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Surprised at Tet: U.S. Naval Forces in Vietnam, 1968

By Glenn E. Helm

[Originally published in Pull Together, the Newsletter of the Naval Historical Foundation and the Naval Historical Center, vol.36, no.1 (Spring/Summer 1997): 1-5. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the author.]

Awaking to the sound of explosions, Rear Admiral Kenneth L. Veth, Commander U.S. Naval Forces Vietnam (COMNAVFORV), moved to the rooftop of his rented house to witness a dazzling display of rockets and flares lighting the Saigon night sky. All around, the sound of battle during the early hours of 31 January 1968 heralded the arrival of the 1968 Tet Offensive. Armed with automatic weapons and hand grenades, the Admiral and his housemates waited for a ground assault which fortunately never came. During the remaining hours of darkness, Veth kept informed of events by listening to military police and other tactical communications on the radio. Since he spent the night on the roof of his house, he was unable to direct operations from his headquarters.

Despite numerous warnings, the intensity, coordination and timing of the Tet Offensive surprised the allied intelligence community, including naval Intelligence. In addition to a flawed intelligence collection effort, naval Intelligence and COMNAVFORV misunderstood critical information, resulting in American naval forces being improperly deployed and surprised when Saigon and numerous other targets were attacked on 31 January 1968.

During the Tet truce, Task Force (TF) 117 (Riverine Force) was scheduled to deploy into western Dinh Tuong and eastern Kien Phong provinces, where it was expected to interdict intensified enemy resupply efforts. Captain Robert S. Salzer, the commander of the Riverine Force, later called it a "show and tell" operation, remarking, "there was no reason whatsoever to be there. We went up there along the skinniest canal we could, till we ran out of water completely, then we ploughed through the mud some... Nothing much happened. There was no reason for anything to happen. The Vietcong were all the way to the east of us by this time. So much for what [American intelligence] thought they knew." On the morning of 30 January, the task force received word that the Tet truce was canceled. Offensive operations resumed, but infantry units remained near canals for rapid redeployment. The situation in the Delta deteriorated quickly the next morning as enemy forces attacked My Tho, Ben Tre, Cai Lay, Cai Be and Vinh Long. Salzer recalled: "We began to hear rumors that things weren't going quite so well in our splendid isolation. Bill Knowlton, who was a brigadier general then flew in, saying 'My God, it's Pearl Harbor over again.'" A Riverine Army company was airlifted to Vinh Long to support ARVN forces at 1810 on the 31st. Another company was flown to reinforce the defenses of the permanent Riverine base at Dong Tam, near My Tho. During the night, the majority of the task force withdrew to Dong Tam, where they arrived before dawn despite enemy harassment (including an ineffective ambush). In the fiery glow of nearby fighting, the Riverine force was resupplied and moved out at daybreak. At 1550 on 1 February, these forces were hurled into battle in My Tho and, subsequently at Vinh Long and Ben Tre. During the fighting, as normal sources of intelligence temporarily dried up, the Riverine Force became heavily dependant on Air Force-supplied radio-direction-finding fixes for information on enemy unit locations. In the end, the Riverine Task Force was credited with saving the Delta.

In anticipation of increased enemy infiltration of supplies from Cambodia, TF 116 (River Patrol Force or Game Warden), commanded by Captain Paul N. Gray, had deployed nine PBRs (patrol boats, river) to the Cambodian border region. Four PBRs were based at the US Army Special Forces camp at Chau Doc on the upper Bassac River in the northwest of the Mekong Delta. To the immediate east of Chau Doc, five PBRs were deployed to the Special Forces camp at Thuong Thoi in Kien Phong Province to patrol the upper Mekong River. The repositioning of PBRs to Chau Doc may have had little impact on infiltration, but the vessels proved crucial in repelling a major ground attack on the city during Tet. Elsewhere during Tet, TF 116 units engaged enemy forces at My Tho, Ben Tre, Vinh Long, Sa Dec, the Saigon area and the LCU (landing craft, utility) ramp at Hue. Remarking on the enemy's ability to prepare for these attacks without detection, Captain Gray admitted that "...I have no concrete knowledge of how such a logistics miracle was accomplished by the VC in the Delta."

The month of January saw increased patrol activity by Task Force 115 (Coastal Surveillance or Market Time) as the northeastern monsoon abated. There is no evidence that TF 115, commanded by Captain R. Dicori, deployed in a different manner than usual as Tet approached. Even so, a patrol vessel made what might have been one of the first contacts with enemy forces at the start of the offensive, when it intercepted five or six uniformed enemy personnel concealed in an unlighted sampan three miles south of Qui Nhon, late in the evening of 29 January. During Tet, Market Time forces became engaged in a number of firefights involving sampans and provided naval gunfire support to forces ashore. Harbor defense patrols (Operation Stable Door) engaged enemy swimmers during the early hours of 31 January but were unable to prevent damage to the bow of the Norwegian tanker Pelican in Cam Ranh Bay. Despite extensive commitments in support of allied forces ashore during the Tet fighting, TF 115 thwarted four enemy trawlers at the end of February attempting to simultaneously infiltrate supplies into the RVN.

The Navy's operating forces in Vietnam relied on COMNAVFORV's intelligence organization, headed by the Assistant Chief of Staff for Intelligence, Captain Giles C. Upshur, Jr., for all necessary intelligence on potential friends, enemies and operating areas. The organization was also responsible for fulfilling intelligence requirements of higher headquarters and the Defense Intelligence Agency. Each commander subordinate to COMNAVFORV was responsible for maintaining an intelligence collection organization, and all Navy personnel were expected to report information of intelligence value. Naval Intelligence personnel were stationed throughout the RVN, including Coastal Zone and Riverine Area headquarters, Coastal Surveillance Centers, some PBR bases and some Sector Operations and Intelligence Centers. An intelligence officer was assigned to the staff of each of the three Navy task forces. In addition, an intelligence advisor and a counterintelligence advisor were assigned to the Vietnamese Navy. Naval Intelligence Liaison Officers (NILOs), tasked with providing intelligence to COMNAVFORV and allied naval forces within their assigned geographic areas, were stationed in 24 towns and cities, primarily provincial capitals of coastal and Mekong Delta provinces. No boats or watercraft were assigned to NAVFORV with the primary purpose of obtaining intelligence.

The task forces played a significant role in the collection of intelligence. For example, in addition to questioning and detaining Vietnamese nationals, TF 116 inserted Provincial Reconnaissance Units and Navy SEAL (Sea, Air and Land) teams on intelligence collection missions. In support of TF 115, naval aircraft conducted patrols along the Vietnamese coasts. The aircraft detected and photographed merchant shipping, observed patterns of junk movement, and supported surface units during possible submarine contacts. Relevant intelligence reports and analysis went to various intelligence consumers. American and Vietnamese naval intelligence personnel interrogated enemy prisoner and deserters, exploited documents and materials and produced intelligence.

James C. Graham, a CIA employee who served on the Board of National Estimates, recalled, "I think that there was an intelligence failure at Tet, but I think it was composed of many elements... the anatomy of any intelligence failure is always a very complicated thing." Numerous reasons account for the intelligence failure that led to COMNAVFORV and his intelligence organization being surprised by the Tet Offensive. The following list is not exhaustive; it merely provides a basis for understanding the failure. In some cases, there is strong evidence that a particular factor contributed to the failure, in other cases the evidence is less clear but highly suggestive nevertheless.

With a limited staff and a lengthy list of collection requirements, NAVFORV intelligence personnel could expend only a small portion of their efforts seeking evidence of an unprecedented, coordinated, country-wide attack such as the Tet Offensive. In addition, U.S. Navy operational forces generally placed a low emphasis on intelligence collection, and it was only in isolated cases that operational boat skippers were successfully given intelligence briefs and then meaningfully debriefed after an operation. TF 115 and TF 116 failed to collect data on ports, boat identities, routes, cargoes and personnel. Analysis of such information would have assisted the Vietnamese government to control water traffic. Rather than utilizing their special warfare skills for intelligence purposes, operating forces often misused the SEALS as covert infantry units. Their abilities to conduct infiltration and reconnaissance, as well as to run agent nets, were often ignored in the rush to employ them in disrupting and destroying specific enemy targets.

A major problem faced by NAVFORV intelligence was the inability of Allied naval patrol forces to significantly interdict enemy logistic activity along the rivers and coast of the RVN, with the likely exception of large vessels approaching from the open sea. As a result, TF 115, TF 116, and Vietnamese Navy patrols did not obtain evidence of the coming Tet Offensive. Communist forces, particularly those in the Mekong Delta, utilized the waterways of the RVN to position personnel and supplies before the offensive. Yet U.S. Navy coastal and river patrol forces intercepted and captured virtually none of this water traffic during the several months prior to Tet. Despite a significant increase in boat and personnel detention in January 1968, NAVFORV captured a mere 22 weapons, 6.5 tons of rice and no ammunition.

The basic difficulty confronting allied naval forces attempting to interdict the covert movement of enemy supplies and forces on or across waterways was that patrol forces were overstretched and sometimes poorly utilized. A study of the Mekong Delta completed in the summer of 1967 tallied 732 miles of major waterways, exclusive of the Rung Sat mangrove swamp. Approximately 90 PBRs were available to cover this area, of which a maximum of 30 two-boat units were continuously on patrol. They could not keep all likely areas of enemy activity under constant surveillance. In practice, PBRs patrolled only those areas of VC activity identified in regular intelligence reports. An important source of these reports was aerial surveillance by NILOs who did not have operational control of aircraft, since they were merely passengers on Army and Air Force planes. Although NAVFORV had a requirement for daily surveillance, aircraft were typically available only three days per week and were not equipped for operations at night, the time of most enemy activity.

A March 1967 study determined that PBR tactics (assuming a 10-hour night) included four hours of drifting with the engine shut down, two hours underway at less than 12 knots, and 4 hours underway at over 12 knots. PBRs could detect sampans at 500-1000 yards with radar and other equipment, but only at 100-500 yards without it. However, on a quiet night, one could hear PBRs operating at high speed more than three miles away. SEAL teams conducting ambushes along rivers frequently reported hearing and seeing enemy signals, presumably warning of approaching PBRs, as much as 30 minutes before their arrival.

COMNAVFORV knew that communist forces used the waterways in the Third Riverine Area (the south and southwestern portions of III Corps), including the Nha Be/Saigon, Dong Nai, Vam Co Tai and Vam Co Dong rivers, for transportation and supply. Allied security in this area, including the control of river crossing points, varied enormously. In some places, it was virtually non-existent. For example, the Bo Bo Canal in Long An Province was particularly well situated for the transport of supplies from communist base areas in Cambodia. An intelligence advisor remarked that unless allied forces gained control of these waterways, "they will continue to be used at will by the VC/NVA...they will remain basic routes for infiltration, supply and crossing points for the VC/NVA." The Senior Intelligence Advisor in the Third Riverine Area during Tet claimed that Vietnamese naval forces were too slow and that, "The VC use our rivers at will. To effectively stop them the Third Riverine needs [US Navy] PBRs, SEALS, and Seawolves [helicopters]. Without the above the VC will continue to run supplies, and troops whenever they desire."

The Fourth Coastal Zone, located along the Cambodian border in the far west of the Mekong Delta, was an area through which significant amounts of enemy supplies moved from Cambodia into the RVN. Working together, the NILO at Ha Tien, American advisors, and the Vietnamese Sub-Sector Chief had developed an agent network capable of providing early warning of large scale overland movement of supplies, but they could not obtain rapid aerial photographic reconnaissance to confirm reports of infiltration. Moreover, communication with the outside remained uncertain due to an inadequately performing generator. The nearest aircraft were located along the coast at Rach Gia, about 50 miles from the border and even farther from the RVN island of Phu Quoc, located half-way between mainland RVN and the Cambodian port of Sihanoukville, through which a great deal of communist supplies were arriving. Aircraft were only available in the vicinity of Phu Quoc when not needed on the mainland, and ready reaction to surveillance needs was considered marginal.

Coastal surveillance resulted in relatively few interceptions of enemy personnel and material. Although this was ascribed at the time to the effectiveness of patrols which discouraged the enemy, it was more likely due to patrolling inefficiencies. Vietnamese Navy assets similarly were subject to poor utilization, often being used for base defense rather than aggressive patrolling. Referring to Coastal Group 12, a Vietnamese Navy unit in I Corps with responsibility for patrolling lagoons, an American advisor remarked, "Unfortunately, they perform routine patrols unsatisfactorily in that the junks are prone to anchor and the crew go to sleep, day or night." A fellow advisor commented "The attitude [of] `let the Americans do it' prevailed." In all fairness, some units conducted creditable patrols, but others were judged barely satisfactory and some were considered totally unacceptable.

The quality of Vietnamese naval units often fluctuated over time, due in large measure to the attitude of their commanding officers. One advisor remarked that emphasis on numbers of boardings, inspections and detected contacts reduced the effectiveness of patrols. For example, one naval unit spent several hours almost daily inspecting a fishing fleet located 3-4 miles off the coast, in the same place on a regular basis. Enemy units presumably noticed the pattern and slipped along the coast while the patrol unit was otherwise occupied. American crews were also affected by pressure to produce results. An advisor who served in the Mekong Delta observed, "I mean [American PBR crews will] stop anybody and take in 50 people and call them suspects if they feel that the pressure is on them to come up with some suspects."

Another factor was the lack of Vietnamese language capability among NAVFORV intelligence personnel. Few Americans managed to master the Vietnamese language before Tet. In fact, language training for Navy intelligence personnel remained inadequate until 1970, when the Navy finally devoted greater resources to the problem. A lack of fluency in Vietnamese meant that Naval Intelligence personnel were at the mercy of sometimes insincere or even traitorous Vietnamese personnel. The Intelligence Advisor to the Vietnamese Navy summed up the need for Vietnamese language training:

"In my opinion it is not sufficient to rely upon the fact that many Vietnamese officers speak English. Not only are other nationals quite pleased and flattered to find Americans who speak their language, there are important operational requirements as would prevent to a greater extent conversations by Vietnamese "around" the advisor. It is important for Intelligence oriented officers to be fully aware of what is going on around them and to be able to read newspapers and other printed material to be fully effective. The lack of these capabilities detracts from the advisory and intelligence effort."

One Coastal Surveillance Zone advisor remarked "I don't know if language training would have been of help, however it might have given me some insight into those I was to advise."

The failure of Navy personnel to understand the Vietnamese language was a component of the systemic problem of the American effort in Indochina, and one linked to the one-year tour of duty. In the field, less than six CIA officers at a time together with a small number of military advisors and intelligence personnel assigned to American units were proficient in the Vietnamese language.

Poor communication skills and short tours of duty combined with unfortunate results. One advisor to the Vietnamese Fleet Patrol felt unable to impress upon his Vietnamese counterpart the potential that his ship had for collecting intelligence. Although American liaison personnel could only gather a small percentage of available information, he considered the Vietnamese Navy's ability to "read the people" a potentially prime source of intelligence. He noted that the Vietnamese Navy could become "more of an intelligence collection agency and less of an intelligence collation agency if it could only tap the potential intelligence available through personal contact with millions of people annually."

Prior to Tet, allied intelligence failed to recognize changing enemy strategy. Analysts believed the communists would be foolish to attack urban areas where they would be exposed to superior allied firepower. The communists would thereby give up their perceived control over their casualty rate while waiting for the United States support the Republic of Vietnam to weaken.

Other issues commonly associated with the Tet intelligence debacle such as enemy deception, enemy indecision, false alerts, analysts' fear of crying wolf, poor information sharing, and information processing difficulties also contributed to the failure to provide warning of the upcoming offensive.

Of particular importance to the issue of whether the Navy had sufficient warning of Tet was all- source intelligence available to Admiral Veth and his intelligence organization on 27 January. This information painted a dramatic picture of enemy activity and indicated that a major enemy offensive was imminent. It should have produced a maximum state of American vigilance as Tet approached. Widespread communist attacks in the northern portion of the Republic of Vietnam during the night of 29/30 January could have provided 24 hours warning, yet NAVFORV was still unprepared.

COMNAVFORV and his intelligence organization were surprised by the intensity, coordination and timing of the Tet Offensive, as evidenced by Admiral Veth's presence at his residence during the first wave of attacks on Saigon. Of the many factors that led to the intelligence community's surprise at the offensive, the misguided belief that enemy forces would not run the risk of attacking the cities and towns of the RVN is paramount. The belief that an attack during the most important Vietnamese holiday was an almost unthinkable enemy option was similarly misguided. Had the allied intelligence community placed greater emphasis on intelligence collection, and acted properly on the intelligence that they did receive, the Tet Offensive may never have found its way into the history books as one of the greatest intelligence lapses in the post-World War II era.

For further reading on intelligence and the Tet Offensive:

Ford, Ronnie E. Tet 1968: Understanding the Surprise. London: Frank Cass, 1995.

Helm, Glenn E. The Tet 1968 Offensive: A Failure of Allied Intelligence. MA thesis. Tempe AZ: Arizona State University, 1989.

Hoang Ngoc Lung. The General Offensives of 1968-69. Washington: US Army Center of Military History, 1976.

Oberdorfer, Don. Tet. Garden City NY: Doubleday, 1971.

Wirtz, James J. The Tet Offensive: Intelligence Failure in War. Ithaca NY: Cornell University Press, 1991.


Published: Thu Nov 02 16:56:18 EDT 2017