Korea on 1 October. The momentum of the attack was maintained, and the race to the North Korean capital, Pyongyang, ended on 19 October when elements of the division and the Republic of Korea Army (ROK) 1st Infantry Division captured the city. The advance continued, but against unexpectedly stiffening resistance. The Chinese People's Volunteer Army (PVA) entered the war on the side of North Korea, making their first attacks in late October. On 28 October 1950, Eighth Army commander General Walton Walker relieved the 1st Cavalry Division of its security mission in Pyongyang. The division's new orders were to pass through the ROK 1st Division's lines at Unsan and attack toward the Yalu River. Leading the way on the twenty-ninth, the 8th Cavalry regiment departed Pyongyang and reached Yongsan-dong that evening. The 5th Cavalry Regiment arrived the next morning, with the mission to protect the 8th Cavalry regiment's rear. With the arrival of the 8th Cavalry Regiment at Unsan on the 31st, the ROK 1st Division redeployed to positions northeast, east, and southeast of Unsan; the 8th Cavalry took up positions north, west, and south of the town. Meanwhile, the ROK 15th Regiment was desperately trying to hold its position east of the 8th Cavalry, across the Samt'an River. During the afternoon of 1 November, the PVA attack north of Unsan gained strength against the ROK 15th Regiment and gradually extended to the right flank of the 1st Battalion, 8th Cavalry. At nightfall, the 1st Battalion controlled the northern approaches to the Samt'an River, except for portions of the ROK 15th Regiment's zone on the east side. The battalion's position on the left was weak; there were not enough soldiers to extend the defensive line to the main ridge leading into Unsan. This left a gap between the 1st and 2nd Battalions. East of the Samt'an the ROK 15th Regiment was under heavy attack, and shortly after midnight it no longer existed as a combat force. At 19:30 on 1 November, the PVA 116th Division attacked the 1st Battalion, 8th Cavalry, all along its line. At 21:00 PVA troops found the weak link in the ridgeline and began moving through it and down the ridge behind the 2nd Battalion, penetrating its right flank and encircling its left. Now both the 1st and 2nd Battalions were engaged by the enemy on several sides. Around midnight, the 8th Cavalry received orders to