The "Green Berets" were the first American troops in the area when, in August 1962, they established a Civilian Irregular Defense Group (CIDG) at the same site which later became the Khe Sanh Combat Base (KSCB). The first Marine unit of any size to visit the area was the 1st Battalion, 1st Marines (1/1) which, in April 1966, was participating in Operation VIRGINIA. In early October 1966, the 1st Battalion, 3d Marines, which was taking part in Operation PRAIRIE, moved into the base and the CIDG camp was relocated near Lang Vei, 9,000 meters to the southwest where it continued surveillance and counterinfiltration operations. The battalion remained at Khe Sanh with no significant contacts until February 1967 when it was replaced by a single company, E/2/9.[2] In mid-March 1967, Company E became engaged in a heavy action near Hill 861 and Company B, 1/9 moved in to reinforce. After a successful conclusion of the operation, E/2/9 returned to Phu Bai, and B/1/9 remained as the resident defense company.
The KSCB sat atop a plateau in the shadow of Dong Tri Mountain and overlooked a tributary of the Quang Tri River. The base had a small dirt airstrip, which had been surfaced by a U. S. Navy Mobile Construction Battalion (Seabees) in the summer of 1966; the field could accommodate helicopters and fixed-wing transport aircraft. Organic artillery support was provided by Battery F, 2/12 (105mm), reinforced by two 155mm howitzers and two 4.2-inch mortars. The Khe Sanh area of operations was also within range of the 175mm guns of the U. S. Army's 2d Battalion, 94th Artillery at Camp Carroll and the Rockpile. In addition to B/1/9 and the CIDG, there was a Marine Combined Action Company (CAC) and a Regional Forces company located in the village of Khe Sanh, approximately 3,500 meters south of the base.[3]
All these units sat astride the northwest-southeast axis of Route 9 and had the mission of denying the NVA a year-round route into eastern Quang Tri Province. The garrison at Khe Sanh and the adjacent outposts commanded the approaches from the west which led to Dong Ha and Quang Tri City. Had this strategic plateau not been in the hands of the Americans, the North Vietnamese would have had an unobstructed invasion route into the two northern provinces and could have outflanked the Allied forces holding the line south of the DMZ. At that time, the Americans did not possess the helicopter resources, troop strength, or logistical bases in this northern area to adopt a completely mobile type of defense. Therefore, the troops at the KSCB maintained a relatively static defense with emphasis on patrolling, artillery and air interdiction, and occasional reconnaissance in force operations to stifle infiltration through the Khe Sanh Plateau. In the event a major enemy threat developed, General Walt could rapidly reinforce the combat base by air.(7)