The same tactics and techniques should not be followed in every raid. The pattern should be altered to the extent that the tactics and techniques employed will not indicate the objective to the enemy. The time selected for raids should vary to permit the conduct of both daylight and night raids. Employment of supporting arms including the delivery of smoke must be varied to prevent indication of the objective.[773]

[773] Lessons Learned 5-53, p. 2.

Enemy ability to locate listening posts and take them under direct fire or mortar attack also dictated the need for frequent change in location.

Regarding the use of supporting arms, the Korean terrain itself dictated a need for modification of traditional practices of employing both direct and indirect fire weapons in order to achieve maximum effectiveness. Standard Marine Corps use of both crew-served infantry weapons and artillery centered around the concept of interlocking and mutually reinforcing bands of fire. Neither the frontage nor terrain in Korea was what could be termed “normal.” Battalion frontages were often more than twice the accepted maximum. The terrain consisted of steep main ridge lines with many steep finger ridges leading off both sides. Such contours require twice as many machine guns for adequate defense against enemy attacks if employed in positions affording the usual interlocking grazing fire.

For both infantry weapons on the forward COPs and MLR, and supporting artillery batteries, the combination of “stretching unit fronts and unstretchable ranges”[774] of the weapons caused them to lose a considerable amount of their mutual support capability, as one artillery regimental commander commented about the experience of the 1st Marine Division in Korea. As a result, a compromise was often effected whereby machine guns were emplaced on the high ground of the ridge line, with their individual sectors of fire extended to 180 degrees. Although the guns were no longer mutually supporting, the numerous finger ridges could be better covered by fire to prevent the enemy from gaining a foothold on them prior to assault on the main ridge line.

[774] Col F. P. Henderson, “Amphibious Artillery of the Future,” Marine Corps Gazette, v. 39, no. 12 (Dec 55), p. 30.

As previously noted, the Marine division also modified its concept about occupying the military crest, rather than the topographical crest, of forward slopes.[775] In view of CCF tactics, forward slope positions offered the advantage of observation and superior fields of fire and assisted in bringing fire on the enemy in those areas and approaches masked from the view of reverse slope positions.

[775] See [Chapter VI].

Under conditions of stabilized defensive lines in Korea, the great offensive power of Marine tanks was somewhat limited. They were used extensively as direct fire weapons and supplemented the artillery regiment by firing deep H&I (harassing and interdiction) missions. In West Korea, it proved expedient to have friendly tanks positioned in defiladed assembly areas where they were on call and ready to move into MLR firing slots on short notice. They often provided close fire support to Marine patrols and outpost defense actions, sometimes being called in for fire missions before the direct support artillery.

Since tanks under enemy observation invariably drew retaliatory fire, they usually remained in firing positions on the MLR only long enough to complete their fire mission. Deployment of several M-46s in mutually supporting MLR positions, however, tended to reduce the volume of hostile fire. When operating forward of the MLR, it was important that the armored vehicles be protected by infantry from enemy tank-killer teams. Often the Marine artillery observer’s knowledge of the terrain and familiarity with objective targets upon which the tank could be effectively used was thus relayed to the tanker, particularly when such targets were themselves obscured to the tank gunner. In registering the target, however, the adjustment system used by the gunner differed from that of the artillery FOs. It was recommended that use of tank guns and lights be made part of the regular COP fire plan.