定军山
In 217, Liu Bei launched a campaign to seize control of Hanzhong Commandery from Cao Cao's forces. Guo Huai did not participate in the initial battles as he was ill. After Xiahou Yuan was killed in action at the Battle of Mount Dingjun in 219, there was much panic and fear among Cao Cao's forces in Hanzhong as they had lost their commander. Guo Huai managed to restore order and stability within Cao Cao’s forces in two ways: First, he gathered and regrouped the soldiers who scattered when Xiahou Yuan was killed. Second, he nominated Zhang He to replace Xiahou Yuan as the commander of Cao Cao's forces in Hanzhong.