Talking Proud Archives --- Military

LS-85, Airmen left out on the limb, a leadership failure

September 10, 2017

By Ed Marek, editor

NVA moves in position for the attack

The rainy season of 1967 impacted NVA roadbuilding in Laos, but by October 1967 the rains had ended and the roads were dry. As a result, the NVA began aggressively repairing the roads, including the one to Phathi. Webb said "Hmong Road Watch Teams observed the activity and reported increasing amounts of heavy equipment working on (the roads)." Webb also said the RLA had made little progress on the ground in this region.

General Secord commented on this road in his book:

"A second piece of bad news came to us in November (1967) in the form of throwaway data, something so minor that it is often overlooked even by diligent analysts. Aerial photos showed what looked like a 'trace,' or the beginning of a mechanically cleared path, no wider than a goat trail, in the jungle about 25 miles from Site 85 at a place where several skirmishes had already taken place between NVA and Muong (Hmong) patrols.

"I immediately arranged for a FAC (Forward Air Controller) and CIA photo reconnaissance aircraft to take a closer look. The resulting evidence plainly showed that North Vietnamese workers were clearing brush and leveling terrain in an attempt to build a motor able road in the direction of Phou Pha Thi, a dagger aimed at the heart of Site 85. If it was allowed to get within 15 kilometers (nine miles) of the installation by the time the dry season commenced next spring (1968), artillery could be brought up to blast the facility off the map. If they wanted to absorb the losses necessary to occupy the mountain, the enemy could use the road to bring up men, supplies and munitions needed for a large-scale infantry assault. Either way, we believed, the key to preserving the site was to stop the road in its tracks."

Secord and his colleagues labeled the road "Route 602." Secord asked 7th Air Force to "whack 'em hard whenever they cranked up a tractor, to obliterate the construction in the early stages and make it crystal clear that we would simply not tolerate a road in the area." The 7th AF response was it had higher priority targets.

This 7th AF response was an indicator of what was to come, or not come, in the event the site were attacked. You will recall General Harris promised tactical air would be made available in such an event.

Webb also addressed the road building effort. He said the NVA, seeing the installations go up on Phathi, tasked its engineers early on to build a road from Sam Neua to Phathi. He said photo reconnaissance clearly showed the road-building progress. Webb then said:

"But the road's progress did not alarm many of the American leaders, because it was assumed the airmen manning the site could be evacuated and the radar destroyed should an attack take place. Ambassador Sullivan believed it also, although he didn't feel comfortable with a radar navigation facility being located on the summit of Pha Thi."

This assumption that the technicians could be evacuated in plenty of time prevailed in many quarters, and turned out to be a faulty assumption.

A moment to pause.

Chris Corbett's motorcycle ride from Sam Neua to Phathi, on "Rt. 602," with photos

A Facebook friend of mine whose name is
Chris Corbett has done a ton of motorcycle exploration of Laos, particularly the Ho Chi Minh Trail. I asked him once if he ever went to Ban Laboy Ford to take some photos for me to help me on a story, and he did. What a guy. I later asked him to do the same for Phathi. He was way ahead of me, and pointed me to his web page of photos showing his trip there.

Chris and a friend one day decided to go to Sam Neua and then take the road to Phathi. They knew it was once the LS-85 radar site and knew of the NVA attack on it. They found a road to the mountain and took it. I'll present a few of his photos. Please remember these photos were taken some 50 years after the demise of LS-85:

Chris is on the "turn-in" to the mountain. You can see the mountain center photo, about 4 kms (2.4 miles) away. He was worried about being stopped by either thieves or soldiers, but kept going.

Chris said he was about 30 meters away from the "Ladder" used to help carry supplies up the mountain when he took this shot.

And there she is. I believe the LS-85 site was on the top to the upper right. I further believe the sappers climbed up the rock cliff just below and slightly to the left of the site.

From up as far as he could get on his cycle, this is the view he had of the road to Sam Neua from Phathi.

He would later draw a few diagrams highlighting the road using Google Earth. I chose to show you this one.

I commend his
web site to you.

Okay, back to work.

A Hmong patrol apprehended two men near the summit dressed as Buddhist monks on October 20, 1967. They were carrying cameras. They were interrogated. The CIA people said their film had no photos of the site, the interrogation yielded nothing, and so they were released. In his book
A history of the Hmong: From Ancient Times to the Modern Diaspora, Thomas Vang reported, “In October 1967, two Pathet Lao spies dressed as Buddhist Monks were caught with cameras at the site.” Jane Hamilton-Merritt said the Hmong caught them and Vang Pao’s people interrogated them. Hamilton-Merritt said they confessed. She also said, as a result, Vang Pao felt the site had been compromised. Hamilton-Merritt said the USAF disagreed and concluded “the suspects were in fact bona fide Buddhist monks.”

The NVA began an offensive in northeastern Laos in December 1967. Two important events were in train in December 1967, shortly after LS-85's TSQ-81 became operational.

  • First, the enemy was probing the Phathi perimeter.
  • Second, the enemy was increasing the pressure on Nam Bac, an important government RLA garrison on Route 13 which went directly south into Luang Prabang.


As a result, TSQ-81 operators at LS-85 directed an estimated 75 percent of the 440 USAF sorties flown in December to strike targets in the region near LS-85, trying to save Nam Bac. Nam Bac was about 85 miles west-northwest of LS-85, the way the crow flies. The technicians knew what was going on: they directed sixteen of those sorties against targets around Phathi itself.

On January 10, 1968 a five man enemy patrol was seen at the base of the mountain.

On January 19, 1968 a Hmong patrol reported five battalions of NVA and Pathet Lao moving toward the mountain. US estimates had been that four battalions would be enough take the mountain.

Major Do said on January 22, 1968, the NVA sent out a six-man cell to climb to the summit and sneak into the TACAN site, the communications center, and the helicopter pad and confirm the enemy living and work locations. It also snuck into the Thai troop area, investigated four living and work areas, the medium and 12.7 mm gun emplacements, the mortar emplacements, the meteorological station and the defensive scheme. To do this sight unseen is remarkable, if true. Remember, there were some 200 Hmong at the base of the mountain and 100 on top, along with 300 Thais in the area. Major Do's rendition here is tough to believe, given those defenses. However, if true, it reaffirms people did not entertain a scenario where sappers would scale that cliff on the western side.

Recall the NVA launched a 30-minute mortar attack on January 30, 1968, which was written off as a “probing attack.” Also recall Major Do commented that by mid-February 1968 the "road" had been extended to within 2,000 yards of the mountain. He said that was close enough for artillery. Recall Major Secord had spotted that road in November 1967 and had asked 7th AF to destroy it, but was told 7th AF had higher priority targets

In a paper entitled “The Secret War in Laos: America’s Time in South East Asia and its Impacts,” prepared for California Polytechnic State University, Michael Prokop, a senior, wrote it was standard procedure for the NVA to build-up roads prior to a major attack. Citing Roger Warner’s book, Shooting at the Moon, Prokop said that this road construction toward LS-85 began on January 31, 1968. He further noted the NVA’s Tet Offensive in the RVN that began in January 1968 ate up much of 7th AF's air resources. As a result, “the road grew closer” to LS-85.

Kenneth Conboy wrote, “By the first two months of 1968, three battalions of Group 766 had infiltrated into the jungles around Phou Pha Thi, and slowly began to overrun surrounding outposts."

On January 30, 1968 the NVA detonated defensive mines on the approaches to LS-85. Following that, CIA said:

"The North Vietnamese settled into a containment perimeter approximately 12 kilometers (7.2 miles) in diameter around Phou Phathi. Engagements between the Hmong and the North Vietnamese became infrequent, but those few encounters that did occur involved enemy formations of at least company strength."


Recall the attacking force positioned itself in the vicinity of Muong-cau, in Muong-son District, about 40 kilometers (24 miles) northwest of Phathi. I believe Muang Cao (circled in yellow) on the map is Muong-cau in Major Do's description.

Major Do reported that at 1800, March 1, 1968 the attack team departed its base camp and moved for two days and four nights to the assembly point.

On March 7 the Party Committee confirmed the attack should proceed beginning between 0400-0500 March 11 (This might be March 10 in the US because of the International Dateline)

On March 7 the team split into its separate assault elements and advanced to the base of the mountain.

Movement toward the base of the karst encountered a few unexpected events, and halted. The force simply hid and conducted further reconnaissance to confirm the route up to the TACAN.

By March 9, the enemy had completely surrounded LS-85. Additionally, it conducted skirmishes along the baseline of the mountain. Webb said the CIA advisor at LS-85 briefed the USAF technicians that an attack could happen at any minute. They reviewed the evacuation plan and agreed the technicians would destroy the equipment and head down the footpath about 0.25 miles away to the helipad for evacuation. If unable to do that, they should remain at the facility and evade until help could come. They were told not to use the cargo nets draped out over the cliff hanging down to the ledge. They were told they should not consider that ledge a safe hiding place.

Webb added that some 300 sorties had been flown up to this point against the enemy advancing toward the mountain.

The sapper team arrived within 50 meters (54 yards) of the karst mountain peak at 1000 hours, March 10. By 1600 hours the team confirmed its plan. It was ready.

Linkages: Vietnam and Laos
US tackles the linkages
Challenges to Rolling Thunder pilots
TACAN at LS-85
TSQ-81 at LS-85: Process to make it happen
TSQ-81 at LS-85: Installation
TSQ-81 operations
Situation Assessment: Houaphanh Province
NVA plans attack
NVA moves to attack positions
US threat assessments - actions taken
The NVA attack
The aftermath