Movement of the 1st Marine Division to the west was part of an Eighth Army master plan to strengthen UN defenses and at the same time to enable South Korean forces to assume increased responsibility in the defense of their homeland. The tactical realignment in the spring of 1952 put more South Korean infantry units on the main line of resistance and buttressed the fighting front with five corps sectors instead of four. In the far west, the I Corps positions were newly manned (left to right) by the 1st Marine, 1st Commonwealth, 1st ROK, and the U.S. 45th Infantry Divisions. Next in line was IX Corps, whose left boundary General Van Fleet[70] had shifted further west, which now had a divisional line up of the ROK 9th on the left, the U.S. 7th in the center, and the U.S. 40th on the right.
[70] General Van Fleet, CG, EUSAK since April 1951, had advocated a program in which South Korean troops would be rigorously trained to take over an increasingly greater part of the UNC defense efforts in Korea. See Mark W. Clark, From the Danube to the Yalu (New York: Harper & Brothers, 1954), p. 185, hereafter Clark, Danube to Yalu, quoted with permission of the publishers.
To fill in the central part of the EUSAK front where the change of IX Corps boundary had created a gap in the line, the UN commander inserted the ROK II Corps with three divisions (ROK 6th, ROK Capital, and ROK 3d) forward. Immediately to the right of this new ROK corps sector, the X Corps continued in approximately its same position on the east-central front. Its ROK 7th and U.S. 25th Divisions remained on line, while the ROK 8th had advanced to the former sector of the Marine division in the wild Punchbowl country. At the far right of the UN line, the ROK I Corps front was held by the ROK 11th Division at the X Corps boundary and the ROK 5th along the Sea of Japan. By 1 May 1952, nine Republic of Korea divisions had been emplaced on the UNC main defense line, three more than had been there in mid-March.
Throughout Korea in March and April there had been a general stagnation of offensive action on both sides because of fog, rain, and mud. In May, however, the Chinese launched no less than 30 probing attacks against the ROK 1st Division in the I Corps sector, without gaining any significant advantage. To the right, the enemy and the U.S. 45th Division traded blows in several patrol actions. In June, major EUSAK combat action was still centered in the 45th’s sector, but the following month was marked by sharp battlefront clashes in nearly all Eighth Army division areas. For a two-week period in July and August, heavy seasonal rains limited both ground and air action. With the return of normal weather, heavy fighting again broke out, this time concentrated in the I Corps sector. This action did not abate until late August, when the onset of the heaviest rains of the season again drastically reduced military operations.
Communist ground activity in the spring of 1952 was marked by increased artillery support which resulted in telling damage to UN infantry and artillery positions. Thus, during May, the enemy expended approximately 102,000 artillery and mortar rounds against the Allied front, roughly 12 times the number fired the previous July, just prior to the period of stabilized battlelines in Korea. The artillery buildup was accompanied by a sharp decrease in hostile air support activities. While the Chinese had flown 3,700 jet sorties during the first month of 1952, by June the monthly total had dropped to 308.
As part of the balanced military forces, Allied air and sea units continued their active defense in support of UN ground units. Beginning in late May, Fifth Air Force shifted the emphasis of its destructive effort from interdiction of communication routes to the bombing of selected industrial targets. Naval air was committed to support the FAF programs. At sea, ships steamed almost at will to sustain the U.S. lifeline. Underscoring the complete UN control of Korean waters, large naval vessels offshore fired their big guns in support of ground troops. Off both the west and east coasts, Task Force (TF) 95 maintained its blockade of North Korean ports and reduced the extent of water travel that enemy craft could safely undertake. This same naval force was responsible for the Allied defense of islands located off the east and west coasts of Korea.
Defense of West and East Coast Korean Islands[71]
[71] Unless otherwise noted, the material in this section is derived from: PacFlt EvalRpts No. 4, Chap. 9; No. 5, Chap. 8; West Coast Island Defense Element ComdDs, Feb-Oct 52, hereafter WCIDE ComdD, with date; East Coast Island Defense ComdDs, Jan-Oct 52, hereafter ECIDE ComdD, with date; Col William K. Davenport ltr to CMC, dtd 27 Jun 52, Subj: Type D Report of duty as Commander West Coast Island Defense Element (CTE 95.15); Cagle and Manson, Sea War, Korea; Field, NavOps, Korea.
Just off the northwest Korean mainland a string of islands extends from the mouth of the Yalu River down around the peninsula to Pusan in the southeast. Most of these islands are tiny and are located south of the 38th Parallel. Only a few lie off the east coast, and these are clustered primarily in the North Korean harbor of Wonsan. By early 1951, UN forces exercised control over most of the Korean islands. Their tactical importance is shown from their diverse use as sites for UN Command intelligence activities, USAF radar installations, locations for the emergency landing strips used by Allied planes, bases for U.S. search and rescue operations, and as springboards for possible thrusts into enemy rear areas.[72]
[72] Evidence of Chinese concern about such rear area attacks is apparent in the countermeasures taken: “Order of Battle reports indicated that a total of three North Korean Corps and three Chinese Communist Armies were engaged in coastal defense operations on the east and west coasts of North Korea.” PacFlt EvalRpt, No. 5, p. 8-79.