The base was subsequently hit by a mortar barrage on January 30, then on February 18 Hmong militia ambushed and killed a team of NVA artillery observers near the mountain and recovered plans for a coordinated bombardment of the facility. American military leaders knew the isolated base was surrounded by stronger enemy forces and likely to come under attack, but the base’s TACAN support was considered so valuable that Amb. William Sullivan resisted evacuating the site. Unable to deploy significant defenses, the base’s technicians instead began dispatching hundreds of airstrikes against nearby communist forces to secure their position. Elite North Vietnamese commandos from the 41st Special Forces battalion had already scaled the seemingly impassible cliffs on Phou Pha Thi’s northside without being detected on January 22 and reconnoitered the most feasible infiltration routes. Early that March, a thirty-three man platoon under the command of Lt. Truong Muoc assembled near the mountain, where they were reinforced by a nine-man sapper squad. The commandos were equipped with AK-47s, SKS carbines, explosives, hand grenades and three rocket-propelled grenade launchers. At 6PM on March 11 an artillery bombardment gave cover for Truong’s pathfinders to clear out mines and secure the infiltration paths to Lima 85. A few hours later, regular troops of the 766th Regiment of the NVA and a Pathet Lao battalions launched an attack that pinned down the Hmong troops in the valley around the mountain. Finally around 9 PM, Truong’s men began scaling up the cliff, the operators splitting into five “cells” to launch a multiprong attack. Cells One and two would concentrate on the command post, cells three and four would seize the TACAN equipment and airstrip respectively, and the fifth cell would remain in reserve. The base personnel reported the artillery bombardment, but Ambassador Sullivan decided not to order an evacuation unless the attack proved to be overwhelming. Only by 8 AM the following morning did he dispatch helicopters and air support to cover the personnel’s escape.
Sébastien Roblin holds a master’s degree in conflict resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring.