Operation Niagara

By late January 1968, American intelligence sources detected the presence of 20,000 or more North Vietnamese soldiers in the vicinity of Khe Sanh. 1 American tactics were to allow the enemy to surround the 26th Marine Regiment (Reinforced) at Khe Sanh, to mass their forces, to reveal troop formations and logistic routes, to establish storage and assembly areas, and to prepare siege works. The result would be the most spectacular targets of the Vietnam War for American firepower.

General William C. Westmoreland, commander of U.S. forces in Vietnam, chose the code name Operation NIAGARA for the coordination of available firepower at Khe Sanh. According to Westmoreland, the name NIAGARA invoked an appropriate image of cascading shells and bombs.3 NIAGARA would be composed of two elements. NIAGARA I was an comprehensive intelligence-gathering effort to pinpoint the available targets, while NIAGARA II was the coordinated shelling and bombing of these targets with all available air and artillery assets.

The efficacy of the firepower available to the Marines at Khe Sanh was a function of the accuracy of the target selection processes. The intelligence section (S-2) of the 26th Marine Regimental headquarters company was tasked with the responsibility of acquiring targets. S-2 had knowledge of the siege strategy employed by the North Vietnamese Army (NVA) at Dien Bien Phu in 1954 and Con Thien in 1967. These historical lessons were used to predict the behavior of the enemy at Khe Sanh.

Various sources were utilized to develop a view of enemy activity around the Khe Sanh plateau. Sources external to the immediate battlefield included intelligence reports from the Military Assistance Command (MACV) in Saigon, III Marine Amphibious Force (III MAF) headquarters in Da Nang, as well as the headquarters of the 3d Marine Division at Phu Bai.

Intelligence was generated locally via a variety of means. Hundreds of acoustic and seismic sensors were seeded around the combat base. This comprehensive sensor system cost approximately a billion dollars and was credited with reducing the number of Marine deaths sustained during the fighting by fully fifty per cent. 4 By Marine estimates, forty percent of the raw intelligence obtained at Khe Sanh was provided by the sensor system. 5 Ground and aerial observers provided visual evidence of enemy activity, as did photo reconnaissance. Crater analyses from incoming rocket, mortar, and artillery rounds were conducted to determine the likely source of the attacks. Shell/flash reports yielded additional targets. Infrared imagery and analysis of intercepted enemy communications were also used.

Marine reconnaissance patrols, Army Special Forces, Central Intelligence Agency personnel, and the MACV Studies and Observation Group (SOG) all provided input to the 26th Marines S-2. The CIA Joint Technical Advisory Detachment and SOG obtained their information from casual encounters from villagers; from regular paid agents, including Rhade and Bru Montagnards, and from locals who desired being hired as agents of the U.S. intelligence community around Khe Sanh.

Likely or confirmed targets were then attacked by the firepower available to the Marines at Khe Sanh. It was the base Fire Support Coordinating Center (FSCC) that was responsible for coordinating the array of supporting arms.

After making the trip down the Ho Chi Minh Trail through Laos, the North Vietnamese established various forward logistic bases within a few thousand meters of the combat base. During periods of darkness the Communists dug shallow trenches leading from their supply points toward the U.S. positions. American intelligence noticed this trenching system around February 23, 1968. Once the trenching system had been constructed close to the base, secondary trench lines branched off and paralleled the Marine perimeter. These close-in, secondary trenches were constructed for the purpose of launching ground attacks against the base.

Initial FSCC fire tactics were to saturate infiltration routes into the area around the combat base with artillery fire and air strikes. These fires slowed down NVA trenching efforts, but were unable to halt them completely. From a logistic standpoint, it was impossible to deliver sufficient munitions to saturate the trenching systems with massed artillery fire. Consequently, the FSCC altered its tactics. The NVA were permitted to construct their trench systems close to the base in order to simplify pin-pointing and killing them with supporting arms.

The sensor system quickly proved its worth. During the night of February 3-4, the sensor arrays indicated the presence of up to 2,000 North Vietnamese soldiers in the vicinity of Marine hill outposts northwest of the combat base. Defensive artillery fires were ordered against these troop concentrations. Sensor monitors reported hearing men screaming in panic and the sounds of troops fleeing their assembly areas. The NVA units were completely destroyed in their assembly areas and the intended attack was effectively broken up. This incident is one of the earliest examples in warfare of a ground attack entirely thwarted on the basis of remote sensor data.

By crater analysis, it was possible to confirm locations that were suspected based on other intelligence sources; detect the presence and location of enemy batteries; assist in counterbattery fires; and detect the presence of new types of enemy weapons, new calibers, or new munitions. The direction of flight of a projectile can be determined with reasonable accuracy from its crater, ricochet furrow, or, in the case of dud rounds, soil tunnel.

The particular characteristics of the soil at Khe Sanh often yielded valuable information from crater analysis techniques. A stick placed in the clay soil tunnel made by a dud round would point in the direction of origin, and the angle of the stick indicated the angle of fall. By measuring this angle and using the firing tables of enemy weapons types, counterfire personnel were able to compute the range of the enemy weapon. Inspections of shelled areas were made as soon as possible after the shelling.

Staff Sergeant Bossiz Harris, the acting gunnery sergeant of Mortar Battery, 1st Battalion, 13th Marines, was known to conduct crater analyses during incoming fire. This allowed the 1st Battalion, 13th Marine Fire Direction Center (FDC) to direct prompt return fire. Rapid and accurate counterbattery fire could force the enemy artillerymen to seek cover from American incoming, thereby curtailing their fire mission, as well as destroying NVA guns and gun crews.

In order to minimize the reaction time of the Marine and Army artillerymen at Khe Sanh, Colonel Lownds periodically entered the regimental FSCC bunker, indicated a spot on the wall map, and directed the senior artillery officer to hit the marked spot. The coordinates were sent to the FDC, computed, and sent to the appropriate gun crew, who adjusted their tubes. This aiming process usually took less than forty seconds before a round was on its way. During the battle, 1st Battalion, 13th Marine guns fired 158,891 mixed artillery rounds in direct support of the 26th Marines at Khe Sanh.

Acquiring data on enemy troop locations was one thing; giving that data a correct interpretation was quite another. On the first day of the 1968 Tet Offensive, intelligence analysts on the MACV staff received a set of infrared imagery photos. This information was interpreted as indicating NVA troop movements away from the combat base. Analysts examining sensor readout data concluded these troops were closing in on the base in preparation for a massive attack. In actuality, no enemy ground attacks were launched around Khe Sanh during this period.

Shortly after the beginning of the Tet Offensive, aerial reconnaissance and communications intelligence indicated the existence of a major target in the Khe Sanh TAOR. Photo analysts spotted a bank of radio antennas at a limestone cave complex in the DMZ northwest of Khe Sanh. Radio signals emanating from this group of caves showed it to be a major enemy headquarters. There was speculation that North Vietnamese Minister of Defense Vo Nguyen Giap himself was personally supervising the battlefield from this location. Repeated B-52 attacks by the U.S. Seventh Air Force were launched against the cave complex. These actions knocked the enemy radio system off the air temporarily and even managed to seal the cave entrance with rocks and other debris. In spite of these attacks, the cave complex headquarters remained in operation for several weeks.

One Marine spotter on Hill 881 South, Lance Corporal Molimao Niuatoa, was gifted with especially sharp vision. Niuatoa was scanning the landscape with a pair of 20-power naval binoculars when he noted the muzzle flash of a NVA artillery piece firing from a distance of 12,000 to 13,000 meters from his position. The location was noted by the spotter. As this gun position was beyond the range of Marine artillery, it could only be taken out with air strikes. An observation aircraft was directed into the general vicinity. This observer did not know the exact location of the gun and so fired a 2.75-inch smoke rocket in the general vicinity of the target. A Marine A-4 Skyhawk jet dropped a 500-pound bomb on the marking rocket. Niuatoa adjusted by noting the location of the billowing bomb smoke in relation to the artillery piece and called in corrections to the spotter aircraft. More smoke rockets were fired and additional strings of bombs were dropped. These corrections and bracketing continued until a Skyhawk on its fourth pass scored a direct hit on the gun position, yielding a series of secondary explosions.

After 1965, air power in South Vietnam was deployed to extend and compliment the effectiveness of field artillery. Although the 26th Marines possessed thirty artillery pieces as well as tanks and recoilless rifles, the fact that the base could only be supplied by air placed limits on the Marines' ability to saturate the Khe Sanh area with artillery-delivered munitions. It was airpower that would elevate the flood of firepower to Niagara-sized dimensions.

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