Page Title - US Artillery
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Fire Support Bases


The hallmark of ground maneuver which dominated Army tactics in Vietnam was the fire support base, often referred to simply as firebase. Conceptually, the fire support base functioned simply to provide a secure but mobile artillery position capable of rendering fire support to infantry operating in areas beyond the normal range of their main base camp cannon and howitzers. A typical FSB could be expected to deploy 6 x M102 105mm field howitzers and anything from a company to a battalion of infantry with it's supporting 81mm mortars, communications, medical and administrative personnel

This concept afforded infantry a greater degree of flexibility without sacrificing artillery protection. However, firebases quickly became targets for enemy counterattacks and bombardments, and increased defensive measures were undertaken. More sophistication meant less mobility. Over the course of the war, firebases developed to the point where ground maneuver was hampered because of their size, elaborate construction, demand on supply and protective resources, and troop reluctance to leave their comforts and safety, a condition called "firebase psychosis."

The 1st Cavalry Division (Airmobile), as the most tactically mobile formation in Vietnam, gave priority to rapid firebase deployment and construction. In order adequately to cover its large areas of operations, the division was constantly opening, closing, and reopening firebases throughout the war. The first division firebase was designated as Bill, built during October 1965 in Pleiku Province. However, by 1969 they had blossomed from jungle clearings with unsophisticated defenses into formidable semi-permanent fortresses.

The typical cavalry fire support base was a defensive area roughly 250 yards in diameter with an 800-yard perimeter, which contained howitzers and enough equipment and supplies to support the infantry with artillery fire around the clock. The firebase also supplied logistics, communications, medical, and rest facilities for the cavalrymen within its area. The division's 8th Engineer Battalion was responsible for initiating firebase construction. The engineer line companies, assigned one to a brigade, cleared the initial area, performed demolitions work, established water points, and provided the supervisory expertise, equipment, and manpower to build sophisticated fieldworks.

Typical artillery fire base

Once the fire support base site was selected, usually by aerial photographic reconnaissance at division level, the brigade and battalion responsible for its sector began detailed construction planning. Terrain and weather information were used to determine its size, shape, and required facilities. Construction priorities were then issued, hopefully in a timely fashion. It was proven repeatedly that minutes spent in coordinated planning by all concerned units saved hours in actual construction time. The normal order of construction was: temporary helicopter pad for delivery of supplies, howitzer positions, perimeter berm, artillery fire direction center (FDC), infantry tactical operations center (TOC, the command post), ammunition supply point, "VIP" helicopter pad, garbage sump, defensive wire barrier, and, finally, medium artillery positions if applicable.

The division prepared basic firebase kits, each designed for a battalion-level fire support base and its supporting six light howitzers, which contained all the necessary materials for construction. Nails, spikes, metal culverts, chain-link fence rolls, tar paper, sandbags, pickets, and lumber were all pre-palletized or arranged in sling-loads for rapid helicopter delivery. The firebase kit required about twenty-five CH47 Chinook cargo helicopter sorties to deliver to the field.

The amount of equipment needed to clear the area of the firebase varied depending upon terrain. In dense jungle large Air Force bombs were used to demolish enough vegetation to blast out a landing zone. The more common bomb of this type was the 750-pound "Daisy Cutter" that detonated about ten feet above the ground, effectively destroying all foliage for ten feet around and knocking down trees over a considerably larger radius. The 10,000-pound "Instant LZ" opened up larger swaths of demolished jungle, while late-war 15,000-pound "Commando Vault' bombs offered the most destructive power. Napalm was a useful supplement if tropical forests were clogged with bamboo or additional thick jungle growth.

The air assault to secure and establish the firebase site was the riskiest part of the construction task. If the site was not large enough to accommodate the landing of a single helicopter, combat engineers with axes and explosives rappelled from a helicopter hovering fifty to one hundred feet above the ground. They were escorted by small parties of volunteer infantry which provided security while the engineers cleared an area large enough for the CH-47 Chinook and CH-54 Flying Crane cargo helicopters. Using demolitions and chain saws, the assault engineers could clear a landing zone for the larger helicopters within three hours. Of course, in most instances the selection of open fields demanded only a small amount of advance clearing.

The foremost task of any firebase construction effort was to produce a tenable tactical position by nightfall on the first day, with overhead cover for every man. This "tactical phase" was a time of heavy helicopter traffic bringing in more engineers and their equipment, the infantry and artillerymen, ammunition, barrier and bunker materials, rations, fuel, water, and howitzers and other weapons. As soon as the perimeter trace was cut out, defensive positions were started.

The normal construction site required the use of one engineer platoon under the direction of a "project engineer" with two medium D6B dozers, two Case light dozers, and one backhoe. As engineers worked with explosive charges, bangalore torpedoes, and chain saws to expand the perimeter, the first vehicular machines were being flown to the area. The invaluable light dozers could be airlifted in one piece underneath Chinooks and were the first equipment in. They were used to clear fields of small trees and stumps and to level artillery positions. The backhoe dug emplacements for the TOC, FDC, medical bunker, and perimeter bunker. Heavy dozers were lifted in two pieces, the blades and tracks by Chinook and the tractor body by Flying Crane. Once hauled in, the dozer had to be assembled, which required at least thirty minutes (more if the pilot did not set the machine down on its tracks); then it was immediately put to work pushing up earth to create a four-foot berm completely around the perimeter.

As engineer dozers and backhoes carved out the main firebase defenses, the infantry and artillerymen began emplacing wire entanglements, digging perimeter fighting holes, and emplacing perimeter bunkers in backhoe excavations. "Quick Fix" combat bunkers were simply five-foot-by-eight-foot shoulder-high holes covered with lumber or natural timber and sandbags. Standard perimeter bunkers provided better protection because they were covered by wooden stringers and steel mat decking. The simplest fighting positions were the two-man foxholes, each covered by three sections of sixty-inch metal culverts and topped by sandbags. In the meantime, once the first strand of tactical wire was emplaced, the artillerymen returned to build ammo storage bunkers and parapets around their weapons.

The final defensive phase of construction began when the Chinooks had delivered enough kit material to permit the engineers to build the main infantry TOC, artillery FDC, and medical bunker. These were built using large dimensional timbers, precut to anticipated firebase requirements. The main bunkers were started at the end of the first day or the beginning of the second day and finished by the end of the fourth day. Construction time was often shortened by employing reusable TOC and FDC bunker modules. Bunker modules were composed of two CONEX containers emplaced facing each other, with the overhead gap between them covered by steel matting. Two modules (four containers) sufficed for a battalion command center. Using these containers allowed an operational TOC/FDC complex to be completed within eight hours, including pushing earth fill around the sides and sandbagging the tops.

The infantry and artillerymen continued improving the wire barriers with tangle-foot and a second perimeter strand. Individual sleeping positions were built using metal seventy-two-inch half-culvert sections. The improvement of firebases was a never-ending job, as all structures were continually reinforced, surface drainage improved, and fields-of-fire constantly maintained by additional clearance. One squad of engineers was normally kept on any fire support base.

The life span of a fire support base depended on the tactical situation in its area. Since firebases were normally established to give a battalion and its direct support howitzer battery a pivot of operations to patrol the immediate vicinity, the firebase was closed when the battalion relocated. When the decision was made to close out a firebase, the brigade engineer usually provided one platoon to assist the infantry company tasked with dismantling it. Structural removal was aimed at salvaging the timbers, culverts, steel matting, and chain-link fencing in order to reconstitute division firebase kits, but holes were filled and berms leveled at command discretion.

The 1st Cavalry Division's fire support bases were another example of adopting traditional frontier cavalry forts to the Vietnam environment, fusing airmobility to enhance the process. The advent of helicopter support and better material resources allowed these forts to be established more quickly and more often and projected cavalry battalions into hostile territory with greater assured safety. Once emplaced, however, they effectively limited cavalry movement to the radius of their guns. More substantial firebases of a semi-permanent nature mushroomed into major camps with recreation areas, snack shops, mess halls, and elaborate living facilities, which actively hindered field operations because of their large garrison requirements.

Construction and Layout

There was a standard drill for the construction of a FSB.

  • Following recon and site selection, a stake was positioned at the center of the chosen site and a 131' (40m) rope was used to mark the bunker line
  • The bunker line was marked by stakes at 15' intervals to indicate the individual infantry bunker positions
  • A circle of 246' (75m) radius marked the line of the perimeter wire
  • At each bunker position, helicopters dropped a standard pack of 1 shaped demo charge, 2 sheets of pierced steel planking and empty sandbags which were used to construct a 9' (2.7m) bunker
  • Bulldozers excavated ground for the CP and the FSCC or FDC and pits for the guns and mortars
  • A prefabricated 20' (6m) observation tower was flown in by CH-47
  • Time taken for construction varied but it was deemed essential that the outer defences and infantry positions were completed by last light on the first day of the occupation of the FSB site

Schematic diagram of fire support base layout


  1. FSCC - Fire Support Co-ordination Center
  2. Communications Center
  3. Administration & Stores
  4. 105mm Gun Pits
  5. 81mm Mortar Pits
  6. Observation Tower
  7. Command Post
  8. Ground Surveillance & Anti-personnel radar emplacements
  9. Night observation devices, searchlights for visible/infra-red illumination
  10. Perimeter - triple dannart barbed wire, claymores, trip flares & Fougass
  11. Infantry Bunkers


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