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American inability to connect the dots is well known, but what about the intelligence failures of the other side?

In the first two days of the Tet Offensive, North Vietnamese and Viet Cong troops attacked 39 of South Vietnam’s 44 provincial capitals, five of the six largest cities including Saigon, 71 of 242 district capitals, some 50 hamlets, virtually every allied airfield and many other key military targets. The offensive stunned Military Assistance Command, Vietnam (MACV), the White House and the American people. Adding to the impact of the surprise attacks was the fact that they followed in the wake of repeated assurances from both the military and President Lyndon B. Johnson’s administration that progress was being made in the war and that the end was in sight. Despite the fact that the Communists were soundly defeated at the tactical level in the bitter fighting, the Tet Offensive resulted in a great psychological victory for them that proved to be the turning point of the war. It set into motion the events that would lead to Richard Nixon’s election as president, the long and bloody U.S. withdrawal from Southeast Asia and ultimately the fall of South Vietnam.

How did the Tet Offensive achieve such a stunning surprise? United States military intelligence analysts knew that the Communists were planning some kind of spectacular attack, but did not believe it would come during Tet or that it would be nationwide. Still, there were many indicators that the enemy was planning to make a major shift in its strategy to win the war. One of the earliest of these came in March of 1967 when South Vietnamese troops captured a document that made the first mention of a major direct assault on Saigon. Over the ensuing months, there would be a steady stream of additional indicators.

That the Communists might be up to something began to become apparent in April and May, when there was a series of sharp fights between U.S. Marines and North Vietnamese troops in the hills surrounding the remote base at Khe Sanh near the Laotian border in I Corps. At about the same time, additional North Vietnamese forces launched the first of several attempts to capture or destroy the Marine base at Con Thien, just south of the DMZ. In both cases, the engagements differed from the normal pattern of enemy attacks—they were more intense and longer in duration. Why the enemy was increasing the level of combat in those particular areas would not become apparent until much later.

On October 16, 1967, ARVN units in the Mekong Delta found a three-page memorandum from the regional party committee, dated September 2, that used the phrase “winter-spring campaign” and discussed preparations for a new offensive. On October 25, ARVN units operating in the Tay Ninh area captured another document, which discussed a three-pronged offensive designed to defeat the South Vietnamese forces, destroy U.S. political and military institutions and instigate a countrywide insurrection by the masses. According to the captured document, this projected offensive bore the abbreviated designation TCKTKN for Tong Cong Kich–Tong Khoi Nghia (General Offensive–General Uprising). At about the same time, ARVN troops captured yet another document that discussed sapper training and techniques for Viet Cong (VC) and People’s Army of Vietnam (PAVN) personnel to use against South Vietnamese mechanized equipment.

On October 27, the Communists attacked Loc Ninh, a district capital in Binh Long Province, III Corps. Contrary to normal practice, they tried to hold the town, suffering terribly when U.S. forces supported by artillery and air support drove them out. Intelligence officers were puzzled as to why the enemy had stood and fought, risking certain heavy losses for what was essentially a meaningless objective. This battle marked the first time that the Communists had staged coordinated attacks by large units from different divisions. It later became known that the VC objective had been to practice urban assault tactics and large-scale coordinated attacks in preparation for the coming offensive.

On November 4, a U.S. patrol operating in the Central Highlands southwest of the village of Dak To ran into a North Vietnamese main force unit dug into a hillside. As at Loc Ninh, the Communists stayed and fought, sending in elements of the NVA 1st Division and two additional regiments to continue the battle, which lasted for two weeks. In addition to the attack at Loc Ninh and the intense fighting at Dak To, there were other signs that something unusual was afoot. There had been a flurry of attacks in Dinh Tuong province, where the VC traditionally tested new tactics. Additionally, intelligence indicated that Communist desertion rates were down; several reports theorized that this was because the troops had been told that victory was near and that the entire country would soon be liberated.

During the next two months, several other captured documents indicated that a new offensive was in the planning. Perhaps the best known of these documents was a military directive issued by the Central Office South Vietnam B-3 Front Command, which controlled Communist operations in the central part of South Vietnam. It fell into allied hands in mid-November 1967 and called for “many large scale, well-coordinated combat operations” to “destroy or disintegrate a large part of the Puppet [ARVN] army.”

On November 19, the picture became clearer when U.S. troopers from the 2nd Battalion, 327th Infantry, operating in Quang Tin Province in I Corps, captured a 13-page notebook containing a document titled “Ho Chi Minh’s Order for Implementation of General Counteroffensive and General Uprising during 1967 Winter and 1968 Spring and Summer.” This document was translated and disseminated to both U.S. and South Vietnamese intelligence agencies in the form of a detailed memorandum from the Defense Intelligence Agency. The U.S. Embassy in Saigon even put out a press release with a number of details from the notebook and document. Still, the revelation of this intelligence appears not to have had a major impact on allied thinking or preparations.

On November 25, allied forces in Tay Ninh province captured a 10-page document. Dated September 1, 1967, it was essentially a training manual titled “Clearly Understand the New Situation and Mission: Take Advantage of Victories to Surge Forward and Complete[ly] Defeat the U.S. and Puppet Enemy.” It contained a general outline of the strategy and objectives of a new offensive.

In late November, the CIA station in Saigon compiled all the various intelligence indicators and published a report called “The Big Gamble.” This was not really a formal intelligence estimate or even a prediction, but rather “a collection of scraps” concluding that the Communists were preparing to escalate the fighting. This report also put enemy strength at a much higher level than previously supposed. Military intelligence analysts at MACV strongly disagreed with the CIA’s estimate because, at the time, the command was changing the way it was accounting for the enemy and was reducing its estimate of their capabilities.

Nevertheless, as more intelligence poured in, General William Westmoreland and his staff also came to the conclusion that a major enemy effort was probable. All the signs pointed to a new offensive. Most of the increased enemy activity had been along the DMZ the border areas. More intelligence, particularly signals intelligence, showed that there was a significant buildup around Khe Sanh, near the Laotian border in I Corps Tactical Zone. Deciding that this was where the main threat lay, Westmoreland focused much of his attention on the northernmost provinces.

Meanwhile, indications that the enemy was planning something big continued to pile up. On December 4, the 198th Light Infantry Brigade operating in Quang Nam Province captured yet another document that apparently was a directive that delineated the objectives for a coming all-out offensive that would be, according to the document, accompanied by VC cadres operating in the populated areas to instigate an uprising of the people.

Just before Christmas 1967, intelligence reports indicated that there had been a 200 percent increase in truck traffic on the Ho Chi Minh Trail in Laos in October and November. This fact contributed to the conclusion that the enemy was conducting a major buildup.

On January 4, 1968, U.S. troops in the Central Highlands captured another document titled “Operation Order No. 1,” which called for an attack against Pleiku prior to Tet. A few days later, ARVN soldiers captured a similar order for an assault on Ban Me Thuot, although no date was specified.

Concerned with the enemy buildup around Khe Sanh and the new intelligence, Westmoreland requested that the South Vietnamese cancel the coming Tet countrywide cease-fire. On January 8, the chief of the South Vietnamese Joint General Staff (JGS), General Cao Van Vien, told Westmoreland that he would try to limit the truce to 24 hours. South Vietnamese President Nguyen Van Thieu argued that to cancel the 48-hour truce would adversely affect the morale of his troops and the South Vietnamese people. However, he agreed to limit the cease-fire to 36 hours, beginning on the evening of January 29.

On January 21, the North Vietnamese began the first large-scale shelling of the Marine base at Khe Sanh, which was followed by sharp fights between enemy troops and the Marines in the surrounding hills. Westmoreland was sure that this was the opening of the long indicated general offensive. The fact that the Khe Sanh situation looked similar to that which the French had faced in the fateful battle at Dien Bien Phu in 1954 only added increased urgency to the unfolding events there.

Accordingly, Westmoreland ordered the commencement of Operation Niagara II, a massive bombing campaign of suspected enemy positions around Khe Sanh. He also ordered the 1st Cavalry Division (Airmobile) from the Central Highlands to Phu Bai just south of Hue. Additionally, he sent one brigade of the 101st Airborne Division to I Corps to strengthen the defenses of the two northernmost provinces. By the end of January, more than half of all U.S. combat maneuver battalions were located in the I Corps area, ready to meet any new threat.

At the request of II Field Force commander Lt. Gen. Fred C. Weyand, Westmoreland approved strengthening Saigon’s defenses, but not much else was done in a significant way to strengthen other cities and towns. Westmoreland had already determined, at least as far as he was concerned, that the main enemy thrust would come in the north. When the opening attacks of January 30 were followed by even more widespread attacks the next day and night, MACV and the White House were stunned by the offensive’s scope and intensity.

The Tet Offensive represented, in the words of National Security Council staff member William Jorden in a February 1968 cable to presidential adviser Walt Rostow, “the worst intelligence failure of the war.” Nevertheless, after the war, some of those officers who held posts as commanders and intelligence officers in Vietnam at the time of the Tet Offensive asserted that MACV headquarters was fully aware that there had been a change in North Vietnamese strategy, but was surprised only by the actual scale and level of coordination of the Tet attacks.

Many historians and other observers discount such claims and have endeavored to understand how the Communists were able to achieve such a stunning level of surprise. There are a number of possible explanations. First, allied estimates of enemy strengths and intentions were flawed. Part of the problem was that MACV, in an effort to show progress in the war, had purposefully downgraded the intelligence estimates about VC/PAVN strength. CIA analyst Sam Adams later charged that MACV actually falsified intelligence reports to show progress in the war. Whether this accusation was true is subject to debate, but it is a fact that MACV changed the way it counted the enemy, revising enemy strength downward from almost 300,000 to 235,000 in December 1967. U.S. military intelligence analysts apparently believed their own revised estimates and largely disregarded the mounting evidence that the Communists not only retained a significant combat capability but also planned to use that capability in a dramatic fashion.

Former South Vietnamese Colonel Hoang Ngoc Lung, in a postwar monograph about the 1968 offensive written for the U.S. Army, asserts that allied intelligence analysts dismissed many of the captured documents as wishful thinking on the part of the Communists. Some analysts felt that the documents represented merely an expression of the hopes and intentions of the Communists, rather than something they clearly had the capabilities to accomplish—at least as those capabilities were known and assessed by allied commanders and intelligence analysts.

Thus, the allies greatly underestimated the capabilities of their enemy and dismissed new intelligence indicators because they too greatly contradicted prevailing assumptions about the enemy’s strength and capabilities. It was believed that enemy capabilities were insufficient to support a nationwide campaign. These entrenched beliefs about the enemy served as blinders to the facts, coloring the perceptions of senior allied commanders and intelligence officers when they were presented with intelligence that varied with their preconceived notions.

In the same vein, enemy documents and other evidence were discounted because the analysts did not think that the Communists would want to incur the inevitable heavy losses for such questionable objectives. Even if the Communists could occupy any cities, did they have the strength to hold them against the strong reaction of the allied forces? Thus, the reports did not pass the logic test for allied military intelligence analysts. Such an evaluation depends, of course, on who is defining what is logical.

Another problem that had an impact on the intelligence failures in Tet deals with what is known today as “fusion.” The data collected was difficult to assemble into a complete and cohesive picture of what the Communists were doing. The analysts often failed to integrate cumulative information, even though they were charged with producing estimates that should have facilitated combining of different indicators into an overall analysis. Part of this problem can be traced to the lack of coordination between allied intelligence agencies. Most of these organizations operated independently and rarely shared their information with each other. That was true even within the military intelligence structure. This lack of coordination and information sharing impeded both the synthesis of all available intelligence and precluded the fusion necessary to prevent the enemy offensive from being a surprise when it came.

Even if the allied intelligence apparatus had been better at fusion, it would still have had to deal with widely conflicting reports that clouded the issue. True, the intelligence indicated a general offensive in the offing. But a number of other intelligence reports indicated that the enemy was facing extreme hardships in the field and that his morale had declined markedly. It was difficult to determine which reports to believe. Additionally, some indicators that should have caused alarm among intelligence analysts got lost in the noise of developments related to more obvious and more widely expected adversary threats. Faced with evidence of increasing enemy activity near urban areas and along the borders of the country, the allies were forced to decide where, when and how the main blow would fall. They failed in this effort, choosing to focus on the increasing intensity of engagements around Khe Sanh and in other remote areas.

Westmoreland and his analysts failed to foresee a countrywide offensive, thinking that there would be perhaps a “show of force” but that otherwise the enemy’s main effort would be directed at the northern provinces. When indications that PAVN units were massing near Khe Sanh were confirmed by the attack on the Marine base on January 21, this fit well with what Westmoreland and his analysts already expected. Thus, they evaluated the intelligence in light of what they already believed, focusing on Khe Sanh and discounting most of the rest of the indicators that did not “fit” with their preconceived notions about enemy capabilities and intentions.

The result was a colossal level of surprise, the impact of which cannot be overstated. The scope and ferocity of the attacks stunned the American people. And although the offensive resulted in an overwhelming defeat of the Communist forces at the tactical level, the sheer fact that the enemy had pulled off such an offensive and caught the allies by surprise ultimately contributed to victory for the Communists at the strategic level.

While it is clear that there was a massive intelligence failure on the part of the allies, it is appropriate to look at the other side to see what role intelligence played in planning and preparation for the general Communist offensive. This question should be addressed on two levels: What were the Communists trying to achieve with the offensive, and on what assumptions and intelligence assessments did they base their plan?

The decision to launch the general offensive in 1968 was the result of years of internal struggle and heated debates over both policy and military strategy within the Communist camp. While the full nature of these struggles is complex, they were principally over the timing involved in shifting from a protracted war toward a more decisive approach to winning the war; in the end, the more cautious proponents of protracted war were defeated by those who advocated a nationwide general offensive.

Given the severe setbacks that the PAVN and VC had suffered on the battlefield in 1966-67, it is difficult to understand how the decision was reached to escalate the war. The answer lies in khoi nghia, a key concept in Vietnamese Communist ideology. The Vietnamese idea of a general offensive, which in Maoist protracted war theory requires a long struggle, was speeded up by the belief that a general uprising, or khoi nghia, would accompany and support the general offensive in achieving the decisive victory. Through dau tranh, the two-pronged Vietnamese strategy of simultaneous military and political struggle, the Communists believed the revolutionary consciousness of the people would be gradually raised until it would explode in a “great spontaneous combustion.” In the minds of the Communist planners, the general offensive would succeed because the general uprising, seen as the culmination of many years of political dau tranh, would help offset the military advantages of the Americans and sweep the Saigon regime from power. Thus, the general uprising was their ultimate weapon; they believed that in the end, ideological purity and revolutionary zeal would prevail, even in the face of superior American mobility and firepower.

Ideology notwithstanding, a number of Communist documents reveal that members of the Politburo in Hanoi were realistic enough to project three possible outcomes for the general offensive and uprising. In their words, these were:

“First: We would win great victories on the important battlefields…and the American will to commit aggression would be crushed, forcing them to agree to negotiations to end the war in accordance with our goals and conditions.

“Second: Even though we won important victories in many locations, the enemy would have forces left…would launch counterattacks to…continue the fight against us.

“Third: The United States would send in reinforcements, expand the war into North Vietnam, Laos, and Cambodia, and force us to react in order to transform the nature of the war and to break out of their current posture of defeat.”

Having identified those potential outcomes, the Communist leadership then proceeded to let sound military judgment be overcome by revolutionary blinders. As one participant later observed, they “planned for one possibility—that the general offensive–general uprising would certainly secure victory, meaning we did not plan for possible changes or developments in the situation; we never discussed possibilities 2 and 3 laid out in the orders and instructions we received.”

No allowances were made for what today would be called “branch plans.” The same Communist observer admitted, “this mistake grew out of our belief that if we were to launch a general offensive and uprising then we had to gain a decisive victory…our mistake was also the result of a mistaken perception on our part…with an enemy who possessed tremendous resources…any result was possible—either a victory or a temporary defeat. This should have been taken into account when formulating campaign plans and strategic plans.” In practice, however, the Communists planned for the best case, and ignored other possible outcomes.

Given the heavy losses sustained and the failure to achieve tactical success during the offensive, it is clear that the Communists were guilty of some of the same failings that beset MACV in the lead-up to the Tet Offensive. In recent years, a number of Vietnamese unit histories, journal articles and other publications have provided new insight into the other side’s pre-offensive planning. A review of them reveals that the major failures in Communist planning were incorrect assessment of both friendly and enemy capabilities, erroneous reporting and the destructive influence of ideology and “wishful thinking” on sound military judgment.

In all of the sources examined, there is almost universal agreement that the Communist assessment of the situation prior to making the decision to launch the general offensive was seriously flawed. A journal article on the Tet Offensive in the Saigon-Gia Dinh sector, published in 1988 by the Military History Institute of Vietnam, has this to say about that assessment: “The Central Committee’s assessment underestimated the capabilities of the puppet army and puppet government…the response of the American military forces…[and] the capabilities of our political forces.”

The overestimation of the capabilities of their political forces was particularly critical, because it meant that the general uprising that the Communist planners counted on to help offset American military advantages never materialized. Thus, many of the PAVN and VC attacks were doomed from the beginning, by being launched in the face of concentrated American firepower.

It is difficult to fathom how the Communists, badly bloodied by the Americans in the fighting of the previous two years, could underestimate the reaction of the U.S. military. Perhaps they were blinded by their own ideological arrogance.

The Communists’ failure to properly understand the intelligence picture with regard to the strengths and weaknesses of the American and South Vietnamese forces had a catastrophic impact on the scope of the goals set for their troops in the offensive. General Tran Do, in a 1986 address reviewing the successes and failures of the Tet Offensive, asserted that they had “set inappropriate, unreasonable goals for Tet 1968.”

The author of an article in a recent issue of the Vietnamese Military History Journal is even more emphatic in his criticism of the Communist planners, and failure to appreciate battlefield realities and the subsequent consequences. He states: “If at that time we had been more intelligent, if we had evaluated the situation in a more concrete manner, in a more practical manner, or what our comrades commonly call a more truthful manner, the goals we set for ourselves would have been more realistic.”

A Ministry of Defense document agrees, acknowledging that the Communists “set goals that did not match the realities of the actual situation at that time.”

In an assessment of the Tet Offensive in the official PAVN history, the authors state: “We were subjective [italics added] in our assessment of the situation, especially in assessing the strength of the mass political forces in the urban areas. We had somewhat underestimated the capabilities and reactions of the enemy and set our goals too high…we made only one-sided preparations, only looking at the possibilities of victory and failing to prepare for adversity.” Attributing their tactical failures and losses to “subjectivism” is a recurring theme in the Vietnamese assessments of the Tet Offensive.

In the Vietnamese language, Chu Quan, or “subjectivism,” is the opposite of Khach Quan, or “objectivism.” “Subjectivism,” according to Webster’s New World Dictionary, is “any philosophic theory that restricts knowledge…by limiting external reality to what can be known or inferred by subjective standards of truths.” In the case of the Tet Offensive, the Communists had already decided on the outcome of the campaign based on their interpretation of “subjective” truths and were not to be swayed by any realities that flew in the face of those truths.

An official People’s Army history of the war in Eastern Cochin China concludes that “The primary error was our subjective [unrealistic] assessment of the balance of forces, from which we set goals that were too high and threw our entire force into an effort to overrun and capture the cities while neglecting the need to consolidate our hold on the rural countryside.” A similar report documenting the Tet Offensive in the Tri-Thien-Hue theater also acknowledged the role of “subjectivism” in the conduct of planning for the offensive in that region. The report stated: “We failed to fully see the enemy’s dominant position right in our own Tri-Thien theater. This led us to be subjective, to fail to anticipate many measures, and to not stay close to real-world realities so that we could promptly adjust our measures for dealing with the enemy.”

Thus, it is clear that the Communist planners were just as guilty as MACV in failing to heed the indicators that ran contrary to their already predisposed opinions about the possibility of victory. This subjective assessment of enemy capabilities came from a combination of wishful thinking and ideological “groupthink.” Despite the realities of the battlefield, the leaders in Hanoi and the campaign planners had already decided that it would be a great success. One report acknowledged that “in actuality, our plan and our intention at the time allowed for only one eventuality: that is, lowing manner: “We did not have the courage to accurately reflect and present to higher authorities the difficulties we faced and to suggest ideas to overcome those difficulties.”

The result of all this was a hubris that infected both the planners and those who would conduct the actual attacks once the offensive was launched. The offensive was seen almost as a sure thing. A 1988 Vietnamese Military History Journal article discusses this feeling of impending success: “everyone, from the highest-ranking cadre to the lowliest front-line soldier, concentrated on one thing: finishing them off. That was why at the time we burned the huts in our headquarters, because we thought we were leaving and we weren’t coming back…in actual fact everyone concentrated on one outcome and one outcome only…. And we didn’t need to see whether something was contrary to scientific military principles.”

This hubris led to an operational myopia that was just as debilitating to the Communists as it had been to MACV. Having come to the conclusion that conditions were favorable for launching the general offensive-general uprising, the planners and decision-makers were not interested in any intelligence or assessments that may have run contrary to their preconceived notions.

The outcomes of these miscalculations were devastating to the other side. Conservative estimates put Communist losses in 1968 at around 40,000. This number has been disputed, but a review of just a sampling of the historical documentation on the outcome of the offensive demonstrates how badly the Communists had miscalculated when they decided to launch the Tet Offensive.

A report from the Tri-Thien-Hue theater acknowledged that the Communist forces fighting there had suffered heavy losses: “we had 3,600 wounded soldiers alone, not counting guerrillas and village-level cadres; our organizations were in disarray, we were short of food and ammunition, our combat power had declined, and our agents and organizations in the villages and the city had either been driven up into the mountains or had lost contact with our headquarters.”

These losses were staggering in their effect on the National Liberation Front and the Viet Cong. An official history of Military Region 9, which encompassed what the NLF called Western Nam Bo (the Mekong Delta), discusses the situation in late 1968-early 1969 in the following manner: “our main force units were suffering a severe shortage of personnel. Where province units had each possessed two or three battalions before the Tet Offensive, now each province had only one battalion, and each battalion had a strength of only around 100 men. Districts had previously each had a full company, and some districts had 2 or 3 companies, but now each district had only one company made up of a few dozen cadre and soldiers, and some districts had only a platoon left.”

An official history of Military Region 8, Central Nam Bo (operational area just south of Saigon) noted similar difficulties in the aftermath of the offensive in late 1968: “we suffered heavy casualties and were not capable of fighting a protracted battle to finish off the enemy….Our civilian mass movement continued to decline and weaken in each passing day. Our military command cadres at all levels were confused and disorganized in their efforts.”

The horrendous losses incurred by the Communist forces are further reflected in a Vietnamese history of Group 559, the unit tasked with maintaining the Ho Chi Minh Trail. This history notes that “eight times as many wounded were sent back to the rear area [in 1968] as during 1967.” The People’s Army history of the war in Eastern Cochin China perhaps sums up the post-Tet enemy situation best, acknowledging that the shortcomings of the planning and preparation for the offensive “left behind heavy consequences on the battlefield that lasted for the next several years….”

It cannot be denied that there was a major breakdown in American intelligence that contributed to the devastating psychological impact of the Tet Offensive. Nevertheless, it is just as clear that there was a similar major breakdown in the intelligence area on the other side as well—one that cost them 40,000 of their best soldiers. American leaders may have failed to anticipate the offensive because they were blinded by the inability to overcome their already preconceived notions about enemy strength and the need to be positive in order to support a beleaguered presidential administration at home. But the Communists suffered their own form of intelligence blindness. Their failures can be attributed to hubris and ideological fervor. In both cases, the intelligence failures are tantamount to what one of my mentors called, “Drinking your own bathwater.”

Intelligence is what it is; using, abusing or ignoring intelligence indicators for political or ideological purposes is a dangerous exercise that normally has drastic consequences. That was particularly true in the case of the Tet Offensive. In the end, the Communists survived their intelligence failures and went on to achieve ultimate victory. We, on the other hand, did not, and the price was defeat for America and extinction for the Republic of Vietnam.


Originally published in the February 2008 issue of Vietnam Magazine. To subscribe, click here.