39th Army (115th, 116th, and 117th Divisions), estimated total strength, 19,538; 40th Army (118th, 119th, and 120th Divisions), estimated total strength, 25,319. The 20th and 26th, it may be recalled, were two of the CCF armies opposing the 1st Marine Division during the Chosin Reservoir breakout. It was a satisfaction to the Marines that their opponents of December 1950 had evidently needed from three to four months to reorganize and get back into action. In CCF reserve on 21 April 1951 were the 42d and 66th Armies, both located in the Iron Triangle to the enemy’s rear. The former included the 124th, 125th, and 126th Divisions--the 124th being the unit cut to pieces from 3 to 7 November 1950 by the 7th Marines in the war’s first American offensive action against Chinese Red adversaries. _Hwachon Occupied by KMC Regiment_ At 0700 on the 21st the 1st Marine Division resumed the attack toward Line QUANTICO with the 7th Marines on the left, the 5th Marines in the center, the KMC Regiment on the right, and the 1st Marines in reserve. Negligible resistance awaited the Marines and other IX Corps troops during advances of 5,000 to 9,000 yards. An ominous quiet hung over the front as green wood smoke limited visibility to a few hundred yards. On the Marine left the 6th ROK Division lost touch, opening a gap of 2,500 yards, according to a message from Corps to the 1st Marine Division. The ROK commander was ordered by Corps to restore lateral contact. This incident would be recalled significantly by the Marines when the CCF blow fell.[152] [152] 1stMarDiv _HD_ Apr 51, 47–48; CO 7thMar msg to CG 1stMarDiv, 1830 21 Apr 51. The KMC Regiment had the mission of finishing the fight for control of the Hwachon Reservoir area. Early in April the 1st Cavalry Division and the 4th Ranger Company, USA, had been repulsed in attempts to fight their way across the artificial lake in rubber boats. The enemy retaliated by opening the penstocks and spillway gates. Considering that the dam was 275 feet high and the spillway 826 feet long, it is not surprising that a wall of water 10 feet high roared down the Pukhan Valley into areas recently occupied by IX Corps units.[153] [153] Capt D. E. Fowler, “Operations at the Hwachon Dam, Korea,” _The Military Engineer_, Jan-Feb 1952, 7–8. Both Army and Marine engineers were on the alert, having been warned by aerial observers. They cut three floating bridges loose from one bank or another, so that they could ride out the crest of the flood. Thanks to this precaution, only temporary damage and interruption of traffic resulted.[154] [154] 1stMarDiv _HD_, Apr 51.