In the spring of 218, Liu Bei and Xiahou Yuan had faced each other for over a year. Liu Bei led the main army to the south of the Mian River () and ordered Huang Zhong to set up camps on Mount Dingjun, where Xiahou Yuan's encampment in the valley below could be easily monitored. One night, Liu Bei sent 10,000 troops to attack Zhang He in Guangshi and set fire to Xiahou Yuan's barricades. Xiahou Yuan then led a small detachment to put out the fire and sent the main army to reinforce Zhang He. Fa Zheng saw an opportunity for attack and signalled to Liu Bei to launch an assault. Liu Bei sent Huang Zhong to attack the weakened enemy from above. Huang Zhong targeted Xiahou Yuan's unit and completely routed it. Both Xiahou Yuan and Zhao Yong, Cao Cao's appointed Inspector of Yi Province, were killed in the battle.