To that end, Li Keju had Li Quanzhong take 60,000 soldiers and attack Yiwu's Yi Prefecture (易州, in modern Baoding). Li Quanzhong's subordinate Liu Rengong dug a tunnel into Yi Prefecture's city walls, and the Lulong troops were able to use the tunnel to capture it. However, after the Lulong troops took Yi Prefecture, they became arrogant and did not take precautions against an Yiwu counterattack. Wang Chucun thereafter had his soldiers put on sheepskin at night to appear to be sheep and approached Yi. The Lulong troops thought that there was a large herd for them to pillage, and therefore came out of the city to seize it. They were surprised by the Yiwu soldiers, who attacked and retook Yi. Li Quanzhong, after the defeat, fled back toward You Prefecture (幽州, i.e., Fanyang).
