In March 1952, the US 1st Marine Division was transferred to US I Corps and moved onto the Jamestown Line, the United Nations' Main line of resistance across Korea. The segment of the Jamestown Line assigned to the 1st Marine Division extended southwest from the Samichon River and the left flank of the British 1st Commonwealth Division, crossed the 38th Parallel (the original geopolitical border between North and South Korea) shifted to the south bank of the Imjin River in the vicinity of Munsan-ni, continued to the conflux of the Imjin and Han River, and then followed the south bank of the Han past the Kimpo Peninsula. Opposing the Marines on the Jamestown Line, the Chinese People's Volunteer Army had the 65th and 63rd Armies, totaling 49,800 troops. The 7th Marine Regiment took over seven outposts when it relieved the 5th Marine Regiment on the Jamestown Line in early October, renaming them, from left to right, Carson, Reno, Vegas, Berlin, Detroit, Frisco, and Seattle. At the point, later known as the Hook, where the frontline veered southward toward the boundary with the 1st Commonwealth Division, the 7th Marines set up Outpost Warsaw. A second new outpost, Verdun, guarded the boundary between the Marine and Commonwealth divisions. An average of 450 yards separated four of these outposts, Detroit, Frisco, Seattle and Warsaw, which occupied hills lower than those on the left of the regimental line and therefore were more easily isolated and attacked.
