Attack of Bunker Complexes

To successfully attack and destroy an NVA bunker complex similar to the type encountered at Khe Sanh required methodical, repetitive reconnaissance by aerial observers and photo interpreters, and coordination with cognizant Direct Air Support Center to ensure target/ordnance matching and the timely arrival of aircraft.

There was little evidence that the NVA actually lived in their trenchlines. Instead, large bunker and trench complexes were constructed adjacent to the main comminications/fighting trench system. The living areas were generally located within 200 meters of the primary trenches, either in heavy grass and scrub brush, or under a canopy of trees. In all cases these living areas were very well camouflaged and showed considerable care in their placement and construction. It is of significance that the NVA soldiers were often observed moving about freely in the main trench system during the day, but were not seen elsewhere. Consequently, many of the living areas went undiscovered. Movement from the living area to the forward trenches commenced during the early evening hours, and excavation continued throughout the night. By morning, few soldiers were to be observed remaining in the trenches.

Factors Affecting target Acquisition

In order to accurately assess the damage inflicted on the enemy at Khe Sanh, it should be pointed out that the difficulties of target acquisition undoubtedly played a large role in determining the type and amount of ordnance employed in each case. Factors affecting target acquisition ware grouped as:

• The counter-surveillance screen of camouflage and frequent movement.
• Utilization of adverse weather to cover large troop movements, trenching, and construction of fortifications.
• The effect of Mountainous terrain on ground observation.
• The environment created by antiaircraft and automatic weapons fire against observation aircraft.
• Limited observation aircraft assets.

If results were not observed, a prediction was made of the outcome of weapons employment and the probable effects of a given system versus a specific target. Weapons effects manuals addressed problems of damage within certain confidence intervals, relying on the assumption of normal distribution for fall of shot, Circular Error Probable (CEP) miss-distances for bombs, etc. In many cases however, weapons employment was based on intuition and experience. The requesting agencies relied on the intuition and experience of the observer, the FAC and the pilot in selection and delivery of ordnance.

The proven difficulty of locating and destroying a reveted artillery position was best illustrated by the example of causing damage sufficient to force evacuation of the piece for repair (defined as an F-Kill). Table 1 depicts the acceptable miss-distance to achieve an F-Kill on a 152mm artillery piece.

The significance of these small F-Kill miss-distances can be placed in perspective by consideration of the Circular Error Probable (CEP) for bombs (Table 2) delivered visually at 500-kts in a 45 degree dive from various altitudes and for artillery (Table 3) at various ranges.

The foregoing was not intended to degrade the usefulness of the weapons systems employed. Quite obviously, the magnitude of damage inflicted at Khe Sanh was completely unexpected by the enemy. Rather, the intent was to empahsize the extreme difficulty encountered in the successful attack of hard point artillery targets.

Conclusions

From the compiled data of the various bunker complexes and trench systems at Khe Sanh, certain facts could be summarized:

• Construction consisted of locally available materials.
• Entrances to bunkers were kept as small as possible and were at right angles to the main axis of the bunker.
• The most common bunker measured 4x6x4 feet and was rectangular shaped with 18-24 inches of overhead cover.
• Overhead cover consisted of logs covered with a grass matting and earth.
• Camouflage was deliberate and detailed.
• Bunkers had a low silhouette, and blended with the terrain and foliage.
• Extensive booby traps were not encountered.
• Bunker complexes were located on reverse slopes adjacent to trails and water sources.
• Positions were mutually supporting and interconnected by trench systems or communications wire.
• Trenches were serpentine-type, 2x4 feet, with directional changes every 20-30 feet.
• Trench complexes were not used as living areas; they provided access to living areas and/or assault positions.
• Antiaircraft and automatic weapons positions were integrated into the trench and bunker complexes for protection and to deny observation.
• Small, individually camouflaged holes along trail networks indicated the presence of a large unit in the area.

Lessons Learned

• Avoid piecemeal expenditure of ordnance against scattered targets.
• When areas of high activity were located, isolate and expose them with stand-off fuzing, napalm and incendiary ordnance, then attack the position with the type and quantity of ordnance best suited for destruction.
• Reduce delivery CEP by employing more observation aircraft, and using area type munitions such as the CBU and BLU series against personnel targets.
• Deny the enemy the use of his bunkers and living areas through intensive observation exposure and CS contamination.
• Utilize lapse or neutral atmospheric conditions for CS employment against personnel targets.
• Emphasize surprise through random selection of high intensity areas of activity.
• Increase delay fuzing sensitivity for soft soils.
• Employ surprise fire during periods of reduced visibility.
• Utilize incendiary munitions in lieu of napalm for exposing fortified areas in high grass.
• Use observed fires whenever possible.
• Thoroughly search NVA trench systems for living bunkers prior to expending large quantities of ordnance on the trenches alone.
• Consider selection of a delivery system which will place persistent CS in selected portions of the trenchline to deny its use as an attack position, or force a new system to be constructed.
• The aerial observer (AO) must be permitted to conduct a methodical reconnaissance of every suspected position to insure positive location and identification of living areas. Once they have been identified they must be further exposed and reduced. Pilot accuracy increases greatly when he is able to visually identify and follow his target, and aerial observers should encourage the pilots of supporting aircraft to make several dummy runs from different headings until the pilot sees the target. When hostile fire prevents low level observation or dummy runs, the AO and the supporting aircraft pilot should pick a prominent reference point close to the target to be used in conjunction with the marking smoke.
• Initial runs should be made with hard ordnance employing 'daisy cutter' fuze, or napalm. Artillery white phosphorus can be used to burn away the grass or mark the entire area. The important point is to first expose the target by destroying the surrounding vegetation, then conduct systematic attacks against the bunkers employing heavy artillery and air ordnance with delay fusing.