During the remainder of 1966 and in the first quarter of 1967, the intensity of fighting in the eastern DMZ area increased. Each time the enemy troops made a foray across the DMZ, the Marines met and defeated them. By 31 March 1967, the NVA had lost 3,492 confirmed killed in action (KIA) in the northern operations while the Marines had suffered 541 killed. For the Communists, it appeared that direct assaults across the DMZ were proving too costly--even by their standards.[(5)]
The Khe Sanh Plateau, in western Quang Tri Province, provided the NVA with an excellent alternative. The late Doctor Bernard B. Fall compared the whole of Vietnam to "two rice baskets on opposite ends of a carrying pole." Such being the case, Khe Sanh is located at the pole's fulcrum in the heart of the rugged Annamite Range. Studded with piedmont-type hills, this area provides a natural infiltration route. Most of the mountain trails are hidden by tree canopies up to 60 feet in height, dense elephant grass, and bamboo thickets. Concealment from reconnaissance aircraft is good, and the heavy jungle under-growth limits ground observation to five meters in most places. Dong Tri Mountain (1,015 meters high), the highest peak in the region, along with Hill 861 and Hills 881 North and South dominate the two main avenues of approach.[1] One of these, the western access, runs along Route 9 from the Laotian border, through the village of Lang Vei to Khe Sanh. The other is a small valley to the northwest, formed by the Rao Quan River, which runs between Dong Tri Mountain and Hill 861. (See [Map 3]). Another key terrain feature is Hill 558 which is located squarely in the center of the northwestern approach. The only stumbling block to the NVA in early 1967 was a handful of Marines, U. S. Army Special Forces advisors, and South Vietnamese irregulars.[(6)] (See [Map 3]).
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)]
On 20 April 1967, the combat assets at KSCB were passed to the operational control of the 3d Marines which had just commenced Operation PRAIRIE IV. The Khe Sanh area of operations was not included as a part of PRAIRIE IV but was the responsibility of the 3d Marines since that regiment was in the best position to oversee the base and reinforce if the need arose. The need arose very soon.[(8)]
On 24 April 1967, a patrol from Company B, 1/9 became heavily engaged with an enemy force of unknown size north of Hill 861 and in the process prematurely triggered an elaborate North Vietnamese offensive designed to overrun Khe Sanh. What later became known as the "Hill Fights" had begun. In retrospect, it appears that the drive toward Khe Sanh was but one prong of the enemy's winter-spring offensive, the ultimate objective of which was the capture of Dong Ha, Quang Tri City, and eventually, Hue-Phu Bai.[4] That portion of the enemy plan which pertained to Khe Sanh involved the isolation of the base by artillery attacks on the Marine fire support bases in the eastern DMZ area (e.g., Camp Carroll, Con Thien, Gio Linh, etc.). These were closely coordinated with attacks by fire on the logistical and helicopter installations at Dong Ha and Phu Bai. Demolition teams cut Route 9 between Khe Sanh and Cam Lo to prevent overland reinforcement and, later, a secondary attack was launched against the camp at Lang Vei, which was manned by Vietnamese CIDG personnel and U. S. Army Special Forces advisors. Under cover of heavy fog and low overcast which shrouded Khe Sanh for several weeks, the North Vietnamese moved a regiment into the Hill 881/861 complex and constructed a maze of heavily reinforced bunkers and gun positions from which they intended to provide direct fire against the KSCB in support of their assault troops. All of these efforts were ancillary to the main thrust--a regimental-sized ground attack--from the 325C NVA Division which would sweep in from the west and seize the airfield.[5] [(9)] (See [Map 4]).