Chaoyang, Liaoning
The base of Wuhuan power was located at Liucheng (柳城; southwest of present-day Chaoyang, Liaoning), and the obvious line of attack from Wuzhong was through the plains along the coastline of the Bohai Sea. However, in August or early September, the monsoon season set in and the heavy rains flooded the low-lying areas and drenched the roads in mud, making the terrain impassable. The Wuhuan also anticipated such an attack route and held the river crossings, and for some time Cao Cao's army could not advance.