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The following Telegram from the Embassy in Laos to The Department of State, on July 6, 1967, outlines assurances made to Souvanna and answers a specific question he had concerning the capabilities of MSQ-77.  TSQ-81 was actually installed, it is a more compact and mobile version of MSQ-77. The TSQ-81 was designed by the Reeves Instrument Corp in New York on very short notice.

296. Telegram From the Embassy in Laos to the Department of State/1/

Vientiane, July 6, 1967, 0830Z
/1/Source: Department of State, Central Files, POL 15 LAOS-US. Top Secret; Priority; Exdis. Repeated to CINCPAC, COMUSMACV, and JCS.
108. Ref: State 909.

/2/In telegram 909 to Vientiane, July 4, the Department of State agreed that in the "worst" case of full-blown disclosure of the installation at Site 85, the United States would accept Souvanna's denial of prior knowledge and in turn remain silent or say "no comment." (Ibid.)

1. Souvanna agreed this morning to installation of MSQ-77 at Site 85. I assured him that:

a) All USAF markings would be removed from equipment,

b) Detonators would be affixed to permit immediate destruction in case of imminent danger,

c) Personnel would be under civilian cover,

d) Maximum measures would be taken to camouflage against detection from the air, and

e) Electronic camouflage would be undertaken by scrambled transmission to relay aircraft over Gulf of Tonkin.

2. In turn, Souvanna accepted agreed formulation on public relations posture. If there are deniable allegations concerning presence of this installation, he will say "I have no knowledge of such facility in Laos". If it is blown in undeniable fashion, he will say "I did not know it was there". In both instances, U.S. can either remain silent or say "no comment." This should bring all of us angels together on the head of the same pin.

3. Souvanna also asked whether this radar could function to detect violations of Lao air space. There have been contributing reports of unidentified aircraft in vicinity Plain des Jarres. (Just last evening, we made an abortive effort to intercept a reported Ilyushin 18 near Moung Kheung.) He says he fears these are ChiCom planes used to provide liaison with ChiCom Mission at Kheng Khay. I told him I thought this could probably be worked into installation, but it might degrade our communications security.

4. Please provide technically sound reply whether MSQ-77 could serve as early warning radar, or, in a pinch, as intercept control./3/ If so, would this cause shift from agreed line of sight, scrambled, and relayed emanation pattern.

/3/In telegram 3371 to Vientiane, July 8, the Department of State informed Sullivan that the early warning and intercept control capacity of the equipment of MSQ 77 "is so limited as to be of little or no use in detecting violations of Lao airspace." (Ibid.)

5. Assume JCS will now direct 7th AF to make contact with my Air Attaché to get this project moving. Timing and other factors involving sensitivity will be coordinated by this Embassy.

6. I would like assurances that info on this installation will be held on the closest need-to-know basis, that all personnel who do know will be briefed on need for maximum security and that all efforts will be made to avoid indications of its location on maps, charts, or instructions. If operational strike units can function without actually knowing exact location of MSQ-77, this would clearly obviate possibility that captured air crews could become source of compromising information.

7. Please advise steps being taken to accomplish objectives of para 6 above. It should be made clear that a compromise might result in a requirement to remove the installation if it, and the RLG, are sufficiently embarrassed.


And so... the installation started... and was completed.  If my memory serves me correctly, it became operational during the first week of November, 1967

Trailers and Electrical Equipment at Site 85

Lima Site 85.

The trailer with the open door housed the communications equipment. Trailer to the left was the TSQ-81 with Radar Dish camouflaged. To the left were electrical generators and frequency converters.  The living quarters is shown in the foreground. The outhouse was approximately 20 feet to the left of the living quarters.



January 12, 1968, two AN-2 Colts, made in the Soviet Bloc, (Pictures) attempted to destroy Site 85 by dropping 120mm mortar shells from a hole in the bottom of the aircraft (they were armed by the slipstream).  There are other opinions of what the AN-2's had in the way of munitions, but this seems to be the general consensus of opinions. The attack was basically ineffective.  The TACAN installation was down for a few days due to a damaged antenna.   A few power cables had to be repaired.  The TSQ-81 was not harmed.  One AN-2 crashed into the side of a mountain as a result of small arms fire from the ground,  the other was brought down by an Air America sharpshooter (Glen Woods), with a rifle, while airborne(Newspaper Article).  Glen was KIA on 12 August 1969. There were two other AN-2's in the area,  orbiting at a higher altitude. They made no attempt to attack the site.  Operations continued but there were other problems, as indicated by the Memorandum from the Country Director for Laos and Cambodia  to the Assistant Secretary of State for East Asian and Pacific Affairs on February 1, 1968.

330. Memorandum From the County Director for Laos and Cambodia (Herz) to the Assistant Secretary of State for East Asian and Pacific Affairs (Bundy)/1/
Washington, February 1, 1968.
/1/Source: Department of State, EA/Vietnam, Laos, Cambodia Files: Lot 75 D 394, TS. Top Secret. Drafted by Slutz. Copy sent to Habib.

Enemy Pressure on Site 85

1. The most recent reports of enemy action around Site-85 (Phou Pha Thi) indicate that an attempt to seize the site is imminent. Two key outposts defending the approaches to Site-85 have already been taken by the North Vietnamese and pressure is continuing to close in around the site.

2. Over a year ago when Vang Pao attempted to defend Site-36 (Na Khang), his troops suffered a great number of casualties. At that point he decided never again to commit his units to the all-out defense of a position. That tactic is still being followed and, while his units will continue to defend Site-85 as long as possible, he does not intend to accept heavy casualties in exchange for real estate.

3. As you know, the TSQ 81,/2/ as well as a TACAN facility, is located at Site-85. When the decision was made to install these facilities it was understood that no last ditch stand would be made to defend them. Although this equipment is costly, it is expendable--the men who service it are not and they will be removed prior to the fall of the site, if the situation becomes hopeless.

/2/TSQ 81 was the mobile version of MSQ 77.


General Vang Pao
was commissioned to defend Site 85 with his
Hmong troops.



Enemy Contact Locations at Site 85 from 1 dec 67 to 12 Jan 68

A Radar composite showing enemy locations at Site 85 as of 12 January 1968.

The following Memorandum is from the Director of Intelligence and Research to the Secretary of State stating the importance of Lima Site 85, dated February 28, 1968.

336. Memorandum From the Director of Intelligence and Research (Hughes) to Secretary of State Rusk/1/
Washington, February 28, 1968.
/1/Source: Johnson Library, National Security File, Country File, Vietnam, 5 EE (1) Laos, 10/67-12/68. Top Secret; Exdis.

Significance of Phou Pha Thi (Site 85) in Northeastern Laos

This is in response to your request for information on the significance of Phou Pha Thi.

Equipment. Phou Pha Thi is the site of a very important US radar-navigational station for supporting US air operations in North Vietnam and northern Laos. Equipment installed at the site are:

TSQ-81--a portable version of the MSQ-77--an extremely sophisticated radar-navigational device used by US bombers for precision-bombing of targets in North Vietnam north of Vinh at night and in inclement weather. It has an effective range of about 200 miles (see map for area covered in North Vietnam)./2/ Installed on November 1, 1967, it is the only device of its kind in Laos. Two MSQ-77's are installed in Thailand, and two in South Vietnam.

/2/Not printed.

TACAN--a navigational aid which emits beams to help orient US aircraft operating primarily in northern Laos. It was installed about a year ago. There are three other TACAN sites in Laos, the nearest one to Phou Pha Thi being at Long Tien, south of the Plain of Jars (see map).

US Personnel. At any one time, there are 15 Americans stationed at the site: 12 to service the TSQ-81, two to service the TACAN, and one presumably to oversee the operation. As at the other TACAN sites in Laos, these individuals are USAF personnel, formally converted to civilian status as Lockheed employees for the duration of their tour of duty in Laos. There are three teams based on Udorn, each serving a five-day shift. Prime Minister Souvanna Phouma has authorized the stationing of US personnel at the TACAN sites, but he has not been told about the TSQ-81 at Phou Pha Thi.

Guerrilla Base. Pho Pha Thi, which is situated only 25 miles from Sam Neua town, has also served for some time as a major base for guerrilla operations. At present, about 700 Meo irregulars are based there to carry out forays into enemy territory as well as to man a defensive perimeter with a radius of about 12 miles. This perimeter has been breached during the past week.

Enemy Threat. The enemy is undoubtedly aware of the importance of the site as a radar-navigational installation and of the US presence there. The site was bombed unsuccessfully by North Vietnamese aircraft on January 12./3/ Since then, the enemy has been completing elaborate preparations, including the building of roads, to make a ground assault upon the site. Ambassador Sullivan believes that this will take place within two weeks. We believe that should enemy artillery come within range of the 600-foot airstrip, it would become extremely difficult to extricate the small US unit as well as the 700-man Laotian force.

/3/The attack was by two Soviet-manufactured Colt (AN-2) single engine biplanes, which bombed the site at 1:20 in the afternoon. The aircraft dropped 15 bombs of 250 lbs. wounding three Lao soldiers and one U.S. technician. The bombing resulted in slight damage to the TACAN antenna and temporarily closed it down. The TSQ-81 continued to operate. Both planes were lost after the raid. One crashed into a ridge after being hit by small arms fire from the ground, and the other was shot down by a sharpshooter with a rifle from an airborne Air America helicopter. (Telegram 3779 from Vientiane, January 12; Department of State, Central Files, POL 27 LAOS)    

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