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JAMES R. ARNOLD
The basic armoured vehicle of the war was the M-113 armoured personnel carrier (APC). Combat experience quickly showed the need to increase the armour and firepower of the APC. 'Technicians bolted extra armour along the sides to protect against RPGs, belly armour to shield against mines and an armoured cupola for the commander's.50cal machine-gun. The addition of two side-mounted M-60 machine-guns converted the vehicle to the Armored Cavalry Assault Vehicle. Mechanized units used the ACAVs as light tanks. They had surprising cross-country ability. The combination of mobility and firepower demonstrated to the high command that armour could usefully contribute to the war. Westmoreland wrote: 'The ability of mechanized cavalry to operate effectively in the Vietnamese countryside convinced me that I was mistaken in a belief that modern armor had only a limited role in the fighting in Vietnam.'
Yet the attached analysis provided by the mission, apparently reflecting the prevailing belief in Westmoreland's headquarters, was that these orders were 'ambiguous' as to the time fixed for the attack and possibly represented 'internal propaganda' designed to inspire the enemy's troops.
By the beginning of 1968, the Allies had assembled a considerable armoured force. The US Army's contingent included the famous 11th Armored Cavalry Regiment, seven divisional cavalry squadrons, seven mechanized battalions, two tank battalions and an independent tank company, and five cavalry troops supporting light infantry and airborne units. The Marine Corps also had considerable armoured assets. The crack 1st Australian Task Force provided an APC troop. Ten South Vietnamese armoured cavalry squadrons were available.
When the South Vietnamese General Staff later studied the Tet Offensive they hit upon the essential basis for the intelligence failure. Having been taught American doctrine, they were primarily concerned with the Communist 'capabilities and not his intentions'. Capabilities could be quantified, and it was clear to all the Allies that the enemy could not hope to capture and hold urban objectives. Therefore, intelligence officers dismissed all indications that the enemy intended to try anyway.
An aerial view of Khe Sanh. Communist pressure against this base caused Westmoreland to divert increasing strength to the northern I Corps region. With hindsight, it appears he was duped by a skilful Communist diversionary build-up.
A second major factor beyond the inability of military intelligence to assess accurately the signs of enemy build-up accounts for the Tet Offensive's surprise. When the American high command examined their strategic maps at the beginning of 1968, they focused on the northernmost provinces bordering the so-called demilitarized zone (DMZ) that separated North and South Vietnam. Since mid-1967, Westmoreland had been shuffling strength northward in response to the enemy's growing strength. By the New Year he had positioned a tremendous amount of available military resources there. The positions included a series of fortified, but isolated, Marine Corps posts along the DMZ. The high command, and President Johnson in particular, feared that a major assault across the border and from neighbouring Laos might turn one of these bases into a Dien Bien Phu. Mid-January patrol actions seemed to confirm the high command's worries: two dug-in NVA divisions had surrounded the Marine Corps combat base of Khe Sanh. In sum, by January 1968, enemy pressure had over-stretched American resources. Distracted by the threat in the north, the US high command seriously underestimated the enemy's potential for major, nationwide attacks.
General Fred Weyand sensed too many troops were deployed along the Cambodian border. He urged Westmoreland to recall them to positions closer to Saigon. This redeployment proved to be Westmoreland's best decision before Tet.
Major General Charles Stone (back row, third from right) carefully prepared defensive plans in ease the Communists struck. His care paid great dividends in the defence of Pleiku.
Major General Frederick C. Weyand commanded the American field forces in III Corps Tactical Zone. His command stretched from Saigon out to the Cambodian border. According to Westmoreland's recent strategy, 39 of his 53 manoeuvre battalions were operating against enemy bases along the Cambodian border. Unbeknown to Weyand, as the Americans shifted out from the urban area, the Communists marched in. However, radio intercepts and the lack of contact with the enemy in the border area alarmed Weyand. On 9 January he telephoned Westmoreland to explain his concern and to recommend that forces return from the border. In a key decision, Westmoreland agreed. When the Communists struck, the number of American battalions within the urban zone had doubled. Their presence made a tremendous difference.
Elsewhere, as January progressed, disquieting signs of enemy build-up continued and they too prompted countermeasures. Early in the month, the 4th Division in the Central Highlands captured a plan for an attack on Pleiku. In mid-January, 101st Airborne captured plans for an attack on the province capital of Phu Cuong.
However, the Communist practice of compartmentalizing planning paid dividends. Since neither of the plans mentioned anything except the immediate activities of the units involved, American intelligence officers failed to foresee that they were part of a nation-wide plan. Consequently, counter- measures were left to local commanders. On 26 January the 4th Division commander, Major General Charles Stone, assembled all area commanders and prepared a coordinated response should an attack take place. His foresight stands in sharp contrast to that of other commanders. He also moved a tank company to Pleiku as a mobile reserve. Similarly, a few days later, Westmoreland ordered the 4th Cavalry Squadron to relocate near Saigon's Tan Son Nhut airbase. He reckoned that 'they would provide a ready mobile reserve with impressive firepower'. Both of these small shifts helped when the attack came.
By January, Westmoreland had become sufficiently alarmed to request that the South Vietnamese cancel the coming Tet cease-fire. On 8 January the chief of the South Vietnamese Joint General Staff, General Cao Van Vien, told Westmoreland that he would try to limit the truce to 24 hours. A week later, President Thieu argued that to cancel the 48-hour cease-fire would adversely affect his nation and its soldiers. He agreed to limit the ceasefire to 36 hours, beginning on the evening of 29 January. The South Vietnamese government promised to announce the change one day before it was to take effect. In the event it failed to make the announcement in a timely, useful way. In the IV Corps region south of Saigon, for example, the order cancelling the Tet ceasefire reached headquarters shortly after 10 p.m., a mere four and a half hours before the attacks began.