336. Memorandum From the Director of Intelligence and Research (Hughes) to Secretary of State Rusk 1
SUBJECT
- 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.
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. [Page 659] 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.
- Source: Johnson Library, National Security File, Country File, Vietnam, 5 EE (1) Laos, 10/67–12/68. Top Secret; Exdis.↩
- Not printed.↩
- 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)↩