Operation
NIAGARA
©1998
Peter Brush
Note: An edited version of this article appeared
on Vietnam magazine’s website, The History Net (www.thehistorynet.com)
in December, 1999.
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.2
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.6
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.7
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.8
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.9
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.
Khe Sanh had top-priority claim on all U.S.
air assets in Southeast Asia. B-52s, personally directed by General Westmoreland
from the Saigon MACV combat operations center, came from Guam, Thailand, and
Okinawa. The Marines and U.S. Air Force provided fighter-bomber support from
bases within South Vietnam. Naval aviators from Task Force 77 flew sorties from
aircraft carriers in the South China Sea. The South Vietnamese Air Force and
U.S. Army aviation also provided aerial support. From B-52s, originally
designed as high-altitude strategic bombers for the delivery of nuclear
weapons, to propeller-driven A-1 Skyraiders, the entire spectrum of American
fixed-wing and rotary aircraft were deployed to support the 26th Marine
Regiment at Khe Sanh.
Air representatives worked with their
artillery counterparts in the Fire Support Coordination Center. Requests for
air support were channeled through the Tactical Air Direction Center of the 1st
Marine Air Wing (1st MAW) at Da Nang. If the 1st MAW could not fill a quota,
liaison teams from other services were called upon for their support. The
priority for air support was so high that at times the sky over Khe Sanh
resembled "a giant beehive."10 Upon arrival, aircraft were
normally directed into a holding pattern until a ground controller or ground
radar operator was free to direct the strike. Often these patterns extended
upward to 35,000 feet with dozens of aircraft gradually corkscrewing their way
downward as each flight delivered its ordnance and departed Khe Sanh airspace.
A pilot might be directed to a succession of holding points only to end up with
his fuel expended and his full load of ordnance still on board. If the pilot
ran out of fuel before his turn came to deliver a strike, he was forced to
jettison his bombs and return to base.
The contribution of U.S. Navy aviation
reflected events in North Vietnam. Clouds that enveloped North Vietnam airspace
forced a reduction in the number of Navy sorties there and the released planes
and munitions were re-directed against targets around Khe Sanh. In February,
about seventy-seven percent of Navy carrier sorties planned against North
Vietnam were altered in this manner. One naval aviator who attacked the NVA
trench system described the detonation of his 1,000-pound delayed action bomb
as resembling the eruption of volcanoes. After collapsing fifty meters of
trench, the NVA abandoned the building of assault positions in this area.11
Close air support was employed against
pinpoint targets in proximity of friendly troops. Usually there were
fighter-bombers overhead at Khe Sanh around the clock. Tactical air controllers
in light airplanes or helicopters maintained communications between strike
pilots and troops on the ground. The tactical controller made a marking run by
firing a smoke rocket or throwing a colored smoke grenade at the target to be
attacked. When the strike pilot saw the smoke, dummy passes were made until the
controller was satisfied the jets were lined up on the proper target. Bombing
runs were executed and short corrections were made via radio until all ordnance
was expended. The tactical air controller would then fly over the target to
record the effectiveness of the strike. Battle Damage Assessments were relayed
to the departing aircraft for intelligence debriefings upon return to base.
Ground-controlled radar bombing was employed
in periods when the target could not be acquired due to bad weather. Radar
controllers operated from a heavily reinforced bunker which contained fragile
computer equipment and the TPQ-10 radar used to guide aircraft to their target.
This radar emitted a beam which locked onto the aircraft. Using targeting data
acquired from the FSCC, the controller programmed the computer with information
on enemy position, ballistic characteristics of the ordnance, wind speed and
direction, and other relevant data. At a predetermined release point, the
controller instructed the pilot when to release his bombs. In
specially-equipped aircraft such as the twin-engine Marine A-6 Intruder, the
bombs could be released automatically by the ground controller. Marine
controllers routinely directed strikes as close as 500 meters from friendly
positions. The Air Force liaison officer felt strikes could be conducted to
within fifty meters in case of emergency.12 Marine air flew 7,078
sorties and delivered 17,015 tons of ordnance in defense of Khe Sanh, while the
U.S. Air Force tactical aircraft contributed 9,691 sorties and 14,223 tons of
munitions.13
The most spectacular display of aerial power
at Khe Sanh was provided by the B-52 Stratofortresses. With a payload of 108
500-pound bombs per plane, these Arc Light strikes were conducted against area
targets such as troop concentrations, supply areas, and bunker complexes. These
targets were programmed into on-board computers and were launched from
altitudes above 30,000 feet. Arc Light bombing procedures were based on a grid
system, with each block in the NIAGARA area represented by a one by two
kilometer box superimposed on a map. Three B-52s, composing one cell, could
effectively blanket such a box with high explosives. On average, every ninety
minutes one three-plane cell of B-52s would arrive on location around Khe Sanh
and be directed to a particular target by a controller. Several flights of
B-52s could churn up boxes of terrain several thousand meters long. Many enemy
casualties were sustained from concussion alone. In some instances, NVA
soldiers were found after an Arc Light strike wandering around in a daze with
blood streaming from their noses and mouths. To catch these stunned survivors
above ground, artillerymen at Khe Sanh often placed massed artillery fire into
the Arc Light target area ten to fifteen minutes after the departure of the
heavy bombers.
Arc Light attacks delivered a total of
59,542 tons of munitions from 2,548 sorties during the siege.14
General Westmoreland was elated at the performance of B-52s, going so far as to
maintain that the battle of Khe Sanh was won by the officers and men of the 3d
Air Division (B-52). According to Westmoreland, the thing that broke the backs
of the NVA at Khe Sanh was "basically the fire of the B-52's."15
This high praise notwithstanding, Arc Light
attacks had some limitations. A North Vietnamese soldier captured in April
1968, told his interrogators that his unit received frequent, timely, and
accurate warnings of impending B-52 attacks. These alerts came either by radio
or telephone and usually provided two hours' notice, sufficient for the NVA to
depart the planned strike area. The NVA prisoner was not certain as to the
origin of these warnings. Possibilities include Soviet intelligence-gathering
trawlers operating in the Pacific and the interception of communications sent
to or from the MACV combat operations center at Tan Son Nhut air base near
Saigon.16
The Target Intelligence Officer at Khe Sanh,
Captain Mizra M. Baig, felt that Arc Lights were an accurate weapon which could
be employed around Khe Sanh much the same as other supporting arms. However,
since requests for B-52 strikes were submitted fifteen hours prior to the drop,
Arc Lights could never be as responsive or flexible as tactical air and
artillery. Techniques were developed by the FSCC to combine and compliment the
strengths of aerial and artillery support. One such technique was the Mini-Arc
Light.
When intelligence data indicated the
presence of NVA units in a certain region, the FSCC computed a 500 by 1,000
meter box in the center of the suspected assembly area or likely route of
movement. Two A-6 Intruders, each armed with twenty-eight 500-pound bombs, were
placed on station. Army 175mm guns at the nearby artillery bases at Camp
Carroll and the Rockpile initiated the Mini-Arc Light by pouring sixty
150-pound rounds into one half of the block. Thirty seconds later the A-6s
unloaded their ordnance in the middle of the block. At the same time, the
artillery at Khe Sanh poured an additional two hundred artillery and mortar rounds
into the target area. Fire coordination was such that bombs and artillery
shells hit at the same instant. When properly saturated with munitions, enemy
soldiers caught in the zone "simply ceased to exist."17
The Mini-Arc Light could be put into effect
in about 45 minutes. To reduce reaction time even further, a Micro-Arc Light
was executed. The block size was reduced to 500 by 500 meters. Any aircraft on
station could be used for bombing. The Micro could be planned and executed
within ten minutes. Twelve to sixteen 500-pound bombs, thirty 175mm artillery
rounds, and 100 mixed lighter artillery rounds from Khe Sanh batteries could be
unloaded on the target block within ten minutes. On an average night, three to
four Minis and six to eight Micros were executed in the vicinity of the Khe
Sanh Combat Base.18
Because the Marines at Khe Sanh were
surrounded by North Vietnamese, the base could neither be supplied nor
evacuated by ground operations. Consequently, an effective method of aerial
resupply was vital to the continued existence of the base. The principal source
for supplies destined for Khe Sanh was Da Nang, a thirty minute flight. C-130s
and C-123s provided the bulk of the supplies. Transport crews used speed
offloading techniques to minimize the time they spent on the ground at Khe
Sanh. When weather or hostile fire prevented transport aircraft from actually
landing at the airstrip, parachute and various cargo extraction systems were
employed to permit the unloading of cargo without putting the planes' wheels on
the ground.
The Marine hill outposts, originally
supplied from the base at Khe Sanh at the beginning of the siege, were
thereafter served by externally-loaded helicopters flying from the Marine base
at Dong Ha. Air Force and Marine crews en route to Khe Sanh flew the last few
miles through a wall of enemy anti-aircraft fire - maintenance men at Da Nang
noted 242 holes in one C-130 before they gave up counting.19
As tactical air supported the Marines on the
ground, so too did it accompany transport aircraft on their supply missions
into the Khe Sanh TAOR. North Vietnamese antiaircraft guns in calibers up to
37mm were dug into the hills around Khe Sanh and menaced the existence of the
aerial highway leading to the base. By March, the danger from enemy fire was so
acute that all transports were provided with tactical air escorts. Air planners
drew on their maps a line indicating the flight path of a cargo plane from the
time it dropped below 3,500 feet above ground until it regained that altitude after
disgorging its cargo. The potential danger area from which a 37mm gun could hit
a plane was calculated. Fighter bombers were directed against known or
potential enemy gun positions using 20mm cannon and fragmentation bombs. These
attack runs commenced when the cargo planes reached an elevation of 1,500 feet
above the ground.
In clear weather, two fighters laid down
smoke screens for concealment on both sides of the flight path of the incoming
transports. During the siege, every 37mm gun emplacement was repeatedly
attacked until intelligence showed the gun to be destroyed or abandoned. More
than 300 antiaircraft sites were reportedly destroyed.20 When
considered necessary, Air Force F-4 Phantoms equipped with cannon were kept in
the area to provide combat air patrols to disincline the North Vietnamese Air
Force from intervening in the fighting around Khe Sanh. Carrier-based aircraft
bombed airfields in North Vietnam that short range enemy MiGs would have had to
use to attack the Marine positions.
General Westmoreland was certain the North
Vietnamese intended to overrun the Marine base at Khe Sanh as they had done at
Dien Bien Phu. If so, air power was instrumental in denying victory to the
Communist forces. Weather and other considerations prevented accurate
measurement of the damage sustained by enemy forces from Operation NIAGARA.
Photo reconnaissance and direct visual observation credited NIAGARA forces with
causing 4,705 secondary explosions, 1,288 enemy killed, 1,061 structures
destroyed, 158 damaged, 891 bunkers destroyed, 99 damaged, 253 trucks
destroyed, and 52 damaged. Enemy personnel losses were estimates; they could
not be confirmed since an actual body count was not possible. Westmoreland's
Systems Analysis Office produced four models from which its analysts concluded
that total NVA casualties - killed and wounded seriously enough to require
evacuation - numbered between 9,800 and 13,000 men. The generally cited figure
of 10,000 casualties represents half the number of NVA believed committed to attacking
the Khe Sanh Combat Base at the beginning of the fighting there. 10,000
casualties represents fifty-nine percent of the number of enemy killed in all
of I Corps during the 1968 Tet Offensive.21
The one billion dollars worth of aerial
munitions expended by the U.S. during the siege totaled almost 100,000 tons.
That amount equaled almost 1,300 tons of bombs dropped daily, and represents an
expenditure of five tons for every one of the 20,000 NVA soldiers initially
estimated to be committed to the fighting at Khe Sanh.22 This
expenditure of aerial munitions dwarfs the amount of munitions delivered by
artillery, which totals eight shells per enemy soldier believed to have been on
the battlefield.
General Giap claimed Khe Sanh was never of particular importance to the North Vietnamese. According to Giap, it was the U.S. that made Khe Sanh important because the Americans had placed their prestige at stake there.23 In the larger scheme of things, the fighting at Khe Sanh was of little lasting significance. Before the bombs and shells of Operation NIAGARA stopped falling on the Khe Sanh battlefield, U. S. President Johnson ordered severe restrictions on aerial and naval attacks against North Vietnam, declared the readiness of the U.S. to begin peace discussions to end the war, and declined to seek reelection to the presidency. In June 1968, the base at Khe Sanh was abandoned by the Americans. Ultimately, the U.S. would learn that it was unable to win at the conference table what it could not win on the battlefield.
1 Robert L. Pisor, The End of the Line (N.Y.: Ballantine Books,
1982), p. 9.
2 Pisor, p. 86.
3 William C. Westmoreland, A Soldier Reports (Garden City,
N.Y.: Doubleday, 1976), p. 339. Strictly speaking, Operation NIAGARA referred
specifically to the use of aerial firepower at Khe Sanh. However, since there
was a high degree of coordination between aerial and artillery firepower, and
in keeping with Westmoreland's image of cascading shells and bombs, this
article includes descriptions of all firepower deployed by the U.S. in support
of Khe Sanh during the siege.
4 John Prados and Ray W. Stubbe, Valley of Decision (Boston,
MA: Houghton Mifflin, 1991), p. 303.
5 Bernard C. Nalty, Air Power and the Fight for Khe Sanh
(Washington, D.C.: Office of Air Force History, U.S. Air Force, 1973), p. 95.
6 Prados, p. 304.
7 Moyers S. Shore II, The Battle for Khe Sanh (Washington,
D.C.: Headquarters, U.S. Marine Corps, 1969), pp. 107-109.
8 Peter MacDonald, Giap: The Victor in Vietnam (N.Y.: Norton,
1993), p. 282; Phillip B. Davidson, Vietnam at War (Novato, CA: Presidio
Press, 1988), p. 563.
9 Shore, pp. 97-98.
10 Shore, p. 95.
11 Nalty, pp. 61-62.
12 Shore, pp. 103-104; Nalty, pp. 66-67.
13 Prados, p. 297.
14 Prados, p. 297.
15 Quoted in Nalty, p. 88.
16 Nalty, p. 88.
17 Shore, p. 110.
18 Shore, 110-111.
19 Prados, p. 374.
20 Nalty, pp. 63-64.
21 Nalty, 103-105.
22 William Head and Lawrence E. Grinter (eds.), Looking Back on
the Vietnam War (Westport, CT: Praeger, 1993), p. 173; Prados, p.
297.
23 Oriana Fallaci, Interview With History, (New York, N.Y.:
Liveright, 1976), pp. 85-86.