The 1st Marines had outfought and outgamed a tough enemy. Never again, after the 10th, was the NKPA resistance quite as determined. The 3d Battalion led the other two during the next few days. There was plenty of fighting for all three, but the result was never again in doubt. By the late afternoon of 14 June the regiment was in position on the BROWN Line. This was the unofficial name for an extension of the KANSAS Line some 3,000 yards north. It had been requested by Colonel Brown when he realized that positions along the KANSAS Line were completely dominated by the next ridge to the north. The change made necessary a continued advance by the KMCs on the right to tie in with the 1st Marines. The so-called BROWN Line was then officially designated the modified KANSAS Line. _7th Marines Committed to the Attack_ For several days General Thomas had been concerned over the heavy casualties suffered by his command. In order to give greater impetus to the Division effort, he decided to commit the reserve infantry regiment, the 7th Marines (minus one battalion held back as Division reserve) to complete the occupation of the modified KANSAS Line. On 8 June, Colonel Nickerson’s regiment (minus 3/7) moved into an assembly area between the 1st Marines and the KMCs, ready to attack in the morning. Ahead stretched a narrow but difficult zone of advance up the valley of the So-chon River (Map 15). Tank-infantry patrols went forward to select favorable positions for the jumpoff, and engineers worked throughout the daylight hours to clear the valley roads of mines. Despite their best efforts, 10 Marine tanks were lost to mines during the first week.[237] [237] Unless otherwise noted, this section is based on the _HD_s of the 1stMarDiv, 7thMar, 1/7, 2/7, and 3/7 for Jun 51. As the two battalions advanced on the morning of the 9th they came under heavy enemy artillery and mortar fire. Nevertheless, they secured Hill 420 and dug in before nightfall. On the 10th Rooney’s 1/7 advanced along the ridgeline to support the attack of Meyerhoff’s 2/7 up the valley floor. The maneuver was carried out successfully in spite of NKPA automatic weapons and mortar opposition. Contact was established with KMC forward units at dusk. Sixteen POWs were taken by the 7th Marines and 85 North Korean dead were counted on the objectives. The two battalions continued the attack throughout the next week. The 3d Battalion of the 7th Marines remained General Thomas’ sole Division reserve until he committed it on the afternoon of 18 June.