Fire Support Base Development
by Major Robert V Nicoli, 9-69
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Fire Support Base Development
NOTE: At the time of this writing Major Nicoli was serving a 2d tour in V'nam, is operations officer, 3d Engineer Battalion. He commanded a company there in 1965. He graduated from Stonehill College prior to being commissioned via the OCS program in 1958.
Built by engineers, defended by the infantry & manned by artillery, the fire support base is a successful example of USMC flexibility and response.
Throughout its history, the USMC has sustained a record of achievement and innovation which has cast it in the enviable role of the most effect mili force known to our country. In V'nam the USMC's ability to innovate - to meet the needs of the moment were again tested. during the latter part of the summer of '68 the 3d Marine Division [3MD], commanded by MajGen Raymond G Davis, introduced the fire support base [FSB] concept in northern I Corp Tactical Zone [ICTZ]. The Marines found themselves operating in mountains, swamps, forests & jungles - terrain not conducive to fixed lines of communications & mechanical means of transportation other than the helicopter. A concept of operations [ops] involving fast-moving, far-ranging units was necessary. A new method of providing fire support [FS] concept into northern ICTZ. Very basically, a FSB is a rapidly constructed artillery position defended by a minimum of infantry. the infantry & tactical elements operate within the protective fan of the artillery, & as presently applied in the 3MD, the FSB's themselves offer overlapping artillery support to each other and protection for several Landing Zones [LZs]. At the present time there are a rapidly increasing number of FSB's strategically located throughout western ICTZ. The tactical requirement for this innovations is indeed a very sound one.
Planning & Development of FSB's.
The type of warfare in which we are presently engaged in V'nam necessitates rapid response to any action by the enemy. If artillery were to be located in fixed positions in rear areas, our infantry forces would be deprived the benefit of this support. By utilizing the FSB concept we are able to achieve maneuverability or mobility along with firepower. In addition, the ability of artillery forces to displace & conduct ops throughout the western ICTZ area has made area saturation by artillery a reality. As soon as the tactical scheme of maneuver indicates a need for a FSB, there are certain pre-D-Day requirements which must be accomplished. It is mandatory that close coordination & cooperation be established at the earliest possible time between the engineer commander, the artillery commander & the infantry commander.
The 1st things to be concluded by the engineer commander are:
the time & place of their op;
the size of the area to be cleared;
the size & composition of the unit which will occupy the area;
a study of maps & any available aerial photographs of the area;
a study of all recon info obtained from previous inserts.
Once these sources of info have been thoroughly exhausted, the next step is to arrange for a visual recon, by air, of the proposed site. This visual recon is normally conducted by the engineer officer [EO], the infantry & artillery commanders & the air officer. The importance of the visual recon cannot be over-emphasized. A complete visual recon by the engineer commander is the only effective means for adequately planning personnel, equipment & demolitions requirements. Over the past 8 months, the 3d Engineer Battalion [3EB] has found that on those occasions when engineering difficulties or problems arise during the constructions of a FSB, there problems can almost always be attributed to the fact that the engineer commander has not been afforded the opportunity to conduct a visual recon. During the conduct of the visual recon the engineer officer will attempt to determine:
the suitability of the site with regard to economy of engineer effort as compared to other tactically suitable sites;
the area of plane surfaces suitable for helicopter LZ's;
the extent of foliage, brush, & undergrowth;
the approximate number & average diameter of trees.
With the info gained from the visual recon, the EO is able to make intelligent and beneficial liaison with both the artillery & infantry commanders. By contacting the artillery commander who will occupy the position, the EO now will be able to determine:
the approx location & size of gun positions;
the approx size & location of ammo storage areas;
By consulting with the infantry commander, the EO will insure that he is familiar with the tactical movement of personnel & equipment on and around the FSB site itself. There is a considerable amount of activity on a FSB during the early phases of development. It is the obligation of the EO to advise the infantry commander that excessive numbers of personnel & equipment moving about on a FSB during the early phases of development only hinder and delay demolitions ops. This 1 area constituted quite a problem in the 3MD during the 1st few months of the FSB program, & it was a problem on the FSB's 1st developed in the 1st Marine Division [1MD] TAOR. Experience indicates that the reason for this problem stems from an overeagerness on the part of the infantry for speed during the op. When infantry commanders of the 3MD were indoctrinated regarding the engineer requirements on a FSB, this particular problem disappeared rapidly. A related point & a possible area is the matter of resupply once the development of the FSB begins. At this point in his planning, the EO should insure effective liaison with the S-4 of the unit supported. Particular emphasis should be placed on the matter of identifying engineer resupply materials & establishing priorities for these materials. All too often, valuable time is lost when the wrong item is delivered in response to a resupply request. This will only be avoided if the EO insures that the S-4 of the supported unit properly identifies & serialized "on call" materials located at the staging line at the logistical support area. This is a very simple matter in accordance with good logistical support procedure, but it is too often overlooked, resulting in valuable time lost.
At this time consideration should also be given to the matter of demolitions materials & engineer tools required for the project. With regard to demolition materials, the 1st thing that must be realized is that the variance in the size & quantity of growth on the specific site will determine the amounts & types of class V materials to be used. The 1st task which must be completed on any FSB project is the clearing of an area suitable to take both internal & external helicopter lifts. This is the task with which the engineer personnel will be most involved during the 1st few hours of the op. The 3EB, for planning purposes, has established an allowance of demolitions to be lifted into the site immediately for the purposes of developing the LZ. These quantities have generally been confirmed by actual ops over the past 8 months:
1000 lbs of composition C-4;
10 cases of bangalore torpedoes;
5000 ft of detonating cord;
500 ft of time fuse;
300 non-electric blasting caps;
100 M-60 fuse lighters.
Along with this allowance of demolitions, specific items of engineer equipment and hand tools are required to be used in clearing the area of trees & brush. Modified versions of both the pioneer tool kit, engineer squad & the infantry tool kit are also among the initial items in with the demolitions. The specific items from these tool kits which are of the most value in FSB development are the axes, brush hooks, machetes, shovels, post hole diggers, & log carriers. The gasoline engine-driven chain saw rounds out the list of those items initially lifted into the site. It is normal to plan to have from 3 to 6 chain saws. The final area to be considered in the pre-D-Day planning will be the personnel requirement. Experience indicates that from 1 to 2 squads of engineer personnel provide sufficient manpower to complete the mission. Prior to D-Day, the responsible tactical commander will insure that the proposed site receives adequate preparation fires. the EO should advise the infantry commander that excessive preparation fire will only further increase the difficulty involved in clearing underbrush as it results in an entanglement of trees & brush. Only as much preparation fire as it absolutely necessary should be called in on the proposed site. Engineer personnel, with their initial equipment & supplies, are inserted into the area by internal lift, if possible, or by rapelling, with supplies being lifted in by cargo net in an external load. Once engineers & equipment, with a small security force, are on the proposed site, clearing ops begin immediately. All underbrush, foliage & dense growth will be cleared immediately upon entry into the designated area. Such clearing is given 1st priority as it will make possible ease of movement & the placement of demolitions charges. Underbrush & vegetation are normally cleared through a combination of hand tools & demolitions. The use of demolitions in this situation is quite varied, & limited only by the imagination of the user. Many varied techniques have been developed, & the use of some of these techniques at times necessitates modifications to the initial allowance of demolitions mentioned earlier. In addition to the use of bangalore torpedoes, some other methods found successful in clearing underbrush are M-58 & shaped charges, & barb wire mines. It should be noted that the M-58 line charges, in particular has proven to be very effective. Used without the rocket assembly & primed non-electrically, it is extremely effective in clearing away light brush & debris. Brush hooks, axes, machetes & chain saws are used in conjunction with demolitions for clearing ops. Once ease of movement is obtained, engineer personnel commence the cutting of larger trees. Experience has proven that the gasoline engine-driven chain saw does not adequately cut the larger, extremely hard teak & mahogany tress native to the northern & western ICTZ area. The most suitable method for felling trees is through the use of demolitions, primarily C-4 or TNT if C-4 is not available. Different types of timber in various localities require varying amounts of explosives. For external untamped charges, the standard timber cutting formula of P= D2/40 has generally proven to be ineffective in the 3MD TAOR. The results of this formula must usually be increased from 20 to 50% to obtain the desired results. It is recommended that the EO conduct several test shots, utilizing the basic formula to determine the specific amount of explosives required for a specific timber. Trees can be removed by utilizing the external untamped method of placing charges, after cutting a notch in the tree with a chain saw, or by blasting, utilizing tamped charges placed in the ground at the root system. Once again, the use of demolitions for this task is limited only by the imagination of the user. Some other methods proved effective in removing timbers are shaped charges placed against & perpendicular to the tree; counter force (or ear muff) charges in which half the charge is placed on each side of the timber directly opposite each other (for timbers of less that 4 ft in diameter); strip charges placed completely around the timber & close to ground level. Trees are normally cut in groups of 10 to 15 utilizing a non-electric dual primed firing system & ring main to avoid the possibility of misfire. As trees are felled they are cleared from the area immediately, sectionalizing them if necessary, & using a labor force of infantry personnel if available. These timbers should not simply be discarded, but selected ones set aside for such use as bunker covers during the later development of the FSB. It is during this phase of development that the EO must pay particular attention to the requirement for helicopter LZ's. In order to permit the most effective use of helicopters for resupply, the EO must insure that the ground approach to, & exits from the LZ are at least as wide as 2 rotor diameters. These approaches must remain clear of communications wire & all other obstacles. There should also be an area clear of high obstructions (30 ft or higher) extending at least 150 ft in the direction of the approach & exit paths. This distance gives helicopters an opportunity to gain forward velocity before they must commence climbing. In order to insure that these glide path requirements are met, the 3EB requires all platoon leaders & sergeants to be particularly familiar with the use of the clinometer or topographic hand level, and to use this instrument during FSB construction. the EO must also insure that the site of the LZ itself is large enough to allow clearance for rotor blades, & also that there are no stumps or growth on the site exceeding 1 foot. I might add here that it is the policy of the 3EB to cut all trees in the area of the LZ as close to ground level as possible. Once the initial LZ is established, additional engineer equipment & demolitions are lifted in to facilitate the development of gun pits & ammo berms. The additional demolitions are usually large amounts of shaped charges (40 or 15 lb), cratering charges, & composition C-4, & the additional equipment is in the form of the Case 450 heliliftable tractor & the Case 580 heliliftable tractor with back how attachment. The standard gun pit requires an approx 30-foot diameter hole with a 3-foot high berm. With a 30-foot diameter hole it is possible to achieve 360 degree coverage by either 105mm or 155mm howitzers. In a pit this size, when turning a 155mm, some movement of the gun back & forth is necessary in order to turn it and still keep it in in the center of the parapet. For this reason, some artillery commanders have required parapets of up to 40 to 60 feet in diameter for 155mm's. Of course, this is dependent on the amount of space available on the site itself. The gun pits are constructed through the combined use of demolitions, hand tools & the Case 450 heliliftable tractor (bulldozer). Whether the emphasis will be on demolitions or engineer equipment is solely dependent upon the composition of the soil at the project site. In areas in which the soil is highly compacted, rocky or difficult to penetrate, it is desirable to prepare the area for the Case 450 tractor than through the use of demolitions. One technique which has proved very effective is to place 4 40-pound or 15-pound shaped charges 15 ft apart in a square formation & one in the center. These charges are dual primed with a non-electric firing system & detonated simultaneously from a ring main. After the detonation, a 40-pound ammonium nitrate cratering charge or 20 lbs or less of C-4 or TNT, depending upon the soil composition, is placed in each resulting hole & tamped with earth. The cratering charges are also primed non-electrically & detonated at the same time. The resulting detonation will produce a hole approx 30ft in diameter & 3 to 4ft in depth. The Case 450 tractor is then used to clear the area of loose earth & shape the pit to the desired configuration. In areas in which the solid is not highly compacted or very rocky, the Case 450 tractor can be employed with the prior use of demolitions to prepare the area. Together with the construction of gun pits, ammo berms are prepared. The configuration of the ammo berms will vary dependent upon the desires of the artillery commander & the amount of space available on the FSB. The Case 580 heliliftable rubber-tired tractor with back hoe attachment is ideally suited to the construction of ammo berms. The 580 is normally helilifted into the area following the 450. At this point in the development of the FSB, the 1st guns & additional artillery personnel begin to arrive by helicopter. Guns are placed in the parapets on a pad, usually constructed on M3A1 matting, & the gun crews set about the work of preparing themselves & their equipment to accept fire missions. We must recognize that at this point activity on the FSB is greatly accelerated. The engineers continue to develop the position by constructing additional parapets, ammo berms & bunkers if necessary. the command element of the artillery battery is busily setting in their fire direction center, & guns and ammo begin to arrive in fairly rapid succession. The engineer functions previously described are repeated until the desired numbers of facilities are developed. The engineer participation in the development of the FSB is fast coming to an end, & engineer personnel & equipment can now be systematically withdrawn & returned to the respective company areas for rehabilitation and preparation for the next commitment.
Normally a small detachment of engineers does remain on the FSB to assist in further developing the position through the installation of airfield matting on the LZ's, additional tree cutting on the periphery to ensure that fire is not masked, & various tasks of this nature. As you can see, a great team effort is required in the development of a FSB, all directed toward 1 end - to ensure that the Marine infantry receives the utmost support in delivering its deathblow to the enemy. The engineer contribution to this effort is of utmost importance. To be effective the FSB must be completed on a strict time schedule. The efficiency & proficiency of the engineer effort makes compliance with this schedule a reality. Secured by the infantry, built by the engineers & manned by the artillery, the FSB stands ready to support the infantry as it expands its ops into enemy territory. The FSB concept has expanded the war to all parts of RVN, depriving the enemy of staging areas & infiltration routes. It allows the infantry to move throughout the ICTZ area while retaining the protective fires of friendly artillery. It is a team concept embodying mutually supporting forces within the USMC's flexibility & response.