Battle of Khe Sanh

Khe Sanh is an area in in northwestern Quang Tri Province, in what was northern part of what was South Vietnam. A United States Army Special Forces base was first established in 1964, manned by Civilian Irregular Defense Group light forces. In 1966, a small United States Marine Corps base was built next to it. The main Battle of Khe Sanh, however, was a multidivision confrontation, from January to April 1968, between Communist and allied forces.

The main 1968 battle was also called Operation Scotland, Operation Pegasus, was conducted , Republic of Vietnam (South Vietnam), between 21 January and 8 April 1968 during the Vietnam War. The combatants were elements of the United States of America (U.S.) III Marine Amphibious Force (III MAF), elements of the South Vietnamese Army of the Republic of Vietnam (ARVN) and two to three division-size elements of the People's Army of Viet Nam (PAVN). Massive United States Air Force support, using what, for the time, were new techniques for controlling "danger-close" fires, was called Operation Niagara.

In March 1968, an overland relief expedition (Operation Pegasus) was launched by a combined Marine/Army/South Vietnamese task force that eventually broke through to the Marines at Khe Sanh. The battle itself was a tactical victory for the Marines, but the strategic implications of the battle still remain unclear.

Preliminaries

The camp

The village of Khe Sanh was the seat of government of Huong Hoa district, an area of Bru Montagnard villages and coffee plantations, situated about seven miles from the Laotian frontier on [[National Highway 9 (Vietnam}|Route 9]], the northernmost transverse road in South Vietnam. The badly deteriorated Route 9 ran from the coastal region, through the western highlands, and then crossed the border into Laos. The origin of the combat base lay in the construction by U.S. Army Special Forces of an airfield in August 1962 outside the village at an old French fort. The camp then became a Special Forces outpost of the Civilian Irregular Defense Groups (CIDG), whose purpose was to keep watch on PAVN infiltration along the border and to protect the local population. In November 1964 the Green Berets moved their camp to the Xom Cham Plateau, the future site of KSCB.

Infiltration routes

During the winter of 1964, Khe Sanh became the location of a launch site for the highly-classified MACV-SOG, first established near the village and was later moved to the French fort. From there, reconnaissance teams were launched into Laos to explore and gather intelligence on the PAVN logistical system known as the Ho Chi Minh Trail, operated by the 559th Transportation Group.

Things remained quiet in the Khe Sanh area through 1966. Even so, General Westmoreland insisted that it not only be occupied by the Marines, but that it be reinforced. He was vociferously opposed by General Lewis W. Walt, the Marine commander of I Corps. Walt argued heatedly that the real target of the American effort should be the pacification and protection of the population, not chasing PAVN and the NLF in the hinterlands. Westmoreland won out, however, and the 1st Battalion, 3rd Marine Regiment (1/3 Marines) was dispatched to occupy the camp and airstrip on 29 September. By late January 1967, 1/3 was relieved by Bravo Company, 1st Battalion, 9th Marines. A single company was replacing an entire battalion. One of the mysteries surrounding the Battle of Khe Sanh was why, after running roughshod over the Marines over the defense of the base at Khe Sanh, Westmoreland allowed the drawdown.

The plateau camp was permanently manned by the U.S. Marines during 1967, when they established an outpost next to the airstrip. This base was to serve as the western anchor of Marine Corps forces, which had tactical responsibility for the five northernmost provinces of South Vietnam known as I Corps. The Marines' defensive system stretched below the Demilitarized Zone (DMZ) from the coast, along Route 9, to Khe Sanh. During 1966 the regular Special Forces troops had moved off the plateau and built a smaller camp down Route 9 at Lang Vei, about half the distance to the Laotian border.

Border battles

During the second half of 1967, the North Vietnamese instigated a series of actions in the border regions of South Vietnam. All of these attacks were conducted by regimental-size PAVN/National Front for the Liberation of South Vietnam (NLF, or Viet Cong) units, but unlike the usual hit-and-run tactics used by communist forces, these were sustained and bloody affairs.

Battle of Con Thien

In early October, PAVN intensified battalion-size ground probes and sustained artillery fire against Con Thien, a hilltop stronghold in the center of the Marine's defensive line south of the DMZ in northern Quang Tri Province. Mortar rounds, artillery shells, and 122mm rockets fell randomly, but incessantly upon the base. The September bombardments ranged from 100 to 150 rounds per day, with a maximum on 25 September of 1,190. The American commander in Vietnam, General William Westmoreland responded by launching Operation Neutralize, an aerial and naval bombardment campaign designed to break the siege. For seven weeks, American aircraft delivered from 35,000 to 40,000 tons of bombs in nearly 4,000 airstrikes.

Battle of Song Be

On 27 October, a PAVN regiment attacked an Army of the Republic of Vietnam (ARVN) battalion at Song Be, capital of Phuoc Long Province. The North Vietnamese fought for several days, took casualties, and fell back. Two days later, the 273rd NLF Regiment attacked a Special Forces camp near the border town of Loc Ninh, in Binh Long Province. Troops of the U.S. 1st Infantry Division were able to respond quickly. After a ten-day battle, the attackers were pushed back into Cambodia. At least 852 North Vietnamese soldiers were killed during the action, as opposed to 50 American and South Vietnamese dead.

Battle of Dak To

Combat on Hill 875, the most intense of the battles around Dak To.

The heaviest action took place near Dak To, in the central highlands province of Kontum. There, the presence of the 1st PAVN Division prompted a 22-day battle that saw some of the most intense close-quarters fighting of the entire conflict. Somewhere between 1,200 and 1,600 North Vietnamese troops were killed while 362 members of the U.S. 4th Infantry Division, the 173rd Airborne Brigade, and ARVN Airborne elements were killed in action. Ominously, three of the four battalions of the 4th Infantry and the entire 173rd were rendered combat ineffective during the battle.

American intelligence analysts were quite baffled by this series of enemy actions. There appeared to be no logic behind the sustained PAVN/NLF offensives, other than to inflict casualties on the allied forces. This they accomplished, but the casualties absorbed by the North Vietnamese seemed to negate any direct gains they might have obtained. The border battles did, however, have two significant consequences that were unappreciated at the time — they fixed the attention of the American command on the border regions and they drew American and ARVN forces away from the coastal lowlands and cities.

Hill fights

On 24 April 1967, a patrol from Bravo Company became engaged with a PAVN force of unknown size north of Hill 861. This action prematurely triggered a North Vietnamese offensive aimed at taking Khe Sanh. The PAVN forces were in the process of gaining elevated terrain before the launching of the main attack. The 2/3 and 3/3 Marine battalions reinforced KSCB (Khe Sanh Combat Base) and were given the task of pushing the North Vietnamese off of Hills 861, 881 North, and 881 South. North Vietnamese forces were driven out of the area around Khe Sanh after suffering 940 casualties. The Marines suffered 155 killed in action and 425 wounded. In order to prevent PAVN observation of the main base at the airfield (and their possible use as firebases), the hills of the surrounding Khe Sanh Valley had to be continuously occupied and defended by separate Marine elements, thereby spreading out the defense.

In the wake of the hill fights there was a lull in PAVN activity around Khe Sanh. By the end of May, Marine forces were again drawn down from two battalions to one, the 1st Battalion 26th Marines. Lieutenant General Robert Cushman Jr. relieved General Walt as commander of III MAF in June. On 14 August, Colonel David E. Lownds took over as commander of the 26th Marine Regiment. There were sporadic actions in the vicinity during the late summer and early fall, the most serious of which was the ambush of a supply convoy on Route 9. This proved to be the last overland attempt at resupply for Khe Sanh until the following March. During December and early January there were numerous sightings of PAVN troops and activities in the Khe Sanh area, but the sector remained relatively quiet.

The American command in Saigon initially believed that combat operations around Khe Sanh during the summer of 1967 were just part of a series of minor North Vietnamese offensives in the border regions. That appraisal was altered when it was discovered that PAVN was moving major forces into the area during the fall and winter. A build-up of Marine forces took place and actions around Khe Sanh commenced when the Marine base was isolated. During a series of desperate actions that lasted 77 days, Khe Sanh Combat Base (KSCB) and the hilltop outposts around it were under constant North Vietnamese ground, artillery, mortar, and rocket attacks.

Decisions

A decision then had to be made by the American high command: either commit more of the limited manpower in I Corps to the defense of Khe Sanh or abandon the base. General Westmoreland regarded this choice as quite simple. In his memoirs he listed the reasons for a continued effort:

"Khe Sanh could serve as a patrol base for blocking enemy infiltration from Laos along Route 9; as a base for SOG operations to harass the enemy in Laos; as an airstrip for reconnaissance planes surveying the Ho Chi Minh Trail; as the western anchor for defenses south of the DMZ; and as an eventual jump-off point for ground operations to cut the Ho Chi Minh Trail."

Leading Marine officers, however, were not all of the same opinion. General Cushman, the new III MAF commander, supported Westmoreland (perhaps wanting to mend Army/Marine relations after the departure of Walt). Arguments offered by other Marine officers against remaining included: that the real danger to I Corps was from a direct threat to Quang Tri City and other urban areas; that a defense would be pointless as a threat to infiltration, since PAVN troops could easily bypass Khe Sanh; that the base was too isolated and that the Marines "had neither the helicopter resources, the troops, nor the logistical bases for such operations … The weather was another critical factor because of the poor visibility and low overcasts attendant to the monsoon season made such operations hazardous to say the least." Brigadier General Lowell English (assistant commander 3rd Marine Division) complained that the defense of the isolated outpost was ludicrous. "When you're at Khe Sanh, you're not really anywhere. You could lose it and you really haven't lost a damn thing."

As far as Westmoreland was concerned, however, all he needed to know was that PAVN had massed large numbers of troops for a set-piece battle. Making the prospect even more enticing was that the Combat Base was in an unpopulated area where American firepower could be fully brought to bear without having to worry about civilian casualties. The opportunity to engage and destroy a formerly elusive enemy that was moving toward a fixed position promised a victory of unprecedented proportions.

At all costs

Battle is joined

Marine intelligence confirmed that, within a period of just over a week, the 325th PAVN Division had moved into the vicinity of the base and two more divisions were within supporting distance. The 324th Division was located in the DMZ area 10-15 miles north of Khe Sanh while the 320th Division was within easy reinforcing distance to the northeast. They were supported logistically from the nearby Ho Chi Minh Trail. As a result of this intelligence, KSCB was reinforced on 13 December by the 1/9 Marines.According to the official PAVN history, by December 1967 the North Vietnamese had in place, or within supporting distance

• the 304th, 320th, 324th, and 325th Infantry Divisions
• independent 270th infantry Regiment
• five artillery regiments (the 16th, 45th, 84th, 204th, and 675th)
• three AAA regiments (the 208th, 214th, and 228th)
• four tank companies
• one engineer regiment
• one independent engineer battalion
• one signal battalion
• numerous local force units.

At positions west of Hill 881 South and north of Co Roc Ridge, across the border in Laos, the North Vietnamese established artillery, rocket, and mortar positions from which to launch attacks by fire on the base and to support its ground operations. PAVN 152mm artillery pieces had a range of around ten and one-half miles. The 130mm gun, introduced later in the battle, had a range of nineteen miles. The heaviest Marine ordnance at Khe Sanh, the 155mm, had a range of only nine miles. This discrepancy in ranges was used by the North Vietnamese in order to avoid counterfire. They were assisted in their emplacement efforts by the continuing bad weather of the winter monsoon.

During the rainy night of 2 January 1968, six men dressed in black uniforms were seen outside the defensive wire of the main base by members of a listening post. After failing to respond to a challenge, they were fired upon and five were killed outright while the sixth, although wounded, escaped. This event prompted General Cushman to reinforce Colonel Lownds with the rest of the 2nd Battalion, 26th Marines. This marked the first time that all three battalions of the 26th Marine Regiment had operated together in combat since the invasion of Iwo Jima during the Second World War. In order to cover a defilade near the Rao Quan River, Foxtrot, Golf, Hotel and H&S Companies of 2/26 was immediately sent out to occupy Hill 558, with Echo Company 2/26 maning hill 861A.

On 20 January, La Thanh Tone, a PAVN lieutenant of the 14th Anti-Aircraft Company, 325th Division, defected at the base and laid out the plans for an entire series of North Vietnamese attacks. Hills 881 South, 861, and the main base itself would be simultaneously attacked that same evening. At 00:30 on 21 January, Hill 861 was attacked by approximately 300 North Vietnamese troops. The Marines, however, were prepared. The North Vietnamese infantry, though bracketed by artillery fire, still managed to penetrate the perimeter of the defenses and were only driven back after severe close-quarters combat.

The main base was then subjected to an intense mortar and rocket barrage. Hundreds of mortar rounds and 122mm rockets slammed into the base, leveling most of the above-ground structures. One of the first enemy shells set off an explosion in the main ammunition dump. Many of the artillery and mortar rounds stored in the dump were thrown into the air and detonated on impact within the base. Soon after another shell hit a cache of CS tear gas, which saturated the entire area. Hours after the bombardment ceased, the base was still in danger. At around 10:00, the fire ignited a large quantity of C-4 and other explosives, rocking the base with another series of detonations. PAVN forces, however, did not use the opportunity to launch a ground attack.

Simultaneous with the bombardment at KSCB was an attack launched against the Huong Hoa District headquarters. There, elements of the 66th Regiment, 304th PAVN Division were opposed by Bru CIDGs, South Vietnamese Regional Force (RF) troops led by their Army advisors, and the first platoon of Marines from Oscar Company, part of the Combined Action Program or CAP. Oscar Company was commanded by LT Thomas Stamper, and O-1 was led by SGT John Balanco. (Another CAP Oscar platoon, O-2, commanded by SGT Roy Harper, stationed at the west end of Khe Sanh village on the North side of Route 9, was hit simultaneously. They fought off the enemy, and later joined the O-1 Marines at the District HQ. Oscar-3, near the Combat Base, were on alert, but were not attacked.) The forces managed to hold out until the morning of the 22nd, when helicopters were sent in for their extraction. The Marine CAP men and the Army advisors were stunned to learn that "no RFs or Bru with their weapons would be allowed on the helos to return to the Combat Base." An Army captain, Bruce B. G. Clarke, the senior U.S. Army District advisor for Huong Hoa, and his team medic, SFC Jim Perry, refused evacuation under such restraints and marched their men to the SOG compound, FOB 3 (located next to the Combat Base) by way of a hidden trail. The Special Forces of FOB 3 also used Bru (Montagnard) troops in their CIDG (Civilian Irregular Defense Group) program, and were happy to have the Bru. They also accepted the Marines of CAP Oscar who helped man their lines and run patrols and activities throughout the Siege.

This attack revealed that the 304th PAVN Division had just arrived from North Vietnam with all three of its regiments, the 9th, 24th, 66th, the 68B Artillery Regiment, and the 14th Anti-Aircraft Battalion. Attached in support was the 24th Artillery Battalion. The division took up positions southwest of the Combat Base. There has been a significant discrepancy, however, as to what infantry units of the 325th Division remained in the Khe Sanh sector. An ARVN document study conducted after the battle concluded that only one regiment, 95C, remained at Khe Sanh. According to the study, two regiments of other divisions held blocking positions on Route 9 east of the base. They were the 31st Regiment of the 341st Division and possibly a regiment of the 324th Division. Two battalions of the 3rd Regiment later moved south to Hue to participate in the battle for that city during the latter stages of the Tet Offensive.

To eliminate any threat to their flank, the North Vietnamese made the decision to attack Laotian Battalion BV-33, located at Ban Houei Sane, on Route 9 in Laos. The battalion was assaulted on the night of 23 January by three PAVN battalions supported by seven tanks. The Laotians were overrun, and many fled to the Special Forces camp at Lang Vei. This action in Laos, not the attack three weeks later at Lang Vei, marked the first time that the North Vietnamese had committed an armoured unit to battle.

Due to the arrival of the 304th Division, KSCB was further reinforced by the 1st Battalion, 9th Marine Regiment on 22 January. Five days later, the final reinforcements arrived in the form of the 37th ARVN Ranger Battalion, which was deployed more for political than tactical reasons. PAVN artillery made its debut on the battlefield on 24 January, when an artillery bombardment began with Hill 881 South, moved on to Hill 861, and then worked over the main base. The Marines and ARVN dug in and hoped that the approaching Tet truce (scheduled from 29-31 January) would provide some respite. On the afternoon of the 29th, however, the 3rd Marine Division notified Khe Sanh that the truce had been cancelled. The Tet Offensive was about to begin.

Operation Niagara

During January, the recently installed electronic sensors of Operation Muscle Shoals (later renamed Igloo White), which were undergoing test and evaluation in southeastern Laos, were alerted by a flurry of PAVN activity along the Ho Chi Minh Trail opposite the northwestern corner of South Vietnam. It was due to the nature of these activities, and the threat that they posed to KSCB, that General Westmoreland ordered Operation Niagara I, an intense intelligence collection effort on PAVN activities in the vicinity of the Khe Sanh Valley.

Niagara I was completed during the third week of January, and the next phase of the operation, Niagara II was launched on the 21st, the day of the first PAVN artillery barrage. The Marine Direct Air Support Center (DASC), located at the Combat Base, was responsible for the coordination of air strikes with artillery fire. An airborne battlefield command and control center (ABCCC), in the form of a C-130 aircraft, directed incoming strike aircraft to forward air control (FAC) spotter planes, which, in turn directed them to targets either located by themselves or radioed in by ground units. When weather conditions precluded FAC-directed strikes, bombers, especially B-52 heavy bombers using ARC LIGHT tactics, were directed to their targets by either a Marine AN/TPQ-10 radar installation at KSCB or by Air Force Combat Skyspot AN/MSQ-77 stations.

Thus began what many considered "the most concentrated application of aerial firepower in the history of warfare", up to that time. On an average day 350 tactical fighter-bombers, 60 B-52s, and 30 light observation or reconnaissance aircraft operated in the skies near the base. Westmoreland had already ordered the nascent Igloo White to assist in the Marine defense. On 22 January, the first sensor drops took place and, by the end of the month, 316 acoustic and seismic sensors had been dropped in 44 strings. The Marines at KSCB credited 40 percent of intelligence available to their fire support coordination center to the sensors.

By the end of the battle of Khe Sanh, U.S. Air Force assets had flown 9,691 tactical sorties and dropped 14,223 tons of bombs on targets within the Khe Sanh area. Marine Corps aviators had flown 7,098 missions and released 17,015 tons. Naval aircrews, many of whom were redirected from Operation Rolling Thunder strikes against North Vietnam, flew 5,337 sorties and dropped 7,941 tons of ordnance in the area.

Not even this amount of unleashed firepower was enough to calm the anxiety of American leaders in Washington. On 1 February General Earle G. Wheeler, chairman of the Joint Chiefs of Staff, raised the issue with Westmoreland of "whether tactical nuclear weapons should be used if the situation at Khe Sanh should become that desperate." Westmoreland replied that their use would probably not be required. He added, however, that if the situation did change dramatically, "I visualize that either tactical nuclear weapons or chemical agents would be active candidates for employment." Westmoreland then established a small study group to examine the consequences of what was nicknamed Fracture Jaw. Westmoreland later wrote that "Washington so feared that some word of it might reach the press that I was told to desist.

While battles were raging around the Combat Base, other engagements were taking place in the headquarters at Hue/Phu Bai, Saigon, and the Pentagon. An intense interservice struggle over who should control aviation assets supporting not just Khe Sanh, but the entire American effort in Southeast Asia was being waged. Westmoreland had given his deputy commander for air operations, Air Force General William W. Momyer, the responsibility for coordinating all air assets during the operation to support KSCB. This caused problems for the Marine command, which possessed its own aviation squadrons that operated under their own close air support doctrine. The Marines were extremely reluctant to relinquish authority over their aircraft to an Air Force General.

The command and control arrangement then in place in Southeast Asia went against the grain of Air Force doctrine, which was predicated on the single air manager concept. One headquarters would allocate and coordinate all air assets, distributing them wherever they were considered most necessary, and then transferring them as the situation required. The Marines, whose aircraft and doctrine were integral to their operations, were under no such centralized control. On 19 January Westmoreland passed his request for Air Force control up the chain of command to CINCPAC in Honolulu and there it stayed.

Meanwhile, heated debate arose among Westmoreland, Commandant of the Marine Corps GEN Leonard Chapman Jr. and Chief of Staff of the Army GEN Harold Johnson. Johnson backed the Marine position due to his concern over protecting the Army's air assets from Air Force co-option. Westmoreland went so far as to threaten to resign if his wishes were not obeyed. As a result, on 7 March, for the first time during the Vietnam War, air operations were placed under the control of a single manager. General Westmoreland had won this battle.

Fall of Lang Vei

The Tet Offensive was launched prematurely in some areas on 30 January. On the following night, a massive wave of PAVN/NLF attacks swept throughout South Vietnam, everywhere that is, except Khe Sanh. The launching of the largest enemy offensive thus far in the conflict did not shift Westmoreland's focus away from Khe Sanh. A press release prepared on the following day (but never issued), at the height of Tet, showed that he was not about to be distracted. "The enemy is attempting to confuse the issue …I suspect he is also trying to draw everyone's attention away form the greatest area of threat, the northern part of I Corps. Let me caution everyone not to be confused."

There had not been much activity (with the exception of patrolling) thus far during the battle for the Green Berets of Detachment A-101 and their four companies of Bru CIDGs stationed at Lang Vei. That changed radically during the early morning hours of 7 February. The Americans had previous forewarning of PAVN armour in the area from Laotian refugees from camp BV-33. Although PAVN was known to possess two armoured regiments, it had not yet fielded an armoured unit in South Vietnam, and besides, the Americans considered it impossible for them to get one down to Khe Sanh without it being spotted by aerial reconnaissance.

It still came as a shock to the Special Forces troopers at Lang Vei when 12 tanks attacked their camp. The Soviet-built PT-76 amphibious tanks of the 202nd PAVN Armored Regiment churned over the defenses, backed up by an infantry assault by the 7th Battalion, 66th Regiment and the 4th Battalion of the 24th Regiment, both elements of the 304th Division. The ground troops had been specially equipped for the attack with satchel charges, tear gas, and flame throwers. Although the camp's main defenses were overrun in only 13 minutes, the fighting lasted several hours, during which the Special Forces men and Bru CIDGs managed to knock out at least five of the tanks.

The Marines at Khe Sanh had a plan in place for providing a ground relief force in just such a contingency, but Colonel Lowndes, fearing a PAVN ambush, refused to implement it. Lowndes also rejected a proposal to launch a helicopter extraction of the survivors. During a meeting at Da Nang at 07:00 the next morning, Generals Westmoreland and Cushman accepted Lowndes' decision. Army Lieutenant Colonel Jonathan Ladd ,commander, 5th Special Forces Group), who had just flown in from Khe Sanh, was reportedly, "astounded that the Marines, who prided themselves on leaving no man behind, were willing to write off all of the Green Berets and simply ignore the fall of Lang Vei."

Ladd and the commander of the SOG compound (whose men and camp had been incorporated into the defenses of KSCB) proposed that, if the Marines would provide the helicopters, the SOG recon men would go in themselves to pick up any survivors. The Marines continued to oppose the operation until Westmoreland actually had to issue an order to Cushman to allow the rescue operation to proceed. It was not until 15:00 hours that the relief effort was launched and it was successful. Of the 500 CIDG troops at Lang Vei, 200 had been killed or were missing and 75 more were wounded. Of the 24 Americans at the camp, ten had been killed and 11 wounded.The official North Vietnamese history claimed that 400 South Vietnamese troops had been killed and 253 captured. It claimed, however, that only three American advisors were killed during the action.

Colonel Lownds infuriated the Special Forces personnel even further when the indigenous survivors of Lang Vei, their families, civilian refugees from the area, and Laotian survivors from the camp at Ban Houei Sane arrived at the gate of KSCB. Lownds feared that PAVN infiltrators were mixed up in the crowd of more than 6,000. The indigenous soldiers, to the shock of the SOG and CAP personnel, were disarmed and forced to sit, under armed guard, in bomb craters. Without food or water, many of the Laotians turned around and walked back down Route 9 toward Laos.. The Bru were excluded from evacuation from the highlands by an order from the ARVN I Corps commander, who ruled that no Bru be allowed to move into the lowlands. Colonel Ladd, back on the scene, reported that the Marines stated that "they couldn't trust any gooks in their damn camp" There had never been any love lost between the Special Forces personnel and the Marines. General Rathvon Tompkins, commander of the 3rd Marine Division, described the Special Forces soldiers as "hopped up …wretches …[who] were a law unto themselves."

At the end of January, General Tompkins had ordered that no Marine patrols proceed more than 500 meters from the Combat Base. The SOG recon teams however, kept on patrolling, providing the only human intelligence available in the battle area. This, however, did not prevent the Marine tanks within the perimeter from training their guns on the SOG camp.

Logistics and supporting fire

Colonel Lownds estimated that the logistical requirements of KSCB were 60 tons per day in mid-January and rose to 185 tons per day when all five battalions were in place. The greatest impediments to the delivery of supplies to the base were the closure of Route 9 and the winter monsoon weather. From the beginning of the battle until early March, low-lying clouds and fog enclosed the area from early morning until around noon. Even then, the cloud cover rarely rose above 2,000 feet, closing the airfield to all but the most intrepid aviators.

Making matters worse, any aircraft that did brave the weather and attempted to land was subject to North Vietnamese anti-aircraft fire on its way in for a landing. Once the aircraft did touch down, it became the target of any number of PAVN artillery or mortar crews. The aircrew then had to once again brave the anti-aircraft gauntlet on the way out.

The fate of a USMC KC-130F of VMGR-152, provided a typical example of the difficulty in resupplying the firebase. Hit by groundfire during landing at Khe Sanh on 10 February, the fuel bladders aboard were set alight and the airframe burned out on the runway, further obstructing resupply operations. As a result, 65 percent of all supplies were delivered by paradrops from C-130 aircraft. The most dramatic supply delivery system used at Khe Sanh was the Low Altitude Parachute Extraction System (LAPES), in which palletized supplies were pulled out of the cargo bay of a low-flying transport aircraft by means of an attached parachute. The pallet slid to a halt on the airstrip while the aircraft never had to actually land. The Air Force claimed that, during the siege, 14,356 tons of supplies were delivered to Khe Sanh by air (8,120 tons by paradrop). 1st Marine Aircraft Wing records indicated that the unit delivered 4,661 tons of cargo into KSCB.

The resupply of the numerous, isolated hill outposts was fraught with the same difficulties and dangers. The fire of PAVN anti-aircraft units took its toll of helicopters that made the attempt. The Marines found a solution to the problem in the "Super Gaggle" concept. 12 A-4 Skyhawk fighter-bombers provided flak suppression for massed flights of 12-16 helicopters, which would resupply the hills simultaneously. The adoption of this concept at the end of February was the turning point in the resupply effort. After its adoption, Marine helicopters flew in 465 tons of supplies during February. When the weather later cleared in March the amount was increased to 40 tons per day.

As more infantry units had been assigned to defend KSCB, artillery reinforcement kept pace. By early January, the defenders could count on fire support from 46 artillery pieces of various calibers, five tanks armed with 90mm guns, and 92 single or Ontos-mounted 106mm recoiless rifles. The base could also depend on fire support from U.S. Army 175mm guns located at Camp Carrol, east of Khe Sanh. Throughout the battle, Marine artillerymen fired 158,891 mixed rounds. Marine analysis of PAVN artillery fire disclosed that PAVN gunners had fired 10,908 artillery and mortar rounds and rockets into Marine positions during the battle.

Final attacks

On the night of the fall of Lang Vei, three companies of the PAVN 101D Regiment, moved into jump-off positions to attack Alpha-1, an outpost just outside the Combat Base, held by 66 men of the 9th Marines. Under cover of a mortar barrage, the North Vietnamese penetrated the perimeter and pushed the remaining 30 defenders into the southwestern portion of the defenses. For some unknown reason, the PAVN troops did not press their advantage and eliminate the pocket. A relief force set out from the main base and attacked through the North Vietnamese, pushing them into supporting tank and artillery fire.

On 23 February, KSCB received its worst bombardment of the entire battle. During one eight-hour period the base was rocked by 1,307 North Vietnamese rounds, most of which came from 130mm guns, and 152mm artillery pieces located in Laos. Casualties from the bombardment were ten killed and 51 wounded. Two days later, the first PAVN trenches appeared, running due north to within 25 meters of the Combat Base perimeter. That same day, a patrol from Bravo Company 1st Battalion, 26th Marines was ambushed by a PAVN force estimated at battalion-size. Casualties during the contact amounted to nine Marines killed, 25 wounded, and 19 missing and presumed dead.

Marine Corps sniper team searches for targets in the Khe Sanh Valley

At the end of February, American intelligence postulated that the 66th Regiment, 304th PAVN Division was in the process of mounting an attack on the positions of the 37th ARVN Ranger Battalion, on the eastern perimeter. On the night of 28 February, the Combat Base unleashed artillery and airstrikes on possible North Vietnamese staging areas and routes of advance. At 21:30, the attack came on, but it was stifled by the small arms of the Rangers, who were supported by thousands of artillery rounds and air strikes. Two further attacks later in the morning were halted before the North Vietnamese finally withdrew. PAVN, however, was not through with the ARVN troops. Five more attacks against their sector of the defenses were launched during the month of March.

By mid-March, Marine intelligence began to note an exodus of PAVN units from the Khe Sanh sector. The 325C Divisional Headquarters was the first to leave, followed by the 95C and 101D Regiments, all of which relocated to the west. At the same time, the 304th Division withdrew to the southwest. That did not mean, however that battle was over. On 22 March over 1,000 North Vietnamese rounds fell on the base, and, once again, the ammo dump was detonated.

On 30 March, Bravo Company, 26th Marines, launched an attack toward the location of the ambush that had claimed so many of their comrades on 25 February. Following a rolling barrage fired by nine artillery batteries, the Marine attack advanced through two PAVN trenchlines, but the Marines failed to locate the remains of the men of the ambushed patrol. The Marines claimed 115 North Vietnamese killed while their own casualties amounted to ten dead, 100 wounded, and two missing. At 08:00 on the following day, Operation Scotland was officially terminated. Operational control of the Khe Sanh area was handed over to the U.S. Army's 1st Air Cavalry Division for the duration of Operation Pegasus.

Cumulative friendly casualties for Operation Scotland, which began on 1 November 1967, were: 205 killed in action, 1,668 wounded, and 25 missing and presumed dead. These figures do not include casualties among Special Forces troops at Lang Vei, aircrews killed or missing in the area or Marine replacements killed or wounded while entering or exiting the base aboard aircraft. As far as North Vietnamese casualties were concerned, 1,602 bodies were counted, seven prisoners were taken, and two enemy rallied to allied forces during the operation. American intelligence estimated that between 10,000 and 15,000 PAVN troops were killed during the operation. These figures, however, should be considered in light of the methods by which they were obtained. The estimates were almost exclusively gathered by indirect means: sensor readings, sightings of secondary explosions, reports of defectors or POWs, and inference or extrapolation.

Relief and results

Operation Pegasus

Planning for the overland relief of Khe Sanh had begun as early as 25 January 1968 when Westmoreland ordered General John J. Tolson, commander of the 1st Air Cavalry Division, to prepare a contingency plan. Route 9, the only practical overland route from the east, was impassable due to its poor state of repair and the presence of PAVN troops. Tolson was not happy with the assignment, since he believed that the best course of action, post-Tet, was to use his division in an attack into the A Shau Valley. Westmoreland, however, was already planning ahead. Khe Sanh would be relieved and then used as the jump-off point for a "hot pursuit" of enemy forces into Laos.

On 2 March, Tolson presented a briefing and laid out the concept of what became known as Operation Pegasus. The operational plan for what was to become the largest operation launched by III MAF thus far in the conflict, was simple. The 2nd Battalion, 1st Marine Regiment and the 2nd Battalion, 3rd Marines Regiment would set out from Landing Zone Stud at Ca Lu (16 kilometers to the east of Khe Sanh) and head down Route 9 while elements of the 1st Air Cavalry leapfrogged by helicopter down the road, air-assaulting onto key terrain features to cover the Marine advance. The advance would be supported by the fire of 102 pieces of artillery. The Marines would be accompanied by their 11th Engineer Battalion, which would repair the road as the advance moved forward. Later, the 1st Battalion, 1st Marine Regiment and 3rd ARVN Airborne Task Force (the 3rd, 6th, and 8th Airborne Battalions) would join the operation.

General Westmoreland's planned relief effort infuriated the Marines, who had not wanted to hold Khe Sanh in the first place and who had been roundly criticized for not defending it well. The Marines had constantly argued that technically, Khe Sanh had never been under siege, since it had never truly been isolated from resupply or reinforcement. General Cushman was appalled by the "implication of a rescue or breaking of the siege by outside forces."

Regardless, on 1 April, Operation Pegasus began. Opposition from the North Vietnamese was light and the only problem that hampered the advance was continual heavy morning cloud cover that slowed the pace of helicopter operations. As the relief force made progress, the Marines at Khe Sanh moved out from their positions and began patrolling at greater distances from the base. Things heated up for the air cavalrymen on 6 April, when the 3rd Brigade encounterd a PAVN blocking force and fought a day-long engagement.

On the following day, the 2nd Brigade of the 1st Air Cavalry captured the old French fort near Khe Sanh village after a three-day battle. The link-up between the relief force and the Marines at KSCB took place at 08:00 on 8 April, when the 2nd Battalion, 7th Cavalry entered the camp. The 11th Engineers proclaimed Route 9 open to traffic on 11 April. On that day, General Tolson ordered his unit to immediately make preparations for operations in the A Shau Valley. At 08:00 on 15 April, Operation Pegasus was officially terminated. American casualties amounted to 92 killed in action, 667 wounded, and five missing. 33 South Vietnamese troops were also killed and 187 wounded. Estimates of PAVN casualties were 1,100 killed and 13 captured.

Colonel Lownds and the 26th Marines departed, leaving the defense of the base to the 1st Marine Regiment. General Westmoreland continued to demand that the base be occupied and kept it so until he departed Vietnam on 11 June. His successor, General Creighton Abrams allowed the passage of one week before he ordered the initiation of Operation Charlie, the destruction and evacuation of KSCB. That task was completed on 6 July. Victory in Vietnam relates ever an increasing intensity of PAVN attacks on the Combat Base, during which "1,300 American troops were killed and 34 aircraft were shot down." Colonel Lownds made his final appearance in the story of Khe Sanh on 23 May, when he and his regimental sergeant major stood before President Johnson and were presented with a Presidential Unit Citation on behalf of the 26th Marines.

Once the news of the closure of the KSCB was announced, the American media immediately raised questions about the reasoning behind its abandonment. If Khe Sanh had been so strategically important in January, why was it not so in July? The explanations given out by the Saigon command were that

"the enemy had changed his tactics and reduced his forces; that PAVN had carved out new infiltration routes; that the Marines now had enough troops and helicopters to carry out mobile operations; that a fixed base was no longer necessary."

By this point in the conflict, however, the Marine demand for more mobility was moot. The gradual withdrawal of U.S. forces begun during the following year and the adoption of Vietnamization meant that, by 1969, "although limited tactical offensives abounded, U.S. military participation in the war would soon be relegated to a defensive stance."

Riddle of Khe Sanh

See also: Vietnamese Communist grand strategy

The precise nature of Hanoi's strategic goal at Khe Sanh is one of the most intriguing unanswered questions of the Vietnam War. This perplexing problem, known among historians as the "riddle of Khe Sanh" can be best summed up by John Prados and Ray Stubbe: "Either the Tet offensive was a diversion intended to facilitate PAVN/NLF preparations for a war-winning battle at Khe Sanh, or Khe Sanh was a diversion to mesmerize Westmoreland in the days before Tet."

Was PAVN actually planning a genuine attempt to take Khe Sanh? Was the battle truly an attempt to replicate the Viet Minh triumph against the French at the Battle of Dien Bien Phu? General Westmoreland thought so. That belief was the basis for his desire to stage "Dien Bien Phu in reverse". If Hanoi was willing to mass its troops within a limited geographic area, making it vulnerable to American firepower, then so much the better in his opinion.

Why else would Hanoi have committed so many forces to the area instead of committing them to the Tet Offensive? The North Vietnamese only committed about half of their available forces to the offensive (60–70,000), the majority of whom were members of the NLF. Were the forces around Khe Sanh simply a localized defensive measure in the DMZ area?

General Abrams has also suggested that the North Vietnamese may have been planning to emulate Dien Bien Phu. He believed that PAVN's actions during Tet proved it. It would have taken longer to dislodge the North Vietnamese at Huế if PAVN had committed the three divisions at Khe Sanh to the battle there (although PAVN did commit three regiments to the fighting from the Khe Sanh sector).

Another interpretation was that the North Vietnamese were planning to work both ends against the middle. This strategy has come to be known as the Option Play. If PAVN could take Khe Sanh, all well and good. If they could not, they would occupy the attention of as many American and South Vietnamese forces in I Corps as they could in order to facilitate the Tet Offensive. This view was supported by a captured (in 1969) North Vietnamese study of the battle. According to the study, PAVN would have taken Khe Sanh if they could, but there were limits to the price they were willing to pay. Their main objectives were to kill American troops and to isolate them in the remote border regions.

General and historian Dave Palmer suggests "General Giap never had any intention of capturing Khe Sanh … [it] was a feint, a diversionary effort. And it had accomplished its purpose magnificently."This is also the position taken in the official PAVN history, but which offers no further explanation of the strategy.

Marine General Rathvon M. Tompkins, commander of the 3rd Marine Division, has pointed out that had PAVN actually intended to take Khe Sanh, North Vietnamese troops could have cut the Combat Base's sole source of water, a stream 500 meters outside the perimeter of the base. Had they simply contaminated the stream, the airlift would never have been able to provide enough water to the Marines. Marine Lieutenant General Victor Krulak seconded the notion that there was never a serious intention to take the base by also arguing that neither the water supply nor the telephone land lines were ever cut by the North Vietnamese.

One argument leveled by Westmoreland at the time (and often quoted by historians of the battle) was that only two Marine regiments were tied down at Khe Sanh compared with several PAVN divisions. But, at the time Hanoi made the decision to move in around the base, Khe Sanh was held by only two (or even just one) American battalions. Was the destruction of one battalion to be the goal of two to four PAVN divisions? Yet, even if Westmoreland believed his statement, his argument never moved on to the next logical level. By the end of January 1968, he had moved half of all U.S. combat troops — nearly fifty maneuver battalions — to I Corps.