Air Power On Trial: The Siege of Khe Sanh

Khe Sanh Sky Crane

Khe Sanh Sky Crane

Some battles become symbols after they happen: Gettysburg as the high tide of the Confederacy or Pearl Harbor for treacherous surprise or Midway as a turning point. One battle in Vietnam had an implicit symbolism before it was fought: the siege of Khe Sanh.

The dream of General Vo Nguyen Giap and other North Vietnamese leaders was to do to the United States at Khe Sanh what they had done to France at Dien Bien Phu. There they had cut off a sizeable force, placed it under siege, forced it to surrender and thus brought about the end of the war. They hoped to do the same at Khe Sahn.

The Difference at Khe Sanh

The U.S. leaders, particularly General William C. Westmoreland, anticipated General Giap’s desire to repeat his triumph, and decided that any such attempt by the North Vietnamese could be turned into a massive U.S. victory by the use of overwhelming air power. In Westmoreland’s view, the enemy forces attempting to overrun Khe Sahn could be trapped in a place where repeated bombing attacks would inflict huge numbers of military casualties yet harm only a minimum number of civilians. He based his optimism in part on the successful defense of Con Thien in September, 1967, when U.S. air and artillery support had driven off an attack on a Marine outpost by large North Vietnamese forces.

Before The Battle

The Khe Sanh Combat Base had been an Army Special Forces base as early as 1962. Located in Quang Tri province in the northwest part of South Vietnam, it was about ten miles from Laos and fifteen from the line marking the demi1itarized zone. A small village of the same name was located about two miles a way, while the U.S. Special Forces camp of Lang Vei was five miles distant.

The combat base was located in the center of four valley corridors and was surrounded by tall, forested hills, some as high as 4,000 feet. The base itself was sited on a flat plateau and was about a mile long and one-half mile wide. The laterite soil was good for digging trenches and bunkers. These would serve well as the North Vietnamese poured in an average 2,500 shells per week on the base. Unfortunately, the soil was a poor foundation for the airstrip. The original 1,500 foot French runway had been extended to 3,900 feet and covered with aluminum mats. These rolled and pitched when the ground became soaked. They were displaced by the hard-landings caused by the need to make high speed, high rate of descent approaches and were turned into tire-piercing angles when torn by shell fire.

The runway sat on an eight-hundred foot rise, which made approaches from the east difficult because of a lack of visual references. During the winter and early spring, visibility was usually less than three miles, with a ceiling of a thousand feet or less. Conditions improved as the day warmed.

During late 1967 and early 1968, the United States began to increase the forces at Khe Sanh, ostensibly to interrupt Communist troop movements, but in fact to bait the trap. The base could accommodate only about 6,000 troops, initially three battalions of the 26th Marine Regiment. These were later reinforced by a battalion from the 9th Marine Regiment and the 37th ARVN Ranger battalion. Unlike the French at Dien Bien Phu, the Marines made sure they held the high ground and were supported by sixteen of the Army’s huge 175 mm cannon, all placed to deliver accurate fire.

The North Vietnamese responded exactly as Westmoreland expected, ultimately bringing in two full regular divisions, the 304th and 325thC—a total of about 23,000 troops. They were well equipped with heavy artillery including the effective Soviet-made 130 and 152 mm artillery and 122 mm rockets. In effect, the enemy re-fought the battle of Dien Bien Phu with the same equipment and the same tactics, seeking to tighten the noose around the base and then shelling it with artillery, rockets and mortars. Unfortunately for them, the United States was going to fight a war with far more equipment and with much more advanced technology than the French had possessed.

The Battle Begins

The Battle of Khe Sanh began on January 21, 1968 with inconclusive ground action by both U.S. and North Vietnamese patrols. The requirement for aerial re-supply was made crucial on the first day when one of the big rockets scored a direct hit on the main Marine ammunition dump, destroying 1,500 tons of high explosives, no less than 98 percent of available ammunition. It was a bad beginning to a long 77 day siege.

The decision to permit the enemy to surround Marine forces at Khe Sahn had been based upon Westmoreland’s confidence in air power. An air campaign, Operation NIAGARA, had been prepared for the concentrated use of Air Force, Marine and Navy planes to destroy the enemy. The plan had two phases: identifying targets before the battle began and conducting a full scale response by artillery and air power once it started.

Westmoreland as the commander, U.S. Military Assistance Command, Vietnam, nominally had emergency powers that would have permitted him to give General William W. “Spike” Momyer total control over all aircraft in the operation. Momyer was ideally positioned for the task, being Westmoreland’s deputy commander for air and also commander of Seventh Air Force. But, acceding to the traditional Marine desire to have their own aircraft operate in the close air support role, Admiral U.S. Grant Sharp, Jr. Commander-in-Chief, Pacific refused to permit a unified command. Instead, Momyer was given authority to “direct and coordinate” air operations, with the Marines supplying any “excess assets” for his use. The de facto result was the creation of six zones around Khe Sanh. The Marines designated the four zones closest to the base for their operations, while the two most distant zones were allotted to the USAF.

Despite this rebuff, Momyer set about the task of interdicting enemy supplies, in effect “besieging the besiegers” and bringing the maximum amount of firepower on the entrenched enemy. He used the full weight of Air Force capability, beginning with a centralized intelligence center at Tan Son Nhut. There some 200 people tracked the enemy to optimize both air and artillery attacks. More than 250 ACOUSID (Acoustic/Seismic Intrusion Detectors) and ADSIDS (Air-Delivered Seismic Intrusion Detectors)-sensors were installed around Khe Sanh to detect enemy movements. Information was sent from the sensors to an orbiting Lockheed EC-121, which relayed the data to the intelligence center at Nakhon Phanom in Thailand. The data were used for both air strikes and artillery shoots.

Momyer also provided a C-130 Airborne Battlefield Command and Control Center to coordinate aerial attacks and artillery bombardment. It was incorporated into the Khe Sanh fire support coordination center. Working together, the ground and air centers were able to coordinate USAF, Navy, Marine and even Army tactical air efforts with the Arc Light B-52 operations and artillery shoots.

The arrangement worked well for the Marines at Khe Sanh, but Air Force leaders felt that it failed to optimize the situation for all of South Vietnam, and continued to press for a centralized control. They finally achieved their objective on March 21, when the battle was largely won, and more than 87 percent of all sorties in the siege had already been made. It was, nonetheless, a step in the right direction.

A Niagara of Bombs

Westmoreland had counted on a “Niagara” of bombs falling upon the enemy, and his wishes were fulfilled. The B-52s had initiated the bombing campaign a week before the siege had begun, with 94 sorties against twelve North Vietnamese targets. The immediate response to the North Vietnamese attack came on January 22nd with B-52 attacks on four targets. The next day, attacks by Marine, Navy and Air Force tactical aircraft started. Within a week, more than 3,200 sorties had been flown, including 200 by B-52s. Over the course of the siege, the B-52s would average 35 sorties per day; Air Force and Marine tactical aircraft would average 300 sorties per day. Two Combat Skyspot radar units were committed to the battle to fine-tune the B-52 drops. The first strikes were made at a distance the Marines considered comfortable; they would soon grow closer.

A nine B-52 mission on November 12, 1967 againt Con Thien had revealed an enemy trick. Knowing that the B-52s provided a three kilometer safety zone around friendly forces, the North Vietnamese began moving ammuniton stores into the area, near the American defensive perimeter. A bomb dropped accidentally within the Con Thien safety zone had set off a series of secondary explosions—and given American planners food for thought.

A series of tests, involving two Skyspot stations to ensure safety, proved that the B-52s could deliver their devastating bomb loads much closer to the defensive perimeter. The first four raids at Khe Sanh resulted in many secondary explosions and fires in the area near the defensive perimeter, proof that the enemy was still using his safety zone tactics. The close-in attacks became regular practice and led General Westmoreland to say that “the thing that broke their backs was basically the fire of the B-52s.”

The effectiveness of the B-52 effort had been improved by the new “Bugle Note” tactics, adopted on February 15, 1968. A grid system of 1 by 2 kilometer blocks was overlaid the target area—the dimensions representing the amount of territory a drop from a single cell of three B-52s could saturate. When the procedure was implemented, six B-52s would arrive every three hours, to be directed to a particular block by the Combat Skyspot controllers. It had a devastating effect upon North Vietnamese troops, comparable to the shattering artillery barrages of World War I.

By the end of the siege, the B-52s had flown 2,548 combat sorties and dropped 59,542 tons of bombs. The number of casualties inflicted on the North Vietnamese was impossible to determine, but it was a significant proportion of their overall losses.

Tactical Aircraft

Not withstanding disputes at headquarter level, the tactical aircraft of the Air Force, Marines and Navy worked in harmony at Khe Sanh, despite the number of aircraft employed (about 500), the wide variety in types and disparities in performance. The controllers had to handle everything from Cessna O-1s to McDonnell F-4s along with continuous streams of transport aircraft. Tactical aircraft from all services dropped more than 40,000 tons of ordnance in just under 22,000 sorties. This effort was augmented by as many as 200,000 rounds from artillery pieces and mortars. Forward air controllers made more than 1,000 sorties, while almost 1,400 reconnaissance missions were flown.

The coordinated combination of B-52, tactical aircraft and artillery slaughtered the North Vietnamese troops despite their bunkers and trenches, and they began withdrawing from the area in mid-March. By April 8, the U.S. Army’s 1st Cavalry Division had linked up with Khe Sanh, which was soon being reached by road traffic.

Yet destroying the enemy had been only half-the battle. The other half required the U.S. forces to stay alive and keep fighting, and to do that, they needed an average of 165 tons of men and materiel brought in every day.

Lifeline in the Sky

The loss of the ammunition dump on the opening day of the battle had created an immediate requirement to replenish ammunition. The 834th Air Wing rose to the task. Despite increasingly heavy anti-aircraft fire, Lockheed C-130 Hercules and Fairchild C-123 Providers landed at Khe Sanh, replenishing the artillery stocks and bringing out the wounded. During the first eight days, an average of 250 tons per day was brought in. The total was supplemented by Marine KC-130 deliveries and by the heavy use of the Boeing Vertol CH-46 Sea Knight helicopters.

The enemy continued to shell the air-strip even as he built up his anti-aircraft strength. Transports were fired at all during their approach to landing. Passive tactics using cloud cover and steep descents were adopted. As soon as an aircraft touched down it became a “mortar magnet”, a target for both artillery and mortars. The C-123s were able to make the turn-off into the parking ramp, but the C-130s had to go to the end of the runway and then taxi back, sometimes being tracked by mortar shells all the way. Both air and ground crews worked feverishly as unloading techniques were speeded up, with the airplanes literally taxiing out from under their palletized cargo.

The C-130s were tough, taking hits, making repairs, taking more hits and still managing to takeoff. On February 5, a C-130E was blasted by machine gun fire that ignited the wooden boxes ammunition boxes it was carrying. The aircraft commander, Lt. Colonel Howard M. Dallman, cooly backed the airplane to the end of the runway, where it would do the least damage if it blew up, then set about putting out the fire. As the crew off-loaded the ammunition, the C-130 was struck again several times, with a tire being destroyed. After an improvised tire change, Dallman was taxiing out for takeoff when another mortar exploded, knocking out an engine. Undaunted, Dallman was preparing a three-engine takeoff from the 3,900 foot strip when the damaged engine was restarted. The plane took several more strikes, but Dallman managed to take off and get back to base. He was the first transport crewman to receive an Air Force Cross.

Many other 130s were damaged, sometimes while being repaired from previous mortar rounds. The only Hercules to be lost was a Marine KC-130 carrying fuel bladders, one of which burst into flames as the aircraft was on final approach. The plane rolled down the runway, racked by explosions, and was completely burned out, with a loss of two crewmen and four passengers.

On February 12th, C-130 landings were suspended, with the smaller C-123s and de Havilland C-7A Caribous being used instead. Three of the C-123s would be lost, one carrying 49 people. It was the single largest loss of life of the entire battle.

Forbidden to land, the C-130s continued their efforts by parachuting containers into the camp, using the Marine ground controlled approach equipment to signal when to drop. The method proved to be effective with only three out of six-hundred containers being lost. The Low Altitude Parachute Extraction System (LAPES) was also used with some success although the delivery method could be hazardous both to air and ground personnel. In early March, tests were made with a ground proximity extraction system (GPES) in which the delivery aircraft fitted with a hook contacted a cable stretched near the ground. The hook engaged the cable, and the loads were pulled out of the aircraft. GPES proved to be well suited to the Khe Sanh environment, and was far less hazardous than LAPES.

The drop zone was the most dangerous area in Khe Sanh; crews had to scramble in the open under fire to get the equipment out of the area, wrestling damaged pallets by hand when forklifts, so often in short supply, were unavailable.

Yet the air supply of Khe Sanh was entirely successful; at no time were food, fuel or ammunition stocks near depletion. By the end of the siege, the transports had completed 1,128 missions and delivered 12,430 tons of supplies. The supply effort had been made somewhat easier by an inexplicable factor; the Communists did not divert or poison the river from which the base drew its water. Had they done so, the tonnage requirements would have risen to accommodate supplying water.

Tet: Diversion and Delusion

Even as the battle at Khe Sanh built in intensity, the North Vietnamese launched their surprise Tet offensive throughout South Vietnam on January 30th. More than 80,000 North Vietnamese Army and National Liberation Front soldiers attacked South Vietnamese military positions, government buildings and cultural centers. Despite the intense fighting throughout the length and breadth of Vietnam, the U.S. support of the forces at Khe Sanh did not waver.

The argument has been advanced that Giap did not intend to take Khe Sanh, using it instead as a diversionary effort to distract U.S. forces from the Tet offensive. He undoubtedly recognized the value of the siege as a diversion, but there is no question that North Vietnamese forces would have overrun Khe Sanh if they had possessed the capability to do so. Giap’s losses were severe, with as many as 15,000 killed, while there were less than 300 American fatalities.

In the end, Westmoreland was correct: U.S. air power, operating for part of the time under centralized control, turned the siege of Khe Sanh into a clear American victory. Giap had made two basic mistakes. First, he had underestimated the effectiveness of U.S. air power and the determination of the American military to break the siege. Second, the forces he had allowed to be decimated around Khe Sanh could have been employed to far greater advantage in support of the Tet offensive which proved to be an unmitigated disaster for the North Vietnamese forces.

Unfortunately for the United States, the dual victories of Khe Sanh and the suppression of the Tet offensive were totally misinterpreted by the invidious spin placed on them by the media. Khe Sanh had been represented for weeks as being certain to result in a Dien Bien Phu-style defeat for American forces; when the victory was won, accounts of the battle were dropped from the headlines and the editorial pages. At the same time, the Tet offensive, which had cost an estimated 60,000 North Vietnamese casualties–three-quarters of the force–and totally disrupted the enemy military position in South Vietnam, was broadly construed by the media as an overwhelming defeat for the U.S. The media, quite literally, snatched defeat from the jaws of victory.

Ironically, the North Vietnamese were well aware that they had been defeated, and changed their tactics to adapt to their losses. Despite the ambiguities of the time, one fact now stands out. The coordinated use of American air power, augmented by new techniques in the delivery of both cargo and bombs, had decisively shattered the besieging enemy forces at Khe Sanh.

French: Debacle at Dien Bien Phu

The French attempt to re-establish their colonial empire in what had
been French Indochina after World War II had resulted in a losing struggle with the Viet Minh, the Vietnamese Communist forces. In 1953, the French attempted to cut enemy supply lines by occupying Dien Bien Phu, a mountainous outpost on the Vietnamese border near Laos. The Viet Minh quickly cut off all road access, but the French were confident that they could muster enough supplies by air-lift to withstand a siege.

During the winter of 1953, General Giap demonstrated his mastery of logistics by surrounding Dien Bien Phu with 49,000 combatants and more than 30,000 support troops. Armies of men and women toiled to bring in 250 pieces of artillery, which were placed in the high ground around the French forces. The artillery would prove to be decisive for it destroyed the French airstrip early in the battle. Re-supply efforts subsequently depended upon air-drops which became less and less useful as Viet Minh anti-aircraft fire increased and the area held by the French was progressively reduced.

The French were not challenged in the air, but their forces were inadequate to interdict the enemy or to supply their own troops. They had a theoretical maximum of 107 strike aircraft, all of World War II vintage and including Grumman F-6Fs and F-8Fs, Vought F-4Us, Curtiss SB-2Cs, Douglas B-26s and Consolidated PBY4-2s. Their transport force depended primarily on 100 Douglas C-47s and twenty Fairchild C-119s. (The Boxcars were also used as bombers, dropping napalm.) In addition, a mixed bag of civilian aircraft that include Bristol Freighters, a Boeing 307B Stratoliner, the Sud Ouest Bretagne, Curtiss C-46s and Douglas DC-4s operated in support of the besieged forces.

The Viet Minh launched a full scale attack on March 13, 1953. The French held out until May 7th, when the last fortified area was overrun. The battle cost the French 2,200 killed and 6,500 taken prisoners; The Viet Minh had 8,000 killed and 15,000 wounded. It was a price they were willing to pay, for the victory spelled the end of French resistance.

4 responses to “Air Power On Trial: The Siege of Khe Sanh

  1. Walt, 834th was an air division, not a wing. Other than that, it’s a good article.

  2. By the way, come to Warner Robins October 17-21 and meet some of the Khe Sanh airlift veterans.

Leave a Reply