As it happened, the regimental executive officer, Lieutenant Colonel Stewart, worked out a plan that did not include any such novelty. A narrow ford was discovered that would get the 1st and 2d Battalions across while the 3d rode in DUKWs. Light enemy opposition of a rear guard nature was encountered but the regiment completed the operation without casualties. Stewart reported to the regimental CP and learned that a jeep waited to take him on the initial lap of his homeward journey. He was the last man to leave Korea of the 1st Provisional Marine Brigade, which had landed at Pusan on 2 August 1950.[147] [147] Col J. L. Stewart, ltr of 25 Oct 57. After reaching their prescribed objectives, the 5th Marines and KMC Regiment were relieved on 5 April by elements of the 7th Infantry Division of X Corps. Meanwhile, the 7th Marines, attached to the 1st Cavalry Division, advanced northward with the 7th and 8th Cavalry Regiments. Little opposition developed and on 4 April the Marines were among the first Eighth Army troops to recross the 38th Parallel. General Ridgway published another operation plan on 6 April 1951 and designated new Eighth Army objectives to the northward. The purpose was to threaten the buildup for the forthcoming CCF offensive that was taking place behind the enemy lines in the so-called “Iron Triangle.” This strategic area, one of the few pieces of comparatively level real estate in central Korea, was bounded by Kumhwa, Chorwon, and Pyongyang (Map 14). A broad valley containing a network of good roads, it had been utilized by the Chinese for the massing of supplies and troops. Experience had proved that interdictory bombing could not prevent the enemy from nourishing an offensive, even though the FEAF had complete control of the air over roads and rail lines of a mountainous peninsula. The Chinese, though hampered in their efforts, had been able to bring up large quantities of supplies under cover of darkness. General Ridgway determined, therefore, to launch his ground forces at objectives threatening the Iron Triangle, thus forcing the enemy to fight. On 8 April, in preparation for the new effort, the 1st Marine Division was directed by IX Corps to relieve the 1st Cavalry Division on Line KANSAS and prepare to attack toward Line QUANTICO (Map 8). _Renewal of Division’s CAS Problems_ By this time, after three months of various sorts of operational difficulties, VMF-311 was riding a wave of efficiency. The distance from the operating base to the combat area emphasized the superior speed of the F9Fs. The Panther jets could get into action in half the time required by the Corsairs. The jets were more stable in rocket, bombing, and strafing runs. They were faster on armed reconnaissance and often were pouring it into the enemy before he could disperse. These advantages offset the high fuel consumption of the F9Fs and made them ideal planes for close air support.