Another difficulty was the inadequate allocation of ammunition: one-half JAMESTOWN load on position, and another half-load available at the regimental dump. The JAMESTOWN load unit had been developed for use in a stabilized defense situation where automatic weapons were aimed as the enemy came in close proximity to the MLR. On the other hand, OPLR machine guns and weapons were required to open up at maximum ranges and might well be fired for extended periods of time. It was calculated that A4 machine guns firing at medium rate (75 rpm) would expend the one-half JAMESTOWN load in 22 minutes, while an A1 machine gun at medium rate (125 rpm) would exhaust the same load in 13 minutes. A partial improvement was obtained by moving the ammunition loads from regimental to battalion dumps although the basic problem of limited allocation—shared also by rear infantry regiments—continued to exist.
An unique situation that had confronted the 2d Battalion and at times the adjoining 1st Battalion stemmed from the large numbers of Army engineer personnel building the nonrepatriate POW camp in the DMZ immediately west of the 2/5 sector. During August and the first part of September, the area in front of 2/5 had been used as a base camp for 5,000–7,000 construction personnel. Although their area was crowded with these additional units, the Marine battalions could not exercise any control over them. The Marines were still responsible for security of the sector, however. Presence of as many as 22,000 nonrepatriate CCF and NKPA prisoners as well as the Indian custodial forces further complicated the matter. It was noted that:
At the same time the Army engineers were building the camp, the prisoners were situated in the middle of the 2/5 area and the MSR to Panmunjom led completely across the battalion position into the 1/5 sector [and thence] into the DMZ. Upon completion of the camp, the engineers withdrew from the area but as they withdrew the 5,500 troops of the Custodial Forces India were brought in to guard the nonrepatriate prisoners. With the arrival of the prisoners, the number of personnel in the regiment’s sector of responsibility rose to 28,000–30,000. Thus, the problem of having a GOP mission and at the same time having never less than 5,000 and as many as 30,000 friendly, neutral, and/or prisoner personnel in front of our most forward defended localities was always present.[678]
[678] 5thMar Hist, pp. 6–7, Folder #3.
Camp construction and development of the new positions south of the river continued at a furious pace from August through early October. Since the new camp sites were in civilian populated areas, “it was necessary to secure real estate clearance before they could be occupied or improved.”[679] After clearance was obtained on 29 July, division engineers immediately began work on five separate camps. These camp building activities and reconnaissance of assigned blocking positions continued until 10 August. At this time, construction began on the major blocking positions, so organized and developed as to be self-sustaining for several days. Whether squad, platoon, or company, all positions were organized using a perimeter type defense and were mutually supporting laterally and in depth. Connecting trenches, bunkers, ammunition holes, and tank slots were also built.
[679] 1st EngrBn Rpt, Operations during 27 Jul-31 Oct 53, dtd 19 Apr 53, p. 4, Folder #6.
By early October, construction of the blocking positions was completed by the 1st Marines despite the fierce summer heat, the numerous rock formations in the area that were difficult to dig out with limited tools and demolitions, and the shortage of personnel due to units participating in the new series of division MARLEX exercises, resumed in October. Within three months, the Marine division had thus largely completed building of a solid defense in its new main battle position. The importance of maintaining combat readiness for any renewed hostility on the part of the enemy demanded continuing vigilance at all times.
Defense specifications throughout the 5th Marines northern general outpost sector called for some 1,560 individual fighting positions, 400 automatic weapons sites, 8 bunkered infantry OPs, 30 bunkered CPs, 15,400 yards of trenchlines, and 70,000 yards of protective and tactical wire. In construction of the MBP, all bunkers were so blended and camouflaged with the natural terrain that they were almost impossible to be seen.
To the division rear, the location of recoilless rifle positions, FDC bunkers, and tank slots in the blocking positions and bridgeheads was the major priority. In the antimechanized defense plan, tanks covered likely avenues of approach into the general outpost area and also overlooked critical river crossing sites. Wherever possible old firing positions which had been previously prepared to support the secondary lines WYOMING and KANSAS were utilized. By the end of the year, 204 tank firing positions had been emplaced throughout the Marine division sector.
Three rehearsals for the occupation of the main battle position were held by the 1st Marine Division in September. All division units, both combat and service, participated in these exercises. Tactical units were required to occupy the MBP and be fully prepared for combat on four hours’ notice; service units were to provide additional local security required for the elimination of enemy infiltrators or guerrilla agents. Divisional and I Corps test exercises indicated that three hours were necessary to man the MBP during daylight and approximately three and one half hours at night.