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Contemporary Historical Examination of Current Operations


(9 AUGUST 1968)


Prepared By: Captain Edward Vallentiny

Project CHECO, 7th Air Force, DOAC


An ADC ambush some 8kms southeast of Phou Pha Thi had killed a small party of North Vietnamese on 18 February. Apparently, one of the victims had been an NVA officer, and recovered from his body was a small notebook which contained detailed information concerning enemy plans and strong points for the coming attack on Phou Pha Thi.

Information from the notebook yielded the following data in addition to enemy positions:

- Three NVA and one PL battalions were to make-up the attacking force. - Final battlefield reconnaissance was to be conducted on 22 February. (CAS estimated the attack would commence on 23 February). - The enemy used the word "TACAN" as it appears in English and was aware of its exact location. - The main assault force was to be one NVA battalion attacking from the northeast; the other battalions were to attack the main trails to Phou Pha Thi. - Stocks of ammunition for all heavy weapons were low and re-supply was needed.

Friendly response to enemy activity and the new information was rapid and effective. Already on 17 February the Ambassador at Vientiane had authorized visual and armed reconnaissance missions alone Route 602 eastward from Phou Den Din and more targets were authorized around Site '85. Small patrols were dispatched by the ADC defenders to select targets in the local area for artillery fire and airstrikes.

Special reconnaissance teams of General Vang Pao's irregulars were even ranging east of Sam Neua trying to identify depots supplying the enemy forces in the Phou Pha Thi region.

In addition, two 4.2 inch mortars and another 105mm howitzer were sent to Phou Pha Thi and the garrison was increased by fifty men.

Effective at 1800 on 21 February, the U.S. Ambassador to Laos authorized the LADC at Site '85 to task the TSQ facility to strike any target within a 12km radius of the peak of Phou Pha Thi. This authorization was limited in that strikes could be placed no closer than 500 meters from known villages and that Commando Club strikes were still to be conducted via secure voice channels through the Radio Relay Aircraft (RRA). A list of nineteen still active villages accompanied the authorization.


Starting 20 February and extending to the fall of Site '85, early on the morning of 11 March, a determined air effort of constantly increasing intensity was directed in its defense. On 23 February, a message from the JCS to CINCPAC denoted that increased air support was "urgently" needed. From 20-29 February, 342 strike sorties hit within 30km of Site '85, most much closer than 30km.

In addition, other sorties struck east of Sam Neua against depots and supply concentrations. The latter attacks hit outside of the 30km area and were not included in totals listed above.

Route 602 was among the targets attacked, but the enemy had already assigned over 400 road workers the taks of keeping this vital line open. Later, bulldozers were also brought in. Except for intermittent closures due to road cuts, the enemy continued to use this artery. There was no doubt that airstrikes and artillery fire were retarding enemy activities, but they were not eliminating his presence or pressure within the 12km defensive perimeter around Site '85.

An unofficial estimate by an unnamed staff officer in one CAS report dated 25 February 1968 summed up the status as of that day and was extremely prophetic of coming events:

"As a result of the enemy's penetrating the 12km radius around Phou Pha Thi in force and occupying key positions within the lower right hand quadrant of this perimeter as well as positions just outside the perimeter at Phou Den Din, he represents an imminent threat to the security of the TACAM site and other installations at Phou Pha Thi. It is clear that the enemy will continue to consolidate his gains in the Phou Pha Thi area during the next two weeks while making arrangements for his final assault by three or four battalions. If, however, ADC units continue to harass successfully the enemy on the ground and if aircraft continue to strike enemy concentrations in and around Phou Pha Thi and in the area east of Sam Neua, the TACAN and other sites at Phou Pha Thi will continue to be viable for the next two weeks. It is not possible to predict, however, the state of security at Phou Pha Thi beyond 10 March because of the enemy's willingness to continue to escalate his co!mmitment in this area".

The American Ambassador in Laos was impressed with this estimate and commented on his feelings concerning Site '85 in a 26 February telegram to the Chief of Staff, USAF.


"... Enemy forward movement (toward Site '85) has been inexorable over the past months and neither air or ground resources which are available to us appear adequate to deter his intentions..

"... Although we are not ... throwing in the towel, we believe you should be aware of our current estimate that we may be able to assure security of this site for no more than the next two weeks.

"... You will recall that, when we arranged this installation, I made it clear that our principal defense effort would rest upon guerrilla units who operated with mobile tactics and that we could not ... guarantee a static defense. Our irregular units in this area are already stretched thin and have many other significant obligations related to the defense of population centres which make it impossible for us to look with any great hope upon the chances for effective reinforcement. Therefore, the moment of truth may be approaching for this site.

"... The TSQ is using its own inherent capabilities in the defense effort. Airstrike sorties are being provided in respectable numbers. But, in the final analysis, it seems doubtful that the site can be held in the face of consistent enemy determination.

"... Therefore, we are in touch with USAF authorities on evacuation and destruction plans. We are fairly confident both should be able to be carried out in orderly fashion. Moreover, we are examining possibilities of finding another useful site in the same general area which will provide roughly the same coverage."

As conceived in evacuation plans, the decision to evacuate was reserved for the Ambassador, Vientiane. First priority of evacuees was allocated to the 13 TSQ/TACAN personnel; however, enough helicopters were to be provided to permit a total of 155 to be lifted out.

The others, guerrillas, were to be extracted when the Local Area Defense Commander deemed appropriate.

Five helicopters, three USAF and two Air America, were designated as the force required to accomplish the evacuation.


To provide an immediate capability, the two Air America helicopters were to remain overnight (RON) each night at nearby Lima Site 98; USAF helicopters were to come from Thailand-based resources.

Subsequently, some USAF messages expressed the desire for Air America helicopters to RON at Site '85, not 98. However, this was not changed; it was feared helicopter presence at Site '85 would have provoked an enemy attempt to destroy these lucrative targets.

If they had been destroyed, the planned emergency lift capability would have vanished. But the point was well taken, for weather also might have disrupted the rescue flight from Site 98 to Site '85.

Following a decision to evacuate, the Ambassador was to notify 7/13 AF TACC at Udorn AB, Thailand who could in turn notify 7AF at Tan Son Nhut AB, Vietnam.

Weather permitting, 7AF was to scramble or divert four A-1 aircraft to provide cover for the evacuation, suppress enemy fire, and FAC for subsequent jet strikes.

The LADC and an attache-provided FAC were to help direct the strikes. The plan allowed a limited night evacuation capability (the RON helicopters at Site 98), but pre-supposed a daylight effort.

Enemy movements from 1-9 March are depicted in Figure 6.

Throughout the early days of March, enemy forces continued their advance, eliminating friendly pockets of resistance en route, until by 9 March, when the enemy deployed into what might be termed "jump off points", Phou Pha Thi was virtually surrounded, except for the northwest quadrant.

The enemy positions also threatened Site 111, only 8km north of Site '85.

Approximately four enemy battalions stood poised for the attack.


On 2 March, a review of the USAF rules of engagement for airstrikes around Site '85 revealed the changes which had occurred as the enemy threat mounted:

- Any target in the 12km defensive perimeter could be struck under FAC control.

- The restriction against strikes with 500 meters of villages only applied to Commando Club (TSQ) directed strikes, unless the target was validated by the LADC.

- Any Commando Club strikes could be diverted by the LADC to validated targets in the 12km perimeter.

- For a distance of 10km along Route 602, east of Phou Den Din, strikes were authorized under FAC or Commando Club control (this included "Gravel" and CBUs).

ENEMY CONTACT LOCATIONS (Vicinity Site '85) 1-9 March 1968

Site 111

Phou Pha Thi

Phou Den Din

Houei Ma

Site 179

Total 1000 enemy West to South Of Phou Pha Thi > Denotes Enemy Positions


- Use of CBU and "Gravel" was authorized anywhere in the 12km perimeter if validated by the LADC and if targets were at least 500 meters from friendly troops.

- The restriction of using only secure voice contact with supporting aircraft could be waived with Vientiane Embassy approval when under threat of imminent attack.

"Gravel Seeding" was accomplished on some confirmed supply routes east of Site '85 on 5 March. CBUs were used in the area around Site '85 in February. The use of CBU under Commando Club control was an innovation. Bombing tables were not available to be used in conjunction with the TSQ, but experience and "know how" of the 7/13AF personnel at Udorn AF Base in Thailand allowed them to improvise effectively until precise tables became available.

To facilitate around-the-clock capability of the TSQ facility, five more technicians were sent to Site '85 (the total number of Americans was now 19). More targets and sorties were allocated for the night operations.

On 5 March a message from 7AF to DOCO PACAF indicated conditions for evacuation, relocation of the facility, and remarked on the value of the site:

".... due to the desirability of maintaining air presence over NVA during present inclement weather period, Site '85 probably would not be evacuated until capture appeared imminent. The fact that complete security could not be assured in the original plan is noted ....".

In another message, later on 5 March, from PACAF to the Deputy Commander 7/13AF, with the commanders of 7AF and 13AF as informational addressees, CINCPACAF commented:

"Receiving daily reports concerning growing threat to Site '85. Difficult to evaluate situation from here. Request you consult CAS sources and provide me your estimate of threat, including anticipated time of attack, and friendly capabilities to defend.

"You are authorized to direct evacuation of site and destruction of equipment when in your judgement such action is necessary. Your plan, OPlan 439-68, is approved for this purpose. Keep 7th and 13th Air Forces and this headquarters informed of your intentions this regard. Insure that all preparations are made for emergency evacuation as required".


From 1-10 March, USAF carried out 314 strike sorties within 30km of Site '85. Over 76% of these were directed by the TSQ facility at Site '85. Among the targets struck frequently was the vital Route 602.

On 29 February, airstrikes had destroyed two bulldozers and killed the operating crews used to supplement road clearing operations.

Until serviceable bulldozers could be brought in, work was suspended. However, enemy resupply could not be halted; coolies, too, had been carrying supplies to enemy troops. One of their major routes, just north of Route 602, was subjected to a combined CBU/Gravel raid on 5 March.

Even though the weather in the vicinity of the site had deteriorated, the air attacks continued. But, it was becoming increasingly difficult to estimate enemy strengths and fix their locations because they had deployed into numerous small concentrations.

Evacuation Arrangements at the Site

On 9 March, at Site '85, the senior CAS adviser briefed the senior Air Force representative on the fact that an attack could come at any time. The evacuation plan was reviewed at that time and it was agreed that if evacuation was ordered, the TACAN/TSQ personnel would, if possible, proceed to the Command Post area near the helicopter pad (at lower elevation and 1/4 mile from the TSQ facility) where they would be picked up by helicopters.

If this movement was not possible, the technicians were to wait for the pickup at the TSQ site. It must be noted that a few feet from the entrance of the supply van (Fig.7), there were webbed belts or slings hooked up to allow the technicians to descent to a lower ledge a short distance down from the site level. Below this ledge, there existed a sheer drop of well over 1400 feet.

The CAS adviser's comment was that:

"The technique of personnel hanging over the cliff by straps was not discussed as a serious escape or evasion plan".

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