On 16 September Eighth Army began its breakout from the Pusan perimeter, however, 25th Infantry Division was still fighting KPA forces behind its lines, and KPA strongpoints existed on the heights of Battle Mountain, P'il-bong, and Sobuk-san. Kean felt that the division could advance along the roads toward Chinju only when the mountainous center of the division front was clear. He therefore believed that the key to the advance of the 25th Division lay in its center where the KPA held the heights and kept the 24th Infantry Regiment under daily attack. The 27th Infantry on the left and the 35th Infantry on the right, astride the roads between Chinju and Masan held their positions and could not advance until the situation in front of the 24th Infantry improved. To carry out his plan, Kean organized a composite battalion-sized task force on September 16 under command of Major Robert L. Woolfolk, commanding officer of the 3rd Battalion, 35th Infantry, and ordered it to attack Battle Mountain and P'il-bong the next day, with the mission of restoring the 24th Infantry positions there. On September 17–18 the task force repeatedly attacked these heights, heavily supported by artillery fire from the 8th and 90th Field Artillery Battalions and by numerous air strikes, but KPA automatic fire from the heights drove back the assaulting troops every time with heavy casualties. Within one day, A Company, 27th Infantry, alone suffered 57 casualties. The 24th Infantry bogged down behind Battle Mountain. Woolfolk's force abandoned its effort to drive the KPA from the peaks after its failure on September 18, and the task group was dissolved the next day. North Korean withdrawal On September 19 the UN discovered the KPA had abandoned of Battle Mountain during the night, and the 1st Battalion, 24th Infantry, moved up and occupied it. On the right, the 35th Infantry began moving forward. There was only light resistance until it reached the high ground in front of Chungam-ni where hidden KPA soldiers in spider holes shot at 1st Battalion soldiers from the rear. The next day the 1st Battalion captured Chungam-ni, and the 2nd Battalion captured the long ridge line running northwest from it to the Nam River. Meanwhile, the KPA still held strongly against the division left where the 27th Infantry had heavy fighting in trying to move forward. The KPA withdrew from the Masan area the night of September 18–19.