[421] Unless otherwise noted, the material in this section is derived from: _PacFlt Eval Rpts_ No. 5. Chap 6, No. 6, Chaps. 7, 9; 1stMarDiv ComdDs, May-June 53; 1stMarDiv G-3 Jnls, 22 Apr-30 Jun 53; 1stMar, 5thMar, 7thMar, 11thMar, 1st EngrBn, HMR-161, VMO-6 ComdDs, May-June 53; Field, _NavOps, Korea_. While the division was in reserve, its tactical mission consisted of preparation for commitment on I Corps order as a counterattack force in any of the four division sectors of I Corps. Division Operation Plan 7-53 implemented this I Corps Plan “RESTORE” and set forth the designated blocking positions in the 25th Army, Commonwealth, 1st ROK, and 7th Army Division sectors in event of threatened or actual enemy penetration of the MLR. The 1st Marine Division’s Training Order 8-53, issued on 6 May, the day after the relief was officially effected, outlined the training to be accomplished during the eight-week reserve period, 10 May-5 July. Following a few days’ interval devoted to camp construction and improvement of facilities, an active training program commenced. Its objective was the continued improvement of amphibious and ground offensive combat potential of all personnel. Three major regimental combat team MARLEXES were scheduled.[422] The training syllabus called for a four-phased progressive schooling from individual to battalion and regimental level conducted in all phases of offensive, defensive, and amphibious warfare. Weaponry familiarization, small unit tactics, and combined unit training, with tank-infantry deployment and integration of helicopters at company-level exercises, were emphasized, culminating in a week-long field maneuver. [422] Relief from the Eighth Army defense line provided the first opportunity for expansion of the 1st Marine Division amphibious training to regimental level. Amphibious training in battalion-sized MARLEXES had been under way since June 1952, upon transfer of the Marines to the western coastal sector. This had, in fact, “produced an extra dividend as [their] amphibious retraining program, conducted throughout the summer in the Tokchok Islands, was apprehensively observed by the enemy.” Field, _NavOps, Korea_, p. 430. Lectures were to be kept to a minimum, with at least 50 percent of the tactical training conducted at night. Specialty training in intelligence, signal communications, antitank and mortar, machine gun, mine warfare, and staff NCO schools was also prescribed. Numerous command post exercises were programmed to obtain a high standard of efficiency in both battalion and regimental-level staff functioning. It was the first time the division had been in reserve since a brief two-week period in late July-August of 1951. A brisk 40–44 hour week, plus organized athletics, insured that the training period was to be fully utilized.