The Marines at Yudam-ni were ordered to retreat, T. R. Fehrenbach explains (in This Kind of War), but it would be called an attack to the south:
At Yudam-ni only the wounded and those who could not walk were placed aboard vehicles; many men who were hurt had to walk. Then, the infantry battalions leading the way, the regiments came out through Toktong Pass.
They came out intact, with their jeeps, guns, tractors, and trucks. Strapped to the fenders and hoods of vehicles lay bloody, half-frozen Marines. Others lay across gun barrels, or were carried in ox-drawn sleds taken from Koreans. It was not a motor march. It was a tactical battle most of the way, against Chinese who held the hills in depth. But the Marines came out, for three reasons:
One, Davis’ and Taplett’s men were able to climb the encircling mountains, knock the enemy off the ridges, drive them across the high timber. Moving by night, attacking cross-country in savage terrain and savage weather, these Marines took the Chinese in the flank, and by surprise. In the face of incredible hardship, the Marines were able to mount offensive action — and Barber’s Fox Company, 7th Marines, had been able to hold off two enemy regiments for six days, preventing the Chinese from closing their ring. If Barber had not held, the way would have been much more difficult.
Two, Marine air from the 1st Air Wing near Hamhung, carrier pilots from Philippine Sea and Leyte, and Air Force supply planes flew constantly over the column. Marine aircraft strafed, bombed, and napalmed as close as fifty yards from the leading elements. Marine air, flying so low as to touch the mountains, knocked out roadblock after roadblock, as fast as the Chinese assembled them. Marine pilots volunteered to fly night missions in the dangerous mountains.
Hour after hour, the sky above the American troops was black with friendly aircraft, and without them, in spite of their courage, in spite of all else, the ground troops would never have come out.
Third, General Sung Shih-lun had gambled. In the horrendous terrain, he had never been able to bring his full manpower to bear on the embattled Marines, outnumbered though they were. By pushing his men across the mountains from the Yalu in fourteen days, he had had to leave most of his supply and artillery behind — and as the battle continued day after day, stinging night after night, even Sung Shih-lun’s sturdy peasants neared collapse.
The Chinese had come into Korea well fed and well clothed, but they were without supply, depending on the countryside for future livelihood. Near-starvation and dysentery hit them, too. The hardy Chinese peasant, while brought up to hardship, was no superman. As the Marines neared Hagaru, weary CCF units deserted their peaks under air attack. The Marines found some who had thrown away their arms and who lay huddled together in the snow, freezing and apathetic, trying only to stay alive.
1. Barber hit three times yet continued to command his company. Action indeed worthy of the MoH.
2. Chinese from the elements suffering worse than the Marines. Chinese units at Chosin aftermath of the battle sent back to China to be reconstituted.