As the first Marine riflemen were kicking down doors throughout Yudam-ni during the afternoon of November 25, the Chinese were opening their Second Phase Offensive against 8th Army. By mid-morning, as the first Marine battalion command groups were moving into the valley of Yudam-ni, an entire American division of 8th Army, twenty-five thousand combat infantrymen, was cracking, plunging into headlong retreat. By lunchtime the Chinese in the west had unseated 8th Army's front and were infiltrating entire ten thousand-man divisions into the rears of successive 8th Army units.
No word of 8th Army's rout reached any tactical unit or headquarters in northeastern Korea. X Corps did not know that the Second Phase Offensive had begun. And the 7th Marines did not know that the road junction at Yudam-ni was not in the least bit vital any longer. In the absence of up-to-date information, however, the main body of 1st Marine Division was on the move toward Yudam-ni and the mountain tracks to the west.
The plan calling for the Marines to turn west to link up with 8th Army envisaged a brief concentration followed by an even wider dispersement. The 7th Marines, which had been leading the way into the mountains for over a month, was to hold at Yudam-ni and expand its domination far enough in all directions to ensure the security of the road net. The 5th Marines was to quit its intermediate positions east of the Chosin Reservoir, stage into Yudam-ni as soon as it could be relieved by elements of 7th Infantry Division, and take to the road leading westward from Yudam-ni into the vastness of the Taebek Mountain range. Elements of 8th Army, it was thought, were moving eastward on a reciprocal track. When joined with 8th Army, the 5th Marines was to turn northward and race for the Yalu River, the sooner to end the war.
As a consequence of preliminary moves in accordance with the corps plan, the entire fighting strength of 1st Marine Division was to be briefly concentrated within an area serviced by thirty-five miles of mountain road. All fighting elements of the division would be within supporting distance of all other fighting units for roughly forty-eight hours, from November 26 through November 28.
Though 8th Army was the greatest threat poised against the Yalu hydroelectric plants, the eighty-thousand-man X Corps had not been left out of the Chinese commander's plans. It would be hit, hard, when it entered the monstrous trap the Chinese field armies in northeastern Korea had prepared.
First Marine Division was withdrawn from west-central Korea in early October, 1950, and landed at Wŏnsan, North Korea's main east coast port, later in the month.
The seizure of Wŏnsan had been designed by MacArthur's GHQ-Tokyo as an end-run affair to rid geographically isolated northeastern Korea of the last vestiges of the fading NKPA. Operating as it had at Inch'ŏn, as part of United States X Corps (which also comprised the veteran 7th Infantry Division, and the newly arrived and untested 3rd Infantry Division), 1st Marine Division initially worked at clearing the coastal corridor around Wŏnsan. Later the Marines embarked upon a northerly drive toward the twin cities of Hamhung and Hŭngnam, a major commercial-industrial complex farther up the east coast.
Most of the narrow coastal strip had been secured by the end of October. While several ROK divisions led the advance to the Yalu, 1st Marine Division's vanguard advanced north and west from Hŭngnam on the narrow mountain road ascending toward the Chosin Reservoir, an intermediate objective beyond which the Marines had no firm goal.
Trained and equipped to operate as a cohesive, balanced fighting force, undertaking primarily amphibious missions, 1st Marine Division was, first, a bit out of its element on the Asian mainland and, second, thrown into some organizational confusion by the nature of simultaneous and divergent missions handed it by X Corps. More-over, the division had been roughly used in the Inch'ŏn-Sŏul drive, and it had not been brought back to strength following its withdrawal from west-central Korea.
First Marine Division was neither equipped nor trained for a protracted land campaign so far from its sources of supply, nor was it adequately outfitted for a mountain campaign in sub-zero weather. That the war was thought to be nearing a conclusion did not mitigate the fact that the Marines were being misused.
There is a natural disdain shared by military professionals for the doctrines of other branches of service, but the disdain is casual, usually friendly. There is, however, an enduring abrasive quality to the relationship between the United States Army and the United States Marine Corps. It arises from differing perceptions of the mission of the Marine Corps. Contrary to the views of Marines, many Army officers tend to see the capabilities of the two services as being
essentially interchangeable. Thus, in part, the use of an amphibious force in the North Korean mountains, and the feeling on the
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part of senior Marine officers that 1st Marine Division was being mishandled, possibly sacrificed.
Far from having a merely impossible mission, X Corps had no firm mission at all. It was to hold itself in a "state of readiness" even as it advanced piecemeal north and west from Hamhung into the truly great unknown of the northeast Korean hinterland.
Tiny elements of 7th Infantry Division, another component of X Corps, reached the Yalu, as did larger ROK Army forces which were working independently in the same zone of operations as X Corps. To the rear, the main bodies of 7th Infantry Division and 1st Marine Division were advancing northward, filling space but serving no vital strategic purpose.
X Corps lacked sufficient strength to amply secure all of north-eastern Korea, so was forced to rely upon an inadequate plan. Trusting to the superiority of Western arms and mechanized mobility, and hampered by having too much ground to cover, X Corps had a tendency to impose manifold tasks requiring its components to commit elements too small to perform adequately and too far apart to support one another.
During the second week of November, for example, the 5th and 7th Marines had been assigned parallel tracks along either shore of the Chosin Reservoir. Unable to support each other across the wide stretch of intervening water, the two regiments were on roads leading essentially nowhere, though both were bound vaguely for the Yalu. The third infantry regiment of 1st Marine Division, the 1st Marines, was just then being ordered up from duties nearer the coast to act as a reserve force and to guard the seventy-eight-mile-long Main Supply Route (MSR), the vulnerable one-lane road linking the Marines to their base at Hamhung.