Lima Site 85 (LS-85 alphanumeric code of the phonetic 1st letter used to conceal this covert operation[3]) was a clandestine military installation in the Royal Kingdom of Laos guarded by the Hmong "Secret Army", the Central Intelligence Agency, and the United States Air Force used for Vietnam War covert operations against communist targets in ostensibly neutral Laos under attack by the Vietnam People's Army.

[4] LS-85 was supplied via an "Air America STOL airstrip[5] … two-thirds of the way down the mountain"[6] and the command bunker was down the hill from the summit[2] (identified by the North Vietnamese as the "communications center".

[5]: 1  The planned LS-85 TACAN site was surveyed in July 1966 (the Hmong flattened the summit and created a helicopter landing zone at lower elevation).

[12] The site was developed under USAF Major Richard Secord (assisted by [specify]Tom Clines) by first "clearing additional space on the white karst limestone mountaintop"[6] with blasting by a "Navy Seabee demolitions expert".

[18]: 36  Construction included leveling steel girders on vertical posts to allow a Corps of Engineers[19] CH-47s to airlift[20] the "new equipment, vans [rigid shelters], and prefab crew quarters".

The Detachment 1, 1043rd Radar Evaluation Squadron, technicians and officers at LS-85[23] performed radar/computer/communications operations with the Reeves AN/TSQ-81 Bomb Directing Central as Lockheed civilians (volunteers discharged from the USAF for cover).

The central at LS-85 automatically effected release of the ordnance from the aircraft to eliminate the variable crewmember delay during the greater vulnerability of the generally steady bomb run.

The LS-85 radar using day/night shift crews of 5 men each[4] became operational on November 1, 1967;[14] and trial missions[clarification needed] of Commando Club by Republic F-105 Thunderchiefs were led[specify] by Col. John C. Giraudo[9] (355th Fighter Wing commander).

[9] The latter mission's loss of 2 Wild Weasels to MiGs and then some of the bombers to SAM sites that tracked the USAF jamming resulted in temporary suspension of Commando Club until electronic countermeasures were improved.

"[6] The initial assessment by the site's 7th AF coordinator was that after radar operations began LS-85 would be attacked within 6 months,[18]: 35  which a February 25 CIA report accurately predicted would be after March 10.

* The May 11, 1997, DoD translation of Do Chi Ben's Tran Tap Kich Vao Khu 'TACAN' tren Nui Pa-thi cuar Phan doi Dac Cong Quan Khu, ngay 11 thang 3 nam 1968 by Robert J. Destatte (translation edited April 7, 1998) is entitled Raid on the TACAN Site Atop Pha-Thi Mountain by a Military Region Sapper Team on 11 March 1968.