Marine tanks were directed by Division to use their 90mm rifles to supplement 11th Marine howitzers in carrying out Corps fire plans. The tankers protested that their tubes had nearly reached the end of a normal life expectancy, with no replacements in sight. This plaint did not fall upon deaf ears at Corps Headquarters and two Army units, the 96th AFA Battalion and 17th FA Battalion, were assigned to fire the deep missions.[196] [196] 11thMar tel to G-2 1stMarDiv, 4 May 51; CG 1stMarDiv msg to CG X Corps, 9 May 51; X Corps msg X9613, 10 May 51. Eighth Army staff officers concluded that the enemy would launch his next effort in the center. Intelligence, according to General Van Fleet, “had noted for some 2 weeks prior to the May attack that the Chinese Communists were shifting their units to the east.” Nevertheless, the blow fell “much farther east than [was] expected.”[197] [197] Gen J. A. Van Fleet USA (Ret.), ltr of 24 Mar 58. Although the east offered the best prospects of surprise, a rugged terrain of few roads imposed grave logistical handicaps on the enemy. Moreover, UN warships dominated the entire eastern littoral. Despite these disadvantages, an estimated 125,000 Chinese attacked on the morning of 16 May 1951 in the area of the III and I ROK Corps between the U.S. 2d Infantry Division and the coast. Six CCF divisions spearheaded an advance on a 20-mile front that broke through the lines of the 5th and 7th ROK Divisions. Pouring into this gap, the Communists made a maximum penetration of 30 miles that endangered the right flank of the U.S. 2d Infantry Division. General Van Fleet took immediate steps to stabilize the front. In one of the war’s most remarkable maneuvers he sent units of the 3d Infantry Division, then in reserve southeast of Seoul, on a 70-mile all-night ride in trucks to the threatened area.[198] [198] Unless otherwise specified, accounts of the CCF offensive of 16 May 51 are based on the following sources: EUSAK _Cmd Rpt_, May 51, 12–18; 1stMarDiv _HD_, May 51; CO 7thMar msg to CG 1stMarDiv, 2015 17 May 51. The 1st Marine Division was not directly in the path of the enemy advance. During the early morning hours of 17 May, however, an enemy column made a thrust that apparently was intended as an end-run attack on the left flank of the 2d Infantry Division. Avoiding initially the Chunchon-Hongchon highway, Chinese in estimated regimental strength slipped behind the patrol base set up by a KMC company just west of the MSR (Map 12).