This official U.S. Marine Corps history provides unique information about important aspects of the Korean War, with material on the 1st Marine Division, Imjin River, Kimpo Peninsula, the 1st Marine Aircraft Wing, Medal of Honor Winners, and General Selden. Here is an excerpt:
The 1st Marine Division— including the Kimpo Provisional Regiment, the amphibian tractor battalion, the Korean Marines, and the two Marine regiments on line —defended some 60,000 yards, two to four times that normally assigned to a similarly reinforced division. Within the division, a battalion, one third of the infantry strength of a regiment, held a frontage of from 3,500 to 5,000 yards, while a rifle company, one-third the infantry strength of a battalion, could man a sector as wide as 1,700 yards. A line of outposts of varying strength located on hills as far as 2,500 yards in front of the main line of resistance, improved the security of the Jamestown positions, but forced the Marines to spread themselves even thinner along the front. To defend the division's broad segment of the Jamestown Line, General Selden commanded a total of 1,364 Marine officers, 24,846 enlisted Marines, 1,100 naval officers and sailors— mostly doctors, dentists, and medical corpsmen—and 4,400 Korean Marines.
The Imjin River, flowing southwest from the division's right flank, lay behind the main line of resistance until the defenses crossed the river west of Munsan-ni. Since only three bridges—all of them vulnerable to damage from floods —spanned the Imjin, the stream, when in flood, posed a formidable obstacle to the movement of supplies and reinforcements. A single rail line to Munsan-ni served the region and the existing road net required extensive improvement to support military traffic. The terrain varied from mountainous, with sharp-backed ridges delineating narrow valleys, to rice paddies and mud flats along the major rivers. West-central Korea promised to be a difficult place for the reinforced but widely spread 1st Marine Division to conduct sustained military operations.
General Selden's Marines took over their portion of the Jamestown Line from South Korean soldiers manning an area that had become something of a backwater, perhaps because of its proximity to Kaesong, where truce talks had begun, and Panmunjom where they were continuing. "It was quite apparent," Seldon noted, "that the relieved ROK [Republic of Korea] Division had not been conducting an aggressive defense." As a result, the Marines inherited bunkers built to protect more against the elements than against enemy mortars and artillery. Korean noncombatants, taking advantage of the lull, had resumed farming in the area, moving about and creating concealment for possible Chinese infiltration.