Service Info
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Gunners of C Battery, 1st Battalion, 13th Marines, attached to Special Landing Force Bravo, fire their 105mm howitzer into enemy positions from Fire Support Base (FSB) Rattlesnake in support of Operation Oklahoma Hills. (National Archives)

Dangerous Rings Of Fire

With no front lines on the Vietnam battlefields, American commanders found the positioning of artillery to be a serious problem. The fire support base, which allowed artillery forces to move where needed, was the solution.

By Michael R. Conroy

From the catapults of the Roman legions to the siege guns of the Middle Ages to the massed artillery of the Korean War, where the U.S. X Corps alone fired more than 27 Liberty shiploads of artillery ammunition to stop the 1951 Chinese offensive with a wall of steel, artillery has always played a major role on the battlefield. And Vietnam was no exception.

Indeed, artillery marked the climax of the First Indochina War between the Viet Minh and the French. During the Battle of Dien Bien Phu, General Vo Nguyen Giap's artillery fired more than 100,000 rounds of 75mm or greater, pounding the French defenders into submission. Artillery would also have a major part in U.S. operations during the Second Indochina War, but first it had to adapt itself to battlefield peculiarities.

A Rapid Solution

Unlike past wars where there was a fixed front line, the Vietnam battlefield was fluid and nonlinear. This meant that it was no longer possible to support combat operations from fixed positions in the rear. No longer was it enough to lob shells across the front lines into enemy territory. In Vietnam the radius of fire might well include an entire 360-degree circle.

Simply stated, the solution was the fire support base (FSB), a rapidly constructed artillery position occupied by air-delivered artillery pieces and defended by a minimum of infantry. The fire support base concept, while involving certain risks, clearly added to the flexibility of the tactical unit. The concept called for artillery to provide close and continuous fire support for the infantry, as well as for other fire support bases. Ideally, the fire support base would be located on a point of high ground overlooking the operational area. FSBs were normally occupied only as long as the maneuver elements were within range of the friendly artillery firing fan. As the ground forces maneuvered out of their range, new fire support bases were constructed, and the artillery was moved to the new locations to continue to provide fire support to the maneuver elements.

Adeptness And Experience

By the development of a simple and responsive system of air and ground control, the infantry commander in Vietnam was able to weave artillery and close air support quickly and effectively into his pattern of ground maneuver. By utilizing the fire support base concept, infantry commanders were able to achieve maneuverability without sacrificing their supporting artillery firepower. Additionally, the ability of artillery forces to rapidly shift their positions made area saturation by artillery a reality for the first time in many combat areas.

Construction of mutually supporting firebases called for adeptness and experience at fire coordination, resupply operations and communications, as well as tactics and strategy. As soon as a ground commander's tactical scheme of maneuver indicated the need for using the fire support base concept, there were certain pre-D-day requirements that had to be accomplished. A maximum team effort by units of varying specialties and capabilities was required in order for the FSB concept to be effective. Establishing close coordination and cooperation between the infantry unit commander, the artillery unit commander and the engineer commander as quickly as possible was mandatory.

Visual Reconnaissance

The engineer commander had to act immediately upon being informed of the operation's time, location, and the size and composition of the units that would occupy the FSBs he would construct, all of which dictated the size of the FSBs required. A preliminary study of the terrain -- using maps, any available photographs of the operational area, and all reconnaissance data obtained from previous inserts into the targeted zone -- had to be made. A complete visual reconnaissance, however, was the most effective means of planning the engineering personnel, equipment and demolitions required to fulfill the engineering mission.

During the visual reconnaissance, the engineer commander determined the suitability of the staff-proposed FSB sites with regard to the economy of engineering efforts that would be required for development as compared to other tactically suitable sites; the area of plane surfaces suitable for helicopter landing zones; the extent of foliage, brush and undergrowth; and the approximate number and average diameter of trees on the proposed sites. Using data gathered from all these sources, the engineer commanders were able to make detailed recommendations on site selection.

Once the FSB sites were selected, reconnaissance elements were first sent in to determine whether enemy forces were an immediate threat. To provide such intelligence, UH1E helicopters were equipped with the XM-3 Airborne Personnel Detector, or "People Sniffer." As the pilot flew at treetop level, the 65-pound device monitored the air rising from beneath the jungle canopy, detecting human ammonia effluence or the combustion products associated with human activity such as cooking fires and vehicle exhaust. Recon teams visually verified the mechanical intelligence.

Layered Landings

A 13-man team was loaded aboard a helicopter. Part of a flight of six aircraft that penetrated the target zone simultaneously from different directions, each of the helicopters made up to six touch-down landings in the target area, masking the single team insertion during one of the touch-downs in the proposed FSB site. In securing the objective, the recon team scouted not only the immediate area of the proposed landing zone but also access routes and points of vulnerability that might cause it to become untenable. Using an explosive innovation known as the Helo Trap Weapon, the recon team cleared the landing zone of anti-personnel and helicopter booby traps so that the security forces and engineering units could be safely landed.

Once the landing zone was cleared of booby traps, an infantry security force was landed, replacing the recon team, which was extracted. The security force set up in a 360-degree defensive perimeter around the support base and immediately began to dig in, creating defensive postures, clearing fields of fire and conducting patrol operations.

As soon as the security force was firmly in place, engineering personnel and their initial equipment and supplies were delivered. Typical supplies might include 1,000 pounds of composition C-4 (white plastic explosive); 10 cases of Bangalore torpedoes; 5,000 feet of detonation cord; 100 M-16 fuze lighters and hand tools, including axes, brush hooks, machetes, shovels, posthole diggers, log carriers and half a dozen gasoline engine-driven chain saws.

Swinging Axes

On entering the landing zone, engineers gave first priority to clearing all underbrush, foliage and dense growth in order to facilitate ease of movement and the placement of demolitions charges. Underbrush and vegetation were cleared using a combination of hand tools and demolitions. The operations were not carried out without difficulties.

Captain David F. Winecoff, the commander of Hotel Company, 2nd Battalion, 9th Marines (H/2/9), in 1969, commented on his experience constructing Fire Support Base Razor in the Da Krong River valley of northwestern I Corps: "We went in with enough power saws and axes to do the job if we had the experienced people to work these things. We were the ax swingers, but I found out that there were very few people in Hotel Company who knew how to swing an ax properly. We immediately proceeded to bust about 50 to 60 percent of our axes before we found a few people who knew how to swing axes. It was only through the cooperation of the engineers and all hands concerned in Hotel Company that...we got the fire support base opened up in time."

Colonel George C. Fox recalled: "Senior commanders quickly learned that this new generation of Marines, with a handful of exceptions, had no knowledge of 'woodsmanship.' Gone, too, were the days when every American boy knew how to fell a tree. We had a few men from the Northeast (New Hampshire and Vermont) and the Northwest (Oregon and Washington) who knew what they were doing. Most had never seen an ax! Dave Winecoff, myself, and one of his gunnery sergeants ended up holding 'ax school' right on Fire Support Base Razor! And the power saws were small commercial models never intended for this type of heavy work and continuous operation. We probably had 90 to 95 percent failure of this item, although many were temporarily repaired on the scene. Here, the mechanical ability of the new generation paid off!"

Clearing By Demolitions

Once the light brush, small trees and debris had been removed, engineering personnel commenced the removal of the larger trees. As noted by Colonel Fox, experience proved that the gasoline engine-driven chain saw could not adequately cut the larger, extremely hard teak and mahogany trees native to the northern and western I Corps areas. Additionally, air and artillery strikes had filled the trees with shrapnel that would ruin even the best equipment available. Therefore, the most suitable method for felling trees was through the use of demolitions -- hence the thousand pounds of C-4.

Trees were generally cut in groups of 15 or so by utilizing a nonelectrical dual primed firing system and ring main to avoid the possibility of misfires. Trees in the proposed landing zone were taken down as quickly as possible. Felled trees were cleared from the area immediately and then set aside for later use as bunker covers.

Clearing and resupply operations were run simultaneously, a great advantage to a unit in the assault phase of operations that was attempting to achieve a rapid buildup of forces before the enemy could react to its presence. In order for helicopters to deliver sling-loaded supplies, the trees only needed to be cleared sufficiently for the rotor blades to clear the brush.

Next: Clear Approaches

Copyright (c) 2000, PRIMEDIA Enthusiast Publications, Inc.

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