The Warning That Left Something to Chance: Intelligence at Tet John Prados Tacoma Park, Maryland Two meanings of the word "chance" are relevant to the present pur- pose. One is chance as a random factor-for this subject the accidental conjunction of chance occurrences that could have furnished warning of a large-scale nationwide North Vietnamese and Vietcong (VC) of- fensive in Vietnam at Tet in 1968. The second relevant meaning is chance as risk. I believe the reasons for the continuing controversy over whether there was a "surprise" at Tet have much to do with these forms of chance. "Surprise" is a loaded word in the intelligence business, and is but slightly less pejorative when applied as historical interpretation. Thus whether the attack at Tet represented a surprise-and intelligence fail- ure-has ever after remained a fervid question, often lurking in the wings of Vietnam discussions, provoking numerous arguments, even forming part of a court case, when the Tet intelligence question be- came enmeshed in the larger dispute over whether falsification oc- curred in compilation of the North Vietnamese Army (NVA) and VC order of battle. The extremes of the Tet intelligence controversy are represented by senior Army officers themselves; there is no need for looking under rugs for perverse so-called revisionist historians purportedly trying to overturn some conventional wisdom. At one extreme is General David R. Palmer, who in a text used at West Point held that Tet had been an intelligence failure comparable to Pearl Harbor.' At the oppo- site end of the spectrum are the officers who held command and intel- ligence posts in Vietnam in January 1968, arguing that Military Assistance Command Vietnam (MACV) knew all about the Tet offen- sive. For the moment we can take as representative of this view a state- ment before a congressional investigating committee on 3 December 1975 by General Daniel O. Graham, who at Tet had been a colonel assigned to MACV intelligence. "We were not surprised by the fact of the Tet Offensive," Graham told the legislators. "We were not sur- The Journal of American-East Asian Relations, Vol. 2, No. 2 (Summer 1993) © 1993 by Imprint Publications, Inc. All rights reserved. 1. Dave Richard Palmer, Summons of the Trumpet: A History of the Vietnam War from a Military Man's Viewpoint (New York, 1984), 228. prised by the massiveness of the numbers of troops committed. What surprised us was the rashness of the Tet attacks."2 One view or the other, as these labels are applied in history, will ultimately lose the battle of interpretation and be called revisionist. Whoever the revisionists turn out to be, however, they will be senior officers of the United States Army who held responsible positions in the military hierarchy. It is time to move forward on interpretation of this history, and a good place to begin is to look at where the idea for an offensive came from and what the United States found out about it. What Did We Know and When Did We Know It? The record and the pattern of military operations across South Viet- nam indicates that Hanoi and the Vietcong began planning for the Tet Offensive sometime in the summer or early fall of 1967. General Will- iam C. Westmoreland, commander of MACV, dates the moment from the time in July that a B-52 bombing mission near the Cambodian bor- der caught a top NVA headquarters and gravely wounded General Nguyen Chi Thanh, senior NVA field commander in the south. Westmoreland's intelligence, or J-2, chief, Brigadier General Phillip B. Davidson, repeats this assessment and relates the strategy to a power struggle he alleges among the top North Vietnamese leadership.3 In truth a great deal remains to be learned about the Vietnamese side of the war, and there is no way to assert with confidence that this was Hanoi's path to a decision. General Thanh's loss certainly was a grievous one, but coincidental in terms of Hanoi's timing of its offen- sive, which depended much more on immutable factors such as the time necessary to assemble the required troops and supplies and move them down the Ho Chi Minh Trail, or infiltrate them by sea into Cam- bodia. The necessary preparation time was considerable. Just to move replacements or troop units to the northernmost portion of South Viet- nam, the Khe Sanh area, required thirty days or more. Sending troops further south took longer. At some point these movements became detectable "observables" in the intelligence jargon. In turn it was pos- sible for the observables to lead to an estimate of Hanoi's intentions. Another avenue making possible some prediction of an offensive was combat intelligence, the day-to-day process of taking and interro- 2. U.S. Congress, House Select Committee on Intelligence, 94th Cong., 1st sess. Hear- ings: U.S. Intelligence Agencies and Activities: The Performance of the Intelligence Community (Washington, D.C., 1975), pt. 5:1653. 3. Phillip B. Davidson, Vietnam At War: The History 1946-1975. (Novato, Calif., 1988), 418-22, 434, 439-50. .