Outside of the combat base itself, there were several areas which were vital. The most critical points were the hill outposts, because both General Tompkins and Colonel Lownds were well aware of what had happened at Dien Bien Phu when the Viet Minh owned the mountains and the French owned the valley. It was essential that the hills around Khe Sanh remain in the hands of the Marines. Shortly after its arrival in mid-December 1967, 3/26 had relieved 1/26 of most of this responsibility. Company I, 3/26, along with a three-gun detachment of 105mm howitzers from Battery C, 1/13, was situated atop Hill 881S; Company K, 3/26, with two 4.2-inch mortars, was entrenched on Hill 861; and the 2d Platoon, A/1/26 defended the radio-relay site on Hill 950. This arrangement still left the NVA with an excellent avenue of approach through the Rao Quan Valley which runs between Hills 861 and 950. The regimental commander decided to plug that gap with the newly arrived 2d Battalion.(38)
At 1400 the day it arrived, Company F, 2/26, conducted a tactical march to Hill 558--a small knob which sat squarely in the middle of the northwestern approach. The rest of the battalion spent the night in an assembly area approximately 1,300 meters west of the airstrip. The following day, Lieutenant Colonel Heath moved his three remaining companies and the CP group overland to join Company F. Once the Marines were dug in, the perimeter completely encompassed Hill 558 and blocked enemy movement through the Rao Quan Valley.(39)
Even with 2/26 in position, there was still a flaw in the northern screen. The line of sight between K/3/26, on Hill 861, and 2/26 was masked by a ridgeline which extended from the summit of 861 to the northeast. This stretch of high ground prevented the two units from supporting each other by fire and created a corridor through which the North Vietnamese could maneuver to flank either Marine outpost. About a week after his arrival on Hill 558, Captain Earle G. Breeding was ordered to take his company, E/2/26, and occupy the finger at a point approximately 400-500 meters northeast of K/3/26. From this new vantage point, dubbed Hill 861A, Company E blocked the ridgeline and was in a good position to protect the flank of 2/26. Because of its proximity to K/3/26, Company E, 2/26, was later transferred to the operational control of the 3d Battalion. Although these units did not form one continuous defensive line, they did occupy the key terrain which overlooked the valley floor.(40)