Mount Dingjun
In 217, Liu Bei started a campaign to seize Hanzhong from Cao Cao. After Xiahou Yuan was defeated and killed at the Battle of Mount Dingjun in 219, Cao Cao became alarmed and quickly arrived with reinforcements to resist Liu Bei. Both sides became locked in a stalemate, except for a clash at the Battle of Han River, before Cao Cao eventually decided to withdraw his forces, giving up Hanzhong to Liu Bei. Liu Bei subsequently declared himself "King of Hanzhong" after his victory.