In both the early and late October outpost battles the Chinese had attempted to seize critical terrain on the flanks of the 1st Marine Division. Although the majority of these attacks failed, the enemy had acquired six outposts early in the month--three in the western Korean Marine Corps sector and three north of the right regimental line. On the last day of October, two hours before midnight, the CCF again struck the Marine left flank. This time their efforts were directed against four outposts that screened Hill 155, the most prominent terrain feature in the entire KMC regimental zone. The fighting that developed was brief but very sharp and would be the most costly of all KMC clashes during this third winter of the war. The latest enemy attack came as no real surprise to Korean Marines of the 5th Battalion, occupying COPs 39, 33, and 31 in the northern regimental sector, or 2d Battalion personnel at COP 51 in the southern (western) half of the MLR. (Map 19.) The four outposts assisted in defense of the MLR (particularly Hill 155 just inside the MLR), afforded observation of CCF approach routes, and served as a base for friendly raids and offensive operations. Hill 155 overlooked both the wide Sachon Valley and Chinese frontline positions to the west. This critical Korean hill also commanded a view of the Panmunjom peace corridor, Freedom Gate Bridge, and the Marine division area east of Line JAMESTOWN in the KMC sector. Hill 155 had further tactical importance in that it protected the left flank of Paekhak Hill, the key ground in the entire 34-mile expanse of JAMESTOWN within 1st Marine Division territory. Actually, the probability of a determined enemy attack against the four outposts had been anticipated since early October following CCF seizure of three positions (former COPs 37, 36, and 86) in their strike against the KMC regimental OPLR. The enemy had then proceeded to organize an OPLR of his own with the two northern outposts, COPs 37 and 36, and informally occupied another position to the south and one toward the north in the vicinity of COP 39. “With this OPLR once firmly organized, the enemy will have an excellent jump-off point towards our OPs 39 and 33, his next probable objectives,” KMC officers reasoned.[297] [297] KMC Regt UnitRpt 216, dtd 4 Oct 52, p. 2. Sporadic probes throughout the month in the COP 39 and 33 areas indicated continued enemy interest in the positions. COP 51, to the south, was considered another likely target because of its location immediately east of COP 86, previously annexed by the CCF.