On 15 September, Marines stormed ashore on three Inchon beaches. Despite difficulties inherent in effecting a landing there,[5] it was an outstandingly successful amphibious assault. The 1st and 5th Marines, with 1st Marine Aircraft Wing (1st MAW) assault squadrons providing close air support, quickly captured the port city of Inchon, Ascom City[6] to the east, and Kimpo Airfield. Advancing eastward the Marines approached the Han River that separates Kimpo Peninsula from the Korean mainland. Crossing this obstacle in amphibian vehicles, 1st Division Marines converged on Seoul from three directions. By 27 September, the Marines had captured the South Korean government complex and, together with the U.S. Army 7th Infantry Division, had severed the enemy’s main supply route (MSR) to Pusan. In heavy, close fighting near the city, other United Nations troops pursued and cut off major units of the NKPA.
[5] For a discussion of the hardships facing the landing force, see Montross and Canzona, USMC Ops Korea—Inchon, v. II, op. cit., pp. 41–42, 59–60, 62–64.
[6] In World War II, the Japanese developed a logistical base east of Inchon. When the Japanese surrendered, the Army Service Command temporarily took over the installation, naming it Ascom City. Maj Robert K. Sawyer, Military Advisers in Korea: KMAG in Peace and War (Washington: OCMH, DA, 1962), p. 43n.
Ordered back to East Korea, the Marine division re-embarked at Inchon in October and made an administrative landing at Wonsan on the North Korean coast 75 miles above the 38th Parallel. As part of the U.S. X Corps, the 1st Marine Division was to move the 5th and 7th Marines (Reinforced) to the vicinity of the Chosin Reservoir, from where they were to continue the advance northward toward the North Korean-Manchurian border. The 1st Marines and support troops were to remain in the Wonsan area.
While the bulk of the division moved northward, an unforeseen development was in the making that was to change materially the military situation in Korea overnight. Aware that the North Koreans were on the brink of military disaster, Communist China had decided to enter the fighting. Nine Chinese divisions had been dispatched into the area with the specific mission of destroying the 1st Marine Division.[7] Without prior warning, on the night of 27 November, hordes of Chinese Communist Forces (CCF, or “Chinese People’s Volunteers” as they called themselves) assaulted the unsuspecting Marines and nearly succeeding in trapping the two Marine regiments. The enemy’s failure to do so was due to the military discipline and courage displayed by able-bodied and wounded Marines alike, as well as effective support furnished by Marine aviation. Under conditions of great hardship, the division fought its way out over 78 miles of frozen ground from Chosin to the port of Hungnam, where transports stood by to evacuate the weary men and the equipment they had salvaged.
[7] Montross and Canzona, USMC Ops Korea—Chosin, v. III, p. 161.
This Chinese offensive had wrested victory from the grasp of General MacArthur just as the successful completion of the campaign seemed assured. In the west, the bulk of the Eighth Army paced its withdrawal with that of the X Corps. The UNC established a major line of defense across the country generally following the 38th Parallel. On Christmas Day, massed Chinese forces crossed the parallel, and within a week the UN positions were bearing the full brunt of the enemy assault. Driving southward, the Communists recaptured Seoul, but by mid-February 1951 the advance had been slowed down, the result of determined Eighth Army stands from a series of successive defensive lines.[8]
[8] On 9 January 1951, General MacArthur was “directed to defend himself in successive positions, inflicting maximum damage to hostile forces in Korea subject to the primary consideration of the safety of his troops and his basic mission of protecting Japan.” Carl Berger, The Korea Knot—A Military-Political History (Philadelphia: University of Pennsylvania Press, 1957), pp. 131–132, hereafter Berger, Korea Knot, quoted with permission of the publisher.
Following its evacuation from Hungnam, the 1st Marine Division early in 1951 underwent a brief period of rehabilitation and training in the vicinity of Masan, west of Pusan. From there, the division moved northeast to an area beyond Pohang on the east coast. Under operational control of Eighth Army, the Marines, with the 1st Korean Marine Corps Regiment attached for most of the period, protected 75 miles of a vital supply route from attack by bands of guerrillas. In addition, the Marines conducted patrols to locate, trap, and destroy the enemy. The Pohang guerrilla hunt also provided valuable training for several thousand recently arrived Marine division replacements.
In mid-February the 1st Marine Division was assigned to the U.S. IX Corps, then operating in east-central Korea near Wonju. Initially without the KMCs,[9] the Marine division helped push the corps line across the 38th Parallel into North Korea. On 22 April, the Chinese unleashed a gigantic offensive, which again forced UN troops back into South Korea. By the end of the month, however, the Allies had halted the 40-mile-wide enemy spring offensive.