1989 issue of the Veteran.


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