“When you’re at Khe Sanh, you’re not really anywhere,” Marine Brigadier General Lowell English once declared. “You could lose it and you haven’t lost a damn thing.” The Marines were not interested in Khe Sanh and did not want to try to defend the large, unpopulated and jungle-covered expanse that spread out west of Camp Carroll and into Laos. But General William Westmoreland, the overall U.S. commander, disagreed with that assessment. Westmoreland saw Khe Sanh as the potential westernmost anchor of his, and therefore the Marines’, northern defensive line. Defending it when the time came, during the siege in early 1968, required extraordinary use of air power.
United States Marines in I Corps Tactical Zone (I CTZ) saw their mission as defense of the border with North Vietnam and the major cities sector. The northernmost Marine defense paralleled the Cua Viet River just south of the Demilitarized Zone and extended inland some 30 miles, with major bases at Dong Ha, Quang Ngai and Quang Tri. The line then bent south and ended at two artillery firebases, the Rockpile and Camp Carroll. Twenty miles farther southwest, along the connecting overland artery Route 9, was Khe Sanh, just seven miles from Laos.
In the spring of 1966 when the Marines moved into Khe Sanh, the Army’s Special Forces abandoned their base there and moved seven miles west on Route 9 to a new position at Lang Vei. The Marines inherited what would come to be called the Khe Sanh Combat Base, situated on a 300-foot plateau above the countryside to the east and south. To the west and north, the base was surrounded by gradually sloping hills that rose 1,000 feet above it. Route 9 ran just below the base, and two miles away was Khe Sanh with its 1,500 inhabitants.
Khe Sanh Combat Base originally had a 1,900-foot runway suitable for light aircraft, small transports and helicopters. After the Marines took over, the strip was expanded to 3,900 feet of hard-surface aluminum planking. The runway ran on an east-west axis, with a cargo area within the last 1,000 feet of the west end. The addition of radar and a Tactical Air Navigation system made instrument landings possible.
Beginning in April 1967, patrols from Khe Sanh Combat Base came under ambush northwest of the base. Into July the Marines engaged in a series of battles—known as the “Hill Fights”—for control of the heights with regular, battalion-sized units of the North Vietnamese Army (NVA). The Marines secured Hill 861 three miles north of the base, and, another half-mile beyond, the twin peaks of Hills 881 South and 881 North. The Marines soon abandoned Hill 881N, but Hill 881S was particularly vital to the defense of the base because it was just off the axis of the runway and overlooked the entire complex.
The tops of Hills 861 and 881S were cleared of foliage and transformed into firebases, each with a 75×150-yard mined and barbed-wire perimeter, cleared fields of fire 200 to 300 meters down the hill, a helipad and garrisons of from 200 to 600 Marines. Hill 881S also mounted three 105mm howitzers whose range covered Khe Sanh Combat Base and Hill 861.
By late summer, two battalions and the regimental headquarters of the 26th Marines, 3rd Marine Division were at Khe Sanh. Colonel David Lownds, commander of the 26th, was the overall base commander. In August and September, the NVA cut off Route 9 and increased its offensive activity throughout I Corps; during the last two months of 1967, it increased patrol and supply activity around Khe Sanh. United States intelligence estimated that elements of two or more NVA divisions were in the area, totaling possibly 20,000 men.
On January 2, 1968, six NVA officers in American uniforms were killed at the wire outside the combat base while reconnoitering its perimeter. The intelligence estimate of NVA troops in the area was raised to possibly 50,000. General Westmoreland directed planning to ensure mass air support should the base be attacked. Some 250 sensors with electro-chemical, seismic, infra-red and acoustic heads were sown by air around the combat base. The sensors hung in trees, buried themselves in the ground or were camouflaged in deep vegetation and surrounded by mini-minefields. Although not accurate enough for individual target designations, they did provide warning and area identification of enemy troop and supply movements.
By January 10, the Marines at Khe Sanh had dug firing positions next to their above-ground tents and bunkers and were busy improving their barbed-wire defenses and minefields. Helmets, flak jackets and gas masks became mandatory wear when the North Vietnamese began regularly shelling the base with artillery. Within the next week, some 1,000 reinforcements were inserted into the base, as more patrol contacts were made with enemy forces. On January 20, a surrendering NVA lieutenant revealed that the base would be attacked that night.
Just after midnight a barrage of mortars, rockets and artillery broke over the firebase on Hill 861. The fire strike gave way to a ground attack of some 300 North Vietnamese Army troops, who opened a 75-meter-wide gap through the perimeter wire in heavy fog. The attackers penetrated to the helicopter pad at the center of the compound, but were then hit by a counterattack supported by mortar fire from Hill 881S. A second assault followed, and the Marines used flares, tear gas and hand-to-hand combat to drive off the enemy. Only minutes after the attack on Hill 861, the North Vietnamese launched a barrage against the main base. A 122mm rocket hit the combat base ammunition and fuel dump. The 1,500 tons of ammunition produced a massive explosion that spewed tear gas and hot, unexploded rounds all over the base. Shortly afterward, the NVA attacked the village of Khe Sanh, which it took later the same day.
The shelling had destroyed 98 percent of the ammunition stocks on the Khe Sanh base, killed 18 Marines and wounded 40. The runway was cut to 2,000 feet of useable length, and one helicopter was destroyed. Six helicopter parking revetments that adjoined the runway also were destroyed. When asked to report on the situation, Colonel Lownds replied that it was “critical, to say the least.” Lownds estimated that he would need a resupply of 160 tons per day to maintain his position. Within the base itself, the defenses were hurriedly reinforced and the tents and above-ground structures gave way to trenches and dug-in bunkers. The siege of Khe Sanh had begun and would continue for 77 days, lasting until April 8, 1968.
A daily routine began to evolve. Each morning the base was shelled as daylight approached. Random bombardments of rockets, mortars and artillery continued throughout the day. Once night fell, a creeping barrage started on the west end of the runway and worked its way eastward. The number of rounds fired daily ranged from fewer than 100 to several hundred. Any major activity on the base, such as landing aircraft or construction, brought down immediate fire.
The North Vietnamese Army sited heavy mortars and 122mm rockets in the deep foliage surrounding Khe Sanh on all sides, including Hill 881N. They had 130mm and 152mm artillery positioned in caves in the mountains of Laos some 15 miles away. The big guns rolled out of the caves to fire and then withdrew into them to avoid counter-battery fire or air attack. The guns in Laos were beyond the range the U.S. artillery and were never silenced during the course of the siege. The Marines on the base had five to 18 seconds’ warning for most incoming artillery rounds. If a mortar was sighted as it fired, they had up to 22 seconds, but there was no warning except the sound of the incoming round if the firing was not sighted.
Fully reinforced after the January 21 attacks, Khe Sanh had 6,500 troops including those in the overlooking hills. The force consisted of five Marine battalions, one ARVN ranger battalion and assorted support elements. The base’s 21 vehicles included a few tanks and 10 M-50 Ontos antitank vehicles. The Marines had six 4.2-inch mortars, 18 105mm howitzers, six 155mm howitzers and 90 106mm recoilless rifles—which included the 60 mounted on Ontos. The artillery could initiate counter-battery fire against an incoming round’s firing position within 40 seconds. The base was also covered by artillery fire from the 16 M-107 self-propelled 175mm guns at the Rockpile and Camp Carroll.
The base defenders surfaced from their dugouts and bunkers each morning at first light, and did as much as they could in the four to five hours during which fog blanketed the area and screened them from NVA observation. They then hunkered down the remainder of the day, except when it was absolutely necessary to move about. At night they came out and warily accomplished needed tasks. Both sides used night vision devices.
Throughout the siege, the North Vietnamese Army made several attempts to storm one of the major outposts or the main base itself, but such attacks were widely spaced. At the end of January, 45 B-52s bombed a suspected NVA headquarters in Laos that had been identified through radio intercepts. Soon afterward the airstrip, which had been closed to C-130 use, was reopened. On February 5 the NVA launched an attack against Hill 861. The battalion-size assault was beaten back by a fierce counterattack; artillery and air strikes broke up a follow-on attack by a second battalion.
On February 7, the Lang Vei Special Forces camp was attacked and overrun. The next day, just after dawn, a forward observation post 500 meters west of the Khe Sanh Combat Base perimeter was overrun but was retaken by a Marine relief force heavily supported by fighter aircraft. Three days later a Marine C-130 carrying a load of helicopter fuel bladders was hit by ground fire, broke in half and exploded, killing or fatally wounding eight on board. A second C-130 was damaged on the ground later the same day, leading to the suspension of C-130 landings, but C-123s and helicopters continued to operate from the strip.
On February 23, the base took a record 1,307 incoming rounds, one-third of them fired by North Vietnamese artillery. Two days later, Marine patrols located enemy trenches approaching the perimeter. On the 29th, the NVA launched three unsuccessful attacks against the South Vietnamese Ranger battalion defending the eastern end of the perimeter. Prior to the attacks, with remote sensors indicating a buildup, artillery, fighter aircraft and B-52s hit the assembly areas and possibly broke up what was to have been a major assault.
As the weather around Khe Sanh improved in March, NVA trenches approaching the perimeter began to form Ts, creating jumpoff points for a forthcoming attack. At the same time, probes and sniping against the base increased. On March 1, two C-123s were destroyed on the ground by shellfire, and five days later a C-123 was hit by groundfire while on a go-around from an aborted landing, killing all 49 on board. A Marine helicopter also crashed shortly thereafter, killing all 22 aboard.
The shelling of the base continued unabated through the second week in March, but other North Vietnamese Army activity, including probes, sniping and trench digging, significantly decreased. By the end of the month a reduction in enemy forces was confirmed and the Marines reinitiated aggressive patrolling. A three-hour firefight on March 30 was the last major ground combat action of the siege.
On April 1, the U.S. Army’s 1st Cavalry Division Airmobile launched Operation Pegasus to lift the siege and open Route 9. The NVA mounted only light resistance to the advance for several days and then ceased all opposition. Fresh South Vietnamese forces were airlifted into Khe Sanh Combat Base on April 6, followed by elements of the 1st Cavalry Division two days later.
The distinctive feature of the siege of Khe Sanh was the overwhelming firepower that the U.S. forces directed against the North Vietnamese Army. Estimates place the total number of enemy shells fired at 25,000 to 30,000 rounds in 77 days. The U.S. return fire from batteries at the base and from the Rockpile and Camp Carroll totaled some 150,000 rounds. Added to the artillery firepower was the weight of munitions dropped by aircraft. High-flying B-52s, guided by ground radar and flying in V-shaped formations of three aircraft, appeared daily over Khe Sanh. Each formation dropped 75 tons of 500-pound bombs and saturated an area 1⁄2 mile wide by 11⁄2 miles long.
During the siege, the U.S. Air Force flew an average of 11 three-plane B-52 formations per day, and Air Force, Marine and Navy fighter aircraft averaged some 300 attacks daily. Two-thirds of the fighters dropped bombs or napalm under radar direction from the base. Night bombing runs were conducted using flares, and the night skies around the base were patrolled by AC-47 and AC-130 gunships armed with cannons and miniguns.
The NVA knew the B-52s were restricted from dropping within a mile of friendly forces, so at night they tried to move at least that close to the perimeter. When, on February 29, the B-52s reduced the stand-off distance from the perimeter to one-half mile, the result was the decimation of an NVA two-battalion attack force. During the course of the siege, the U.S. Air Force dropped five tons of bombs for each of the estimated 20,000 attacking NVA troops.
If firepower determined the outcome of the fight, it was airlift that allowed the defenders to hold their positions. Since late in 1967, Khe Sanh had depended on airlift for its survival. When the siege began on January 21, the loss of the main ammunition dump and the cutting of the runway threatened disaster, but that same day, despite bad weather, C-123s airlanded four tons of supplies and C-130s began airdrops, while Marine helicopters took the wounded off the hilltop firebases.
From the very beginning, helicopter support was crucial. When they could no longer be based at Khe Sanh Combat Base, helicopters operated from Dong Ha and other nearby locations. Throughout the siege, they braved enemy fire on approach and departure as well as mortar, rocket and artillery fire when on the ground. They augmented the fixed-wing aircraft in supplying the main base and were vital in rotating personnel and evacuating the wounded. Helicopters provided the only direct support to the hilltop firebases, bringing in all supplies, including precious trailer loads of water. Seventeen helicopters went down during the siege and another 35 were badly damaged. Using primarily Marine CH-46s and CH-53s, most of the resupply missions were flown using external slings with up to two tons of cargo in each net. Fully aware of being easy targets, the helicopter crews were limited to as little as 19 seconds’ hover time for their deliveries. Beginning in late February until the end of the siege, supply helicopters flew in formations of 12—called Super Gaggles—escorted by fighters and helicopter gunships. During bad weather the crews used flares, smoke and multiple descents to find their designated landing zones.
Without control of the hills, Khe Sanh might have turned into another Dien Bien Phu, and without the helicopters the hill firebases could not have survived.
An average of 155 tons of supplies was landed or dropped each day of the siege. Thirty-five percent of the tonnage was landed, with C-130s delivering 60 percent of that amount and C-123s, with their shorter landing roll, bringing in the rest. The C-123s carried three- to five-ton loads, while the larger C-130s delivered 10 to 15 tons per sortie. Both aircraft had floor-roller assemblies and palletized cargo systems for rapid on- and off-load and were capable of flying multiple sorties per day. Cargo reload points included Saigon and Bien Hoa to the south, and the nearby airlift depot at Da Nang, only a 30-minute flight from Khe Sanh.
The normal approach to the Khe Sanh runway was from the east, which was facilitated by instrument approach to touchdown. But the eastern approach was directly over NVA-held territory and left the aircraft vulnerable to intense groundfire both coming and going. The NVA at Khe Sanh had no SAMs or high-velocity/high-altitude/radar-guided guns, but the volume of fire from handheld and crew-served weapons was stil formidable. Two C-123s and one C-130 were lost during the siege.
The crews used the eastern approach whenever the weather screened the aircraft from groundfire. Otherwise, the transports made a sharply turned, steeply banked, short downwind visual approach to the western end of the runway. The groundfire was less, but so was the terrain clearance.
All aircraft crews landing at Khe Sanh knew they could be the target of enemy small arms and indirect fire while sitting on the ground. Accordingly they minimized the ground times. Whenever possible, landing crews immediately turned off the runway into the cargo loading area. They maintained a slow taxi through the cargo area while simultaneously rolling the cargo pallets onto the ramp behind them. They then taxied back onto the runway for takeoff over the same end, but in the opposite direction from which they had arrived. The shorter-landing C-123s accomplished this routinely but the C-130, with its longer landing roll, usually had to add a 180-degree turn on the main runway. Ground times for landing, offloading, taxiing and takeoff ran on the order of three minutes. Once airborne, the aircraft maintained a hard turn and steep climb to the northwest. One crewman noted, “There was no feeling in the world as good as being airborne out of Khe Sanh.” Passengers on such flights sat on their flak jackets so as not to take home a rear-embedded souvenir.
Enemy fire ended the C-130 landings and might have threatened the survival of Khe Sanh Combat Base. However, within three days of the February 13 decision that C-130s would no longer be allowed to land at the base, the Air Force started delivering C-130-size loads using both conventional airdrops and the low altitude parachute extraction system (LAPES). During this type of delivery, the aircraft made an approach to the eastern end of the runway under visual conditions, staying five to 20 feet off the ground at an airspeed of 130 knots. An extraction chute pulled the multi-pallet, interlocked load out of the aircraft. The last pallet landed first and then skidded down the runway. The runway required replacement of aluminum planking after a LAPES delivery, but the base continued to receive heavyweight and large-size cargo resupply.
The Air Force flew 37 LAPES deliveries into Khe Sanh, but it took some tragic experiences to get it right. The first attempt was a disaster as a chute malfunctioned and the load skidded into a medical station, killing three Marines. Three weeks later, the second such delivery was off-center and killed one Marine when the load hit a bunker. Following that, the Air Force changed the delivery procedure to a ground proximity extraction system (GPES), which used a hook dangling from the open ramp of the plane to engage a ground-embedded wire stretched across the runway—much like a Navy carrier landing. Of the 15 GPES deliveries made, two malfunctioned.
On the western end of Khe Sanh Combat Base and 500 meters west of the perimeter, a drop zone 750 meters long by 500 meters wide was established. Some 600 airdrops were made during the siege, 90 percent by C-130s and the rest by C-123s. All the drops were made in daylight but nine out of ten of them were made in bad weather with only a 3 percent malfunction rate.
The majority of the drops were made using the container delivery system. Instead of using chutes to extract large palletized loads, this system consisted of 1-ton loads, each with its own small chute. Each load was bundled or clustered with others and held in the aircraft by a gate. The drop altitude was 400 to 600 feet above the drop zone. The gate was cut at load release, while at the same time the pilot pulled a nose-up maneuver, causing the bundles to exit the aircraft by gravity. Rather than hanging in the air and drifting long distances in the wind, the load swung only once before touching down.
The airlift effort in the siege of Khe Sanh demonstrated what a well-trained, properly sized and equipped airlift force can do. The combination of aircraft and helicopters allowed U.S. forces to meet all of the varied requirements to keep Khe Sanh operating, despite the exceptionally hazardous conditions resulting from loss of runway length, enemy groundfire and continually bad weather. Historically, tactical airlift under siege conditions has had a very limited record of success. However, it worked at Khe Sanh.I
William A. Barry graduated from the U.S. Air Force Academy and spent 20 years in the Air Force as a C-130 navigator, war planner and NATO intelligence officer. For additional reading, see: Khe Sanh: Siege in the Clouds, by Eric Hammel; and The End of the Line: The Siege of Khe Sanh, by Robert Pisor.
This article was written by William A. Barry and originally published in the October 2007 issue of Vietnam Magazine. For more great articles, subscribe to Vietnam magazine today!
