Battle of Lima Site 85 The Battle of Lima Site 85 was a Vietnam War attack by forces of the Vietnam People ' s Army on a clandestine United States base in the neutral Kingdom of Laos with airstrip , command post , helicopter landing zone , TACAN , and Commando Club radar . The attack included two artillery barrages , an infantry assault toward the sloped portion of Phou Pha Thi , and a raid on the mountaintop TACAN / radar area by commandos who scaled the mountain ' s cliff . Despite supporting airstrikes by the Seventh Air Force , the outnumbered Hmong " Secret Army " and Thai defenses were overwhelmed by the attack , the entire site was captured , and most of the US personnel were killed - including CMSgt Richard Etchberger who was awarded the Medal of Honor . The battle resulted in the largest single ground combat loss of United States Air Force members during the Vietnam War . Background . The Lima Site 85 U . S . military installation began with a CIA airstrip and command bunker for supporting local forces in the Laotian Civil War against North Vietnamese and Pathet Lao forces of the North Military Region . The USAF subsequently added tactical air navigation system ( TACAN ) equipment to the mountaintop and a helicopter landing zone ( LZ ) below the summit in August 1966 to support flights into northern areas . By November 1 , 1967 , to provide a Combat Skyspot ground - directed bombing capability against northern North Vietnam targets particularly for the monsoon season , a Reeves AN / TSQ - 81 Bomb Directing Central and other structures were added near the TACAN . The central directed aerial bombing and was operated by two 5 - man crews on day / night shifts with weekly rotations ( TACAN Circuit Rider personnel of the 1st Mobile Communications Group and the CIA case officer were also rotated . ) Prior to emplacement of the AN / TSQ - 81 , the 7th Air Force estimated the enemy would attack the site about 6 months after radar operations began . The radar crews were manned with military volunteers discharged from the USAF so their civilian status would provide cover if they were identified operating in the neutral Kingdom of Laos . Defenses . Hmong defenders at LS - 85 included 200 soldiers guarding the ridge and 800 in the valley . Defense of the perimeter with diameter also included " 1 company ( about 100 men ) of Thai infantry " . A Hmong 105 mm howitzer was emplaced at LS - 85 , and the mountaintop personnel were eventually supplied with small arms : 10 M16 rifle s , sidearms , ammunition , fragmentation grenade s , and concussion grenade s . A January 25 exercise was conducted for delivering airstrikes to the site for protection prior to and during the evacuation , and by February an evacuation plan was in place for the mountaintop personnel . To remove the risk of detonation , the U . S . technicians removed demolition charges from the mountaintop structures and threw them over the cliff . Similar North Vietnamese / Pathet Lao offenses against sites in Laos began at the end of 1967 such as the 15 December attack against Nam Bac , the stronghold of the Royal Laos Army . On 16 December east of Phou Pha Thi , 2 Pathet Lao companies overran Phou Den Din which was recaptured shortly afterward . Douglas A - 26 Invader s attacked forces on Route 6 and Route 19 at night , and Nam Bac was captured on 14 January 1968 . Preceding engagements . In addition to Buddhist monks with cameras presumed to be enemy agents who tried to gain access to the summit , a 5 - man enemy patrol was dispersed from the base of the mountain on January 10 , and on January 30 " enemy troops detonated some of the defensive mines . . . and brought the ridgeline under mortar fire " . On 18 February 1968 , a North Vietnamese artillery survey team was ambushed near Lima Site 85 by Hmong reconnaissance teams , killing a North Vietnamese major with a notebook that identified the plan to attack Phou Pha Thi with 4 battalions . As a diversion for the attack on LS - 85 , the North Vietnamese made movements against Muong - son . An - 2 airstrike . On 12 January , 4 Antonov An - 2 biplanes flew towards Lima Site 85 , and 2 dropped 120 mm mortar shells through the fuselage floors and strafed with 57 mm rockets from the wing pods . A Bell UH - 1D Air America helicopter piloted by Theodore Moore successively pulled alongside each An - 2 and Glenn Woods downed the biplanes with AK - 47 fire . The 2 remaining An - 2 observing from a distance escaped without damage . The attack killed 2 Hmong men and 2 women , but the TSQ - 81 radar and all associated equipment were not damaged . The wreckage of an An - 2 biplane was displayed at the That Luang Monument as evidence of North Vietnamese activities in the country . After the attacks , the USAF officer at Udorn RTAFB responsible for LS - 85 security , Major Richard Secord , armed the radar technicians at LS - 85 . Battle of Route 602 . The Battle of Route 602 was a 1968 US aerial bombing campaign against a ~ Laos road being constructed through the jungle from Sam Neua for bringing North Vietnamese artillery to attack Lima Site 85 . To " prevent the completion of the road " ( US designation " Route 602 " ) the Seventh Air Force " launched 165 tactical air sortie s during January " including " 45 sorties on 3 January 1968 " and diverted 7th Air Force aircraft attacking nearby on January 25 . The Joint Chiefs of Staff " urgently " requested " increased air support " on February 20 , and on " 21 February the Ambassador authorized the Local Area Defense Commander ( alternately the senior CIA officer or the FAC ) to use the TSQ radar to direct any and all strikes within 12 kilometers of the summit " ( " from 20 – 29 February , 342 strike sorties hit within 30km of Site ' 85 " . ) Commando Club operations against Route 602 and advancing troops were part of the approximately 400 Commando Club missions out of the " 1 , 472 BARREL ROLL Strike missions " flown " around " LS - 85 from November 1 - March 10 . The bombing campaign failed to prevent the enemy from reaching positions near LS - 85 for which the order from Washington , D . C . , was then to " " hold the site at all costs . " Plans and preparations . The VPA plan to capture LS - 85 included the use of a Special Forces element against the mountaintop installation . Assault Element 1 underwent 9 months of specialized training including physical conditioning , mountaintop combat , mountain climbing , and jungle operations . Afterward , soldiers of the VPA 41st Special Forces Battalion conducted terrain reconnaissance and watching activities on Lima Site 85 beginning 18 December 1967 . On 22 January 1968 , six North Vietnamese sappers were sent out to climb Phou Pha Thi for identifying LS - 85 positions and routes of withdrawal . On 28 February 1968 , the North Vietnamese Special Forces completed their preparations and began marching towards their assembly point on 1 March . For secrecy , the en route Assault Elements avoided contact with local civilians and opposing military forces and were to engage opposition using small forces while the main formation continued to the assembly area . Shortly after arriving at the assembly point , the Special Forces test fired their weapons at an undisclosed location for two days . On 9 March , the elements arrived in the vicinity of Phou Pha Thi , with their attack to commence during the early hours of 9 or 10 March . Assault Element 1 had 5 cells with Cells 1 & 2 to capture the communications center . Cell 2 ' s secondary role was to support Cell 3 , which was to seize the TACAN site and eliminate all U . S . personnel . Cell 4 was ordered to capture the airstrip , and Cell 5 was placed in reserve to support other units . Evacuation planning . The VPA Regiment had penetrated within of Phou Pha Thi by February 25 , after which the US Ambassador to Laos , William H . Sullivan , reported " it seems doubtful that the site can be held in the face of consistent enemy determination " . On March 9 , CINCPACAF notified the 7 Air Force / 13 Air Force deputy commander he was " approved " to " direct evacuation of site and destruction of equipment " under approved OPlan 439 - 68 . LS - 85 was surrounded by March 9 with 4 battalions of the VPA 766th Regiment — including 1 Pathet Lao battalion — totaling more than 3 , 000 men . On March 10 when the AN / TSQ - 81 day shift crew ( 6am - 6pm ) completed duty , Lt Col Clarence F . Blanton held a meeting with both crews at which they agreed to direct bombings against the night ' s targets and evacuate the next day . Around 8 : 20pm during the battle the U . S . Ambassador authorized airstrikes against the VPA regiment on the lower slopes of the mountain and , at 9 : 15pm after artillery fire commenced , had started considering evacuating all U . S . personnel at first light ( the 7 / 13AF deputy commander indicated " evacuation should be commenced only as a last resort if the situation became untenable . " ) After artillery fire resumed the evening of March 10 , Sullivan ordered 16 of the 19 US personnel be evacuated by 8 : 15am the next morning . At 5 : 15am unaware of the mountaintop raid , Sullivan authorized the evacuation to start at 7 : 15am . Battle . The attack on Phou Pha Thi began about 6 : 00pm on 10 March with an artillery barrage while a Special Forces team climbed " up the mountain to dismantle the mines and quick - fuse grenades " on infiltration routes . At 7 : 45pm the barrage stopped having disabled the Hmong 105 mm howitzer with a direct hit . At 8 : 21pm the artillery attack resumed until about 9 : 00pm followed by several infantry assaults by the VPA Regiment . About 3 : 00am , Assault Team 1 Cell 4 maneuvered to the airstrip ' s west side ( instead of the planned east side ) to use the higher terrain and buildings . Their attempt to seize the airstrip was blocked by a Hmong mortar position . The Cell 4 commander was isolated from his three soldiers , and the cell fought to hold positions until daybreak against an encirclement by about 2 Hmong platoons . Cell 4 escaped by using the rough terrain to cover their positions and later linked up with other units at the mountaintop . " About four in the morning " , the 7th Air Force began an aerial counterattack to defend LS - 85 , causing the hill facing Phou Pha Thi and most of the valley between ( to the northeast ) to be " set ablaze or obscured by smoke " ( Capt Donald Westbrook was shot down in his Douglas A - 1 Skyraider and died . ) An Air America helicopter landed on the airstrip and picked up 2 CIA officers and 1 forward air - controller . The VPA captured one 105 mm howitzer , one 85 mm artillery piece , four recoilless rifles , four heavy mortars , nine heavy machine guns and vast amounts of ammunition . Mountaintop raid . As the radar crews ' meeting was ending regarding the mountaintop evacuation , the initial artillery barrage struck the defensive bunker ( AN / TSQ - 81 antenna cabling was also damaged . ) About 8 : 40 pm , the Special Forces had climbed to the mountaintop and after midnight communication was cut between the helipad and the mountaintop . At 3 : 45am Cell 1 moved to within of the communications center , where a Hmong guard at an outpost threw a hand grenade at Cell 1 but missed . Cell 1 defeated the post with a grenade and then destroyed the " building that had many antennas " with an RPG . After the RPG exploded , Cell 3 destroyed the electrical generators with an RPG and " after only 15 minutes , Cells 1 and 2 [ had ] seized the American communications site . The CIA case officer , Evan Washburn , at the airstrip reported the mountaintop gunfire to Secord at Udorn RTAFB . Hearing explosions , 2 U . S . technicians and Lt Col Blanton were killed rushing out of the operations shelter . For a defensive shelter , 3 of the day shift radar personnel joined 2 others who had been sleeping in a small cave at the west cliff and listened until the initial assault ended . When a cell investigated near the cliff , Captain Sliz directed SMSgt Etchberger to fire and the enemy counterfire killed Hank Gish ( wounded Sliz used the corpse as a shield when he jumped on a grenade ) . At 4 : 15am , in response to the gunfire from the U . S . technicians , the assault team commander ordered Cell 5 to reinforce Cell 3 , and they captured the mountaintop at 4 : 30am . Below the installation at the cave with 3 other survivors , Sliz was notified by a C - 130 flare ship that help was en route . About 6 : 00am from the airstrip the CIA case officer lead a Hmong squad that counterattacked the mountaintop forces and then retreated and unsuccessfully counterattacked again at 6 : 15 to retreat at 6 : 25am under fire from Cells 1 and 2 guarding the communication site . After repelling the counterattack , Cell 2 was ordered to support Cells 3 and 5 in their fight at the main TACAN installation . By 6 : 35am , Cells 2 & 5 had " killed nearly all the enemy who still survived , broke up the enemy attacks , and took firm control of the TACAN station . " Capt Sliz at the cave directed a counterstrike by U . S . aircraft that strafed and bombed the mountaintop with 20 mm cannon and cluster bombs . The unrecovered 11 U . S . personnel were subsequently listed missing in action , 1 of 4 cave survivors was killed ( Etchberger ) during the evacuation at daylight , and an additional technician who had played dead on the mountaintop ran to be evacuated with them . Later during the day , reconnaissance was able to " recover or account for eight " of the dead U . S . LS - 85 personnel and a number of wounded Hmong soldiers . In " late morning on 11 March , airstrikes were directed against the summit " , and from midday all areas of Lima Site 85 were held by the VPA 41st Special Forces Battalion until it withdrew on 14 March . Aftermath . With " encryption devices , codes , and software " left behind , 95 USAF airstrikes were used March 12 – 18 to destroy the mountaintop facilities ( the last attack by Bill Plank in a Douglas A - 1 Skyraider completed the task . ) On July 18 , Hmong commandos " reach [ ed ] the destroyed helipad and TSQ facility but were unable to hold the ridgeline [ against the ] 148th NVA Regiment " . The Hmong Operation Pig Fat on November 1 to retake Phou Pha Thi was defeated . The 11 U . S . MIA were later designated KIA / body not recovered , and between 1994 and 2004 , 11 investigations were conducted by both Joint POW / MIA Accounting Command ( JPAC ) and unilaterally by Lao and Vietnamese investigators on both sides of the border . An NVA soldier ' s recollections of the attack were documented in 1996 . In 2002 former VPA soldiers of the raid said they had thrown bodies off the mountain and March 2003 videotape of dummies thrown from the cliff allowed recovery from a ledge below of boots in four sizes , five survival vests , and other fragments of material . By 7 December 2005 TSgt . Patrick L . Shannon ' s remains had been identified , on 14 February 2007 the remains of Capt Donald Westbrook were identified , and on July 16 , 2012 , the remains of Lt Col Blanton were identified . Names of the LS - 85 personnel killed were included on the Combat Skyspot Memorial on Andersen Air Force Base , Guam ( its AN / MSQ - 77 antenna was destroyed by a typhoon ) .