Chapter VIII: 
Fire Support Base CROOK
(June 1969)

Fire Support Surveillance Base FLOYD
(August 1970)
A major innovation of the Vietnam War was the fire support base. Because there were no well-defined battle lines, fire support of maneuver units could not always be accomplished from secure, behind the line positions or from major base areas. Often, positions had to be secured in enemy-dominated territory.
By late 1966 the usual procedure was to establish fire support bases containing headquarters elements, medical facilities, and other support activities, as well as supporting light, medium, and sometimes heavy artillery. Setting up such bases became the routine opening phase of search operations. For example, the beginning of Operation JUNCTION CITY, 22 February-14 May 1967, included a drive by the 1st Infantry Division to open a road northward through War Zone C for the purpose of establishing fire support bases from which the maneuver battalions would operate and receive their artillery support.
These early bases were often attacked by North Vietnamese Army and Viet Cong forces, as they made ideal targets for enemy offensive actions. Eventually, because of the enemy's inclination to attack such installations, fire support bases were established for the express purpose of decoying the enemy. In these instances, sophisticated target detection means including radar, sensor devices, and infrared night sighting devices were used to give warning of the enemy's approach. This combination proved to be eminently successful, and large numbers of attacking enemy forces were destroyed in several such battles at little cost in friendly casualties. The decoy concept was further expanded to include the deployment of fire support bases to facilitate screening of suspected major enemy avenues of approach. This technique was employed extensively by the 25th Infantry Division during the later stages of its tenure in Vietnam.

PICTURE: Fire Support Base Crook, June 1969
June 1969.
The action of 5-8 June 1969 at Fire Support Base CROOK in Tay Ninh province was a classic example of "offensive fire support base" techniques. Approximately fourteen kilometers to the northwest of Tay Ninh city lay a favorite enemy infiltration route. Close to the Cambodian border, the area was a major artery for enemy troops and supplies moving back and forth between War Zone C in the east and Cambodia in the west. In April 1969, Fire Support Base CROOK was established to prevent enemy movement along this route and to provide support for offensive operations in the vicinity. The plan assumed that the enemy would not be able to resist an attempt to knock out the isolated post.
Terrain surrounding the fire support base was flat and generally forested. To the east lay the triple-canopy jungle of War Zone C; to the southwest and west were abandoned rice paddies, while north of the base was scattered double-canopy jungle. Although observation and fields of fire were limited to 200 meters on the east, they ranged out to as much as 1,000 meters over the abandoned rice paddies.

Positioned inside the base was a small force of the 25th Infantry Division, consisting of Company B, 3d Battalion, 22d Infantry; Battery A, 7th Battalion, 11th Artillery, with six 105-mm. howitzers; and elements of the mortar, communications, and medical platoons of the 3d Battalion, 22d Infantry. U.S. planners hoped that the enemy would see Fire Support Base CROOK as an attractive prospect for one of their carefully planned night attacks. Though physically isolated, the base was far from alone. Supporting fire from artillery at other locations as well as from gunships and tactical air elements was arranged around the fire support base perimeter. Early warning was provided for by all available means, including the latest equipment such as sensors, radars, starlight scopes, and patrolling helicopters mounting xenon searchlights.
Preparation of the area surrounding Fire Support Base CROOK was extensive. Bulldozers cleared fields of fire, but isolated patches of concealment were deliberately left to attract North Vietnamese Army reconnaissance parties and observers. These patches were placed so that radar was able to cover them exactly, and direct 105-mm. howitzer fire was ready to destroy anyone using them. There were concentric circles, resembling race tracks, cut at 100-150 meters and 300 meters beyond the fighting positions. These circles were to deny the enemy's rocket propelled grenade gunners ideal firing positions and to increase the effectiveness of U.S. supporting fire. From the air, observers used the circles as a range scale, reducing the chance of error and providing common frames of reference between the observers and the defenders.
The situation at Fire Support Base CROOK remained relatively quiet until the evening of June 5, when the seismic sensors picked up heavy enemy activity less than one kilometer to the northwest. In addition, radar detected small groups moving in the wood lines around the base. Artillery was fired at these areas and, as apprehension of an impending attack grew, the officer in command, Major Joseph E. Hacia, executive officer of the 3d Battalion, 22d Infantry, ordered interdicting fire from supporting artillery on trails, road junctions, and likely assembly areas. Despite the artillery fire, enemy activity continued, and by midevening, Major Hacia had ordered a 100percent alert. At 0255 hours, a barrage by 107-mm. and 122-mm. rockets, 75-mm. recoilless rifles, rocket propelled grenades, and 60mm. and 82-mm. mortar fire was directed at the base. Fortunately, most of the rocket fire went over the base, but mortar rounds hit in and around the perimeter, killing one U.S. soldier. Otherwise, damage was slight.
Co-ordinated with the attack by fire, the enemy launched a battalion-size ground attack from the south and west, which was met by a heavy volume of grazing fire from the defenders. The artillery battery

within the base went into action with a close fire support technique referred to as "killer junior." This technique provided light artillery fire to a depth of 150 to 200 meters around the base, while medium and heavy supporting artillery hit suspected enemy positions throughout the area. On the perimeter, a sixteen-man enemy force did succeed in breaking through the wire with bangalore torpedoes, but it was stopped by riflemen in the bunkers.
By 0400 hours, the full gamut of air support, including tactical air fighters and gunships of all kinds, went into action over the battle area, hitting suspected enemy, rocket and mortar positions and covering all the open areas around the base with fire. Some fifteen enemy. 51-caliber antiaircraft machine guns were reported in action, but they were suppressed by the gunships.
Wilting under the heavy supporting fire, the enemy withdrew into the jungle, and by 0530 the base was receiving only light, sporadic fire. Tactical air and artillery fire continued to pound away at the withdrawing enemy, in an effort to restrict his movement and inflict additional casualties. At first light, B Company moved out of the base on a sweep which uncovered seventy-six enemy bodies and fifteen small arms, plus a variety of ammunition, documents, and extraneous gear.
The next evening enemy activity resumed in almost the same pattern. First, the seismic sensor equipment and radars picked up heavy movement, this time to the northwest and east of the base; then radars began detecting three- to five-man groups moving in the wood lines. All return fire was made with artillery and mortars, including the base's artillery battery, which engaged in direct fire. Although all detectable movement had ceased by 0100 hours, the artillery continued firing "killer junior."
At 0200 hours, a Nighthawk helicopter with a xenon searchlight spotted large groups of enemy troops moving toward the base along the road from the east. Shortly after the artillery shifted and began pounding these new targets, the base was hit with intense enemy preparatory fire followed by simultaneous ground attacks by battalion size forces from the northeast and northwest. Again the base suffered minimal damage, and only three men were wounded.
Army and Air Force gunships, including the Nighthawk helicopter and AC-119 and AC-47 fixed-wing aircraft, engaged the attacking enemy forces under illumination to the northeast and northwest. Additional helicopter gunships suppressed the enemy's .51-caliber antiaircraft guns firing from the west. Available artillery and mortar fire engaged the enemy's supporting positions to the east and south. All this firing, along with intense small arms, automatic weapons, and direct artillery fire from the base itself, wreaked havoc with the attacking enemy battalions.

Despite the volume of defensive fire, the northwestern attacking battalion succeeded in breaching the outer wire before it was stopped. However, the northeastern assault was stopped short of the wire. Most of the attacking force were trapped and cut down in the open as they attempted to withdraw, and by 0530 enemy troops that were able to do so had retreated into the jungle. A sweep of the area on the morning of the third day, 7 June, yielded 323 enemy bodies, 10 prisoners, and over 40 weapons, including two machine guns and two mortars, plus a large quantity of documents, ammunition, and equipment. The following evening the base received light small arms and mortar fire, which caused no casualties. There was no ground attack. In general, this last attack seemed little more than a parting gesture from the badly beaten 272d Viet Cong Regiment.

A total disaster for the enemy, Fire Support Base CROOK was another example of the ability to defeat the North Vietnamese Army and Viet Cong during one of their classic offensive operations. The battle demonstrated the rapid building of a fire base, the use of modern detection equipment, and the integration of the full spectrum of modern fire support techniques to achieve a decisive victory.

Later in the Vietnam conflict, another generation of fire support bases was developed. Fire Support Surveillance Base FLOYD was conceived by the 173d Airborne Brigade as a total interdiction base covering an entire valley floor. The base properly integrated sensors, radar, and other target acquisition means with the system of direct and indirect fire support. Fire base facilities were organized to enable rapid reaction to confirmed targets and to provide adequate base defense. (Diagram 2) The nerve center of the base was the tactical operations center, in which radar and optical scopes and monitoring devices were located. Installing the target acquisition means nearby insured rapid comparison of readouts and confirmation of targets. The mortar fire direction centers were also located in the tactical operations center in order to disseminate target information more efficiently to the indirect fire weapons.

Successful implementation of this fire base concept took place shortly before daylight on 29 August 1970. The 3d Battalion, 2d North Vietnamese Army Regiment, entered a valley in northern Binh Dinh Province from the south and marched openly along the road toward the area of Hoai An District, where they were to occupy mountain base camps and conduct operations against district forces while replenishing their supply of rice. As the enemy column entered the valley, the southernmost sensor was activated, continuing for twenty minutes. A sweep by the PPS-5 radar confirmed that an enemy column was moving north in the valley. The decision was made to engage the rear of the column in the hope of getting a second try at its head. The rear was hit with mortar fire and, as hoped, the

Diagram 2. Fire Support Surveillance Base FLOYD layout, 29 August 1970.
Diagram 2. Fire Support Surveillance Base FLOYD layout, 29 August 1970.

remainder of the column marched on. The radar continued to track the enemy, and additional sensors became active. By this time night observation devices had picked up enemy activity. When the head of the column activated a sensor, it was hit by fire from 105-mm. howitzers, 4.2-inch mortars, and 81-mm. mortars. After this barrage, the PPS-5 and night observation devices confirmed that the enemy was fleeing to the west. Quad .50-caliber machine gun fire pursued the retreating enemy, and mortar fire blocked his escape to the west. Contact was not lost until the enemy left the killing zone.
At first light, a reaction force from the 173d Airborne Brigade began a sweep of the valley floor. Blood trails leading west into the high ground confirmed the accuracy of the barrages. The enemy had not been able to remove all of his dead and wounded. Reconnaissance forces found six dead enemy soldiers and one wounded, along with one AK-50, one 60-mm. mortar, and numerous pieces of individual equipment that had been discarded. On 3 September a wounded enemy soldier, captured in the mountains near the 506 Valley, confirmed that the toll of dead and wounded had been great.
The exact results of the action will probably never be known; however, because of the damage done, the 3d Battalion, 2d North Vietnamese Army Regiment, avoided significant contact with allied forces for several months. The results were substantial considering there was no close contact between infantry units.
Fire Support Surveillance Base FLOYD represented an economy-of-force measure employing a target acquisition system and immediate fire support in an interdiction mission. The terms "killer junior" and "killer senior" referred to direct fire defensive programs of the field artillery. Both techniques were designed to defend fire bases against enemy ground attack and used mechanical, time-fuzed projectiles set to burst approximately thirty feet off the ground at ranges of 100 to 1000 meters. The name "killer junior" applied to light and medium artillery (105-mm. and 155-mm.), while "killer senior" referred to the same system using eight-inch howitzers. This technique proved more effective in many instances than direct fire with "beehive" ammunition, because the enemy could avoid the beehive ammunition by lying prone or crawling. For example, in October 1967 during the battle of  Xa Cat, which. involved an attack by several enemy battalions on the 1st Infantry Division's Fire Base CAISSON VI, artillery firing beehive ammunition had little effect on attacking enemy troops, because they approached the perimeter by crawling. However, a switch to timefuzed explosives stopped the advance. Another successful application of the "killer" technique was in clearing snipers from around base areas.
In building Fire Support Base CROOK, many of the rapid construction techniques which had been developed during the previous

months, while positioning divisional patrol bases along the Cambodian border, were used. Construction usually started early in the day and proceeded according to the following steps. The exact position of the fire support base was selected and an engineer stake was driven at the center. A rope forty meters long was attached to the stake and stretched out from the center, forming the radius of the base and establishing the location of the bunker line. Next, an aiming circle was positioned at the center and a stake was driven at 0 to mark the location of the first bunker. Additional stakes were driven every 15 around the perimeter to mark the location of all twenty-four bunkers, which had been established as the ideal number for a rifle company. Another circle was marked seventy-five meters out from the bunker line, thus establishing the location of the defensive wire barrier.
After the bunker positions had been marked, a standard package was dropped at each of the twenty-four stakes by a helicopter. This package contained one fifteen-pound, shaped demolition charge; two sheets of pierced steel planking; and a bundle of sandbags. The shaped charges were placed next to the engineer stakes, and the initial hole for the bunker was blown. A standard nine-foot bunker was then built by using the pierced steel planking and sandbags and by squaring up the blown crater.
While the fighting bunkers were being constructed, bulldozers were busily digging holes for larger command and control bunkers inside the perimeter. The beans were pushed up for artillery firing positions and later between the bunkers on the outer perimeter. The wire barrier was established using one row of triple concertina wire. The area between the bunker line and the wire barrier was then laced with claymore mines. The fire support base was completed when a Chinook helicopter flew in with a fully assembled, twenty-foot observation tower. Time of construction varied, but in each case the company defending the base was dug in with complete overhead cover by nightfall of the first day.
The fights at Fire Support Base CROOK and Fire Support Surveillance Base FLOYD demonstrated the successful integration of sensor devices to provide early warning and identification of enemy units. These devices were positioned either through the air or by hand and could detect the movement of humans within a range of about 40 meters and of vehicles within 300 meters.
Other target acquisition devices used successfully at Fire Support Base CROOK and Fire Support Surveillance Base FLOYD were the ground surveillance radars and the night observation devices. The radar sets organic to division maneuver battalions were used primarily to provide short- and medium-range identification and location of enemy targets during periods of limited visibility. The AN/PPS-5 radar had a maximum range of 5 kilometers and the AN/PPS-4 radar

PICTURE: Aerial Delivered Seismic Intrusion Dectector
had a 1.5-kilometer range for personnel detection. Both were used to protect the night defensive positions. Along with radar there were the night observation devices, either the older infrared lights or the newer starlight scopes. These scopes intensified the available light rather than emitting a light source of their own. The new sensors were of limited value in themselves, but when properly integrated into an overall surveillance and target acquisition plan, as at Fire Support Base CROOK and Fire Support Surveillance Base FLOYD, they were most effective.

A final innovation was the artillery ambush, a technique developed by the 1st Battalion, 77th Artillery, 1st Cavalry Division Artillery. The ambush involved the covert planning of a homemade trip flare device with the trip wire running across the road. A fire unit was laid on this grid and fired on the flare signal. Two flares of different colors could be used to determine the direction of travel of the target unit. Later, with the arrival of the modern sensor devices, the technique was further refined.
In conclusion, the unique employment of the fire support bases in Vietnam can be considered an innovation. The use of these bases to

PICTURE:  Starlight Scope, Rifle-Mounted Night Observation Device

invite enemy attacks, the placement of the bases, the techniques of co-ordinating supporting fire, and the co-ordination of target acquisition means were prime examples of the integration of various methods and the use of new equipment to destroy the enemy.

page created 15 December 2001

Previous Chapter     Next Chapter

Return to the Table of Contents