It was the misfortune of the 1st Marine Division to have perhaps the least lucrative zone of action in all Korea for the peninsula-wide turkey shoot. A chaos of jagged peaks and dark, narrow valleys, the terrain alone was enough to limit an advance. Even so, the Marines inflicted 1,870 counted KIA casualties on the Communists in May and captured 593, most of them during the last eight days of the month. General Almond congratulated the Division for its accomplishment of “a most arduous battle task. You have denied [the enemy] the opportunity of regrouping his forces and forced him into a hasty retreat; the destruction of enemy forces and materiel has been tremendous and many times greater than our own losses.”[203] [203] CG X Corps msg of 1500, 3 Jun 51; 1stMarDiv _HD_, May 51. _Plan to Cut Off Communists_ The 187th Airborne Regimental Combat Team, released from IX Corps reserve, arrived in the Hongchon area on 21 May and took a position between the 1st Marine Division on the left and the 2d Infantry Division on the right. Two days later X Corps gave the Marines the mission of securing the important road center of Yanggu at the eastern end of the Hwachon Reservoir (Map 13). Elements of the 2d Infantry Division, with the 187th Airborne RCT attached, were meanwhile to drive northeast to Inje after establishing a bridgehead across the river Soyang. From Inje the 187th (reinforced) would continue to advance northeast toward its final objective, Kansong on the coast. After linking up with I ROK Corps, the Army regiment might be able to pull the drawstring on a tremendous bag of prisoners--all the CCF forces south of the Inje-Kansong road. There was, however, a big “if” in the equation. The Communists were falling back with all haste, and it was a question whether the bag could be closed in time. [Illustration: 1st Marine Division Drive To Yanggu 23–31 May Showing Regimental Routes MAP 13] The 1st Marine Division jumped off at 0800 on 23 May with the 1st and 5th Marines abreast, the 1st on the left. Both regiments advanced more than 5,000 yards against negligible opposition. During the course of this attack the 1st Marines experimented by calling an air strike in the hope of detonating an entire mine field. The results were disappointing. Live mines were blown to new locations, thus changing the pattern, but few exploded.[204] [204] 2/1 _HD_, May 51. The 7th Marines was relieved on the 23d by elements of the 7th Infantry Division (IX Corps) and moved to the east for employment on the Marine right flank. The KMC Regiment, relieved by other IX Corps units, went into Division reserve.[205] [205] 1stMarDiv _HD_, May 51.