 Undetected by US and South Korean intelligence, the 13th Army Group crossed the border on 16 October and penetrated up to into North Korea.Meanwhile, on 27 October the Middlesex continued the brigade's advance, and was involved in a sharp fight in the hills west of the river near the village of Yongsong-ni, killing 35 KPA and capturing 80 prisoners, while American aircraft destroyed 10 KPA T-34 tanks and two SU-76 self-propelled guns.The following day the Argylls took over as the lead battalion.