However, another Song force on the east led by Cao Bin was destroyed by a Liao force led by Yelü Xiuge, and tens of thousands of Song soldiers perished. As the Liao force with over 100,000 soldiers marched westward, Pan and Yang Ye were in Daizhou and received orders to help the civilians of the four conquered prefectures retreat back to Song territory. When Huanzhou fell to the Liao army, Yang told Pan, "Liao forces are strong and we must not fight them." He proposed a detailed plan to maximize the safety of the civilians from the 3 remaining prefectures. Per this plan, the Yunzhou civilians would leave first. The main Song force would advance from Daizhou to Yingzhou, drawing the main Liao force, thus allowing the Shuozhou civilians to leave and move to a valley called Shijiegu (石碣谷), which could be defended by a thousand soldiers with arrows. Finally a cavalry reinforcement would help the main Song force retrieve the Yingzhou civilians. The generals defending Shuozhou and Yunzhou would be notified of the plan to coordinate activities.