E. WILSON
1st MARINE DIVISION
POST-ARMISTICE MAIN BATTLE POSITION
30 SEPTEMBER 1953
Marine support units—motor transport, tank, service, medical, aerial liaison (VMO/HMR)—were in the same general rear area, as was the headquarters of the U.S. 25th Infantry Division. The Marine Division CP continued to be located at Yongji-ri, although construction of a new site further south at Chormyon was due to be completed by engineer personnel on 1 October. The division railhead and truckhead remained, respectively, at Munsan-ni and Ascom City. To the left of the KMC sector was the 1st Amphibian Tractor Battalion. Still further west, separated from other units by the Han River, was the Kimpo Provisional Regiment, in its former wartime sector.
As the division OPLR regiment, the 5th Marines held a line 36,000 yards in length—about 21 miles—roughly corresponding to the front manned by three regiments during the war. The OPLR sector included the entire area in the divisional zone of responsibility north of the Imjin. Boundaries of the 5th Marines territory were the southern DMZ truce line on the west and north, the Samichon River to the east, and that major water barrier, the curving Imjin River, to the rear.
After establishment of the DMZ, the division occupied unfavorable low ground poorly suited to the defense and inferior to that held by the enemy—continuing the same situation that had existed during the period of stabilized combat operations in West Korea. Almost without exception the southern boundary of the DMZ prohibited the Marines from moving onto the commanding terrain, as the No-Pass Line was behind or along the reverse slopes of the high ground. On the other hand, in most cases the CCF had the advantage of having forward slope positions as well as the crests plus most of the commanding terrain in the area.
Communist territory in the northern DMZ sector included the former strongholds of Yoke, Bunker Hill, Carson, Reno, Vegas, Berlin, East Berlin and Warsaw. Within the Marine division postwar area were the Panmunjom Corridor and outposts Marilyn, Kate, the Boulder City hills, and the Hook. Much of the terrain between the major hill positions along the 5th Marines regimental front and the Imjin River consisted of low-rolling hills rising abruptly out of the rice paddies.
Construction of new positions and the defense system of the 5th Marines was based on several assumptions about enemy capabilities, made by G-2 and the new regimental CO, Colonel Rathvon McC. Tompkins, who had assumed command on 2 August. These were: that in the event of resumption of hostilities by the CCF the enemy would use his jet fighters and bombers in support of operations; that he would continue to have numerical superiority in artillery; and that the northern outpost regiment would have no reinforcement or surface resupply from units south of the Imjin.
The defense plan for the forward part of the 5th Marines sector in event of a resumption of hostilities called for furnishing patrols equipped with radios and FO teams to occupy Hills 155, 229, and 181. (Hill 155 was directly south of the DMZ in the 2/5 left battalion sector; Hills 229 and 181 were, respectively, just inside and just outside the southern boundary of the truce line in the center 1/5 sector.) From these three elevations the patrols would then have the mission of bringing down artillery fire on enemy concentrations and relaying communications about the situation to the friendly main attack force. Other critical hill masses in the OPLR regimental sector were Hill 126 (in the 3/5 eastern battalion sector, just inside the Marine side of the DMZ) and Hill 163, in the Hook area. The latter hill was not as suitable for defense since it was located south of the military demarcation line and was thus less accessible.