_The Marines in Operation_ MIXMASTER In the spring of 1952, when the UN and Communist forces were facing each other from static positions and fighting local engagements, Operation MIXMASTER took place. MIXMASTER was a complicated rearrangement of UN divisions across the entire Korean front during March, and involved the shuffling of about 200,000 men and their equipment over distances from 25 to 180 miles. It was a severe test of Eighth Army mobility.[368] [368] Col B. T. Hemphill, Comments, 30 Jan 59. General Van Fleet visited the 1st Marine Division CP on 12 March 1952, and announced an important command decision. After six months of defensive warfare in the same sector along Line MINNESOTA (20 September 1951 to 16 March 1952) the Division was to move across the peninsula to West Korea. [Illustration: EUSAK DISPOSITIONS 15 MARCH 1952 MAP 22] The Marines had orders to relieve the 1st ROK Division and take over a sector at the extreme left of the Eighth Army line under the operational control of I Corps (Map 22). There they would have the responsibility for blocking Korea’s historic invasion route to Seoul. The reasons behind this EUSAK decision were summarized in the 1st Marine Division report as follows: (1) The abandonment of plans to carry out an amphibious envelopment somewhere on the east coast; (2) Concern over weaknesses in the Kimpo area defenses; (3) The overall situation would not permit loss of ground on the EUSAK left (South Korea) as this would endanger the capital at Seoul; that if retraction of lines was necessary, territory could better be sacrificed on the right (North Korea) where the country was mountainous and had little economic or strategic value.[369] [369] 1stMarDiv _HD_, Mar 52, 1–2. Up to this time the four corps of the Eighth Army had defended a 125-mile front across the peninsula (Map 22) with the following units in line from left to right on 15 March 1952. I CORPS--ROK 1st Division; British Commonwealth Division; U.S. 3d Infantry Division (-); U.S. 45th Infantry Division (Oklahoma National Guard); ROK 9th Division. In reserve were the ROK 8th Division and RCT-65 of the U.S. 3d Infantry Division. IX CORPS--U.S. 2d Infantry Division; ROK 2d Division; U.S. 40th Infantry Division (California National Guard); ROK 3d Division. In reserve were the U.S. 7th Infantry Division (-), RCT-17 of that Division, and the ROK Capitol Division. X CORPS--ROK 7th Division; U.S. 25th Infantry Division; U.S. 1st Marine Division (including 1st KMC Regiment). In reserve was the ROK 6th Division (-). I ROK CORPS--ROK 5th Division (-). In reserve was the ROK 11th Division (-).[370] [370] EUSAK _Cmd Rpt_, Mar 52, 13–14. Allowing for a few changes, these were the positions held by major EUSAK units through the winter of 1951–1952.