Original Vietnam War military topographic map titled Lien Thach measures 29 x 22.5 inches (74 x 59 cm) and covers jungle terrain in central Phu Yen Province, with parts of Tuy Hoa Province included. 

Printed in 1966 by the U.S. Army Map Service as part of the standard 1:50,000 series used for field operations. Identified by its detailed terrain contours, grid system, and bilingual labeling, the map documents the heart of jungle warfare zones near and south of the Song Da Rang (River), and shows Highway 436.

The region shown was home to multiple U.S. Special Forces outposts, including the Lien Thach base, which served as a launch point for reconnaissance patrols, Civilian Irregular Defense Group (CIDG) support, and interdiction missions against Viet Cong and PAVN activity along river valleys and mountain trails. 

The dense terrain in this section of Phu Yen made it ideal for enemy movement and concealment, and it became a contested corridor used by VC units moving between coastal and highland positions. 

The PAVN often used the Song Da Rang as a transit route, and the surrounds served as bases for mortar and ambush attacks. U.S. Special Forces Recon Teams operated from Lien Thach to train local Montagnard militias, run civic action programs, and gather intelligence on enemy logistics and infiltration patterns.

The map was designed and printed for use by personnel assigned to MACV-SOG teams and other reconnaissance or special operations units. 

This zone was considered a high-risk area, where jungle canopy often restricted aerial visibility and necessitated ground patrols supported by helicopter insertions, forward observation, and artillery support coordinated from Tuy Hoa Air Base to the east. 

Tuy Hoa City / Air Base, although not shown on this sheet, was a major tactical air support base used for air strikes, medevac, and transport missions. 

American forces frequently launched air missions from Tuy Hoa and Pleiku into this region to disrupt VC jungle sanctuaries and trail networks.

From the communist perspective, the NLF and PAVN used this region as a lateral movement area to bypass more heavily monitored coastal zones. Their control was never static but rather fluctuated based on U.S. sweeps, weather, and local resistance. Ambushes, trail mines, and fortified jungle camps made it a deadly zone for Allied patrols. 

Intelligence gathered from this map and others like it helped guide long-range reconnaissance patrols (LRRPs), aerial surveillance, and village pacification programs.