樊城之戰
The first phase of the plan was completed in 214 when Liu Bei gained control of southern Jing Province and Yi Province. Between 217 and 219, Liu Bei launched a campaign to seize control of Hanzhong Commandery, the "northern gateway" into Yi Province, and succeeded in capturing it from Cao Cao's forces. In 219, Liu Bei's general Guan Yu, whom Liu Bei had left in charge of Jing Province, started the Battle of Fancheng against Cao Cao's forces. However, the Sun Quan–Liu Bei alliance ("Sun–Liu alliance"), which Zhuge Liang played an instrumental role in creating, broke down when Sun Quan sent his forces to attack and seize Liu Bei's territories in Jing Province while Guan Yu was away at the Battle of Fancheng. Guan Yu was captured and executed by Sun Quan's forces. Between 221 and 222, Liu Bei started the Battle of Xiaoting/Yiling against Sun Quan in an attempt to retake Jing Province, but failed and suffered a disastrous defeat. After Liu Bei died in 223, his son Liu Shan succeeded him as emperor of Shu, with Zhuge Liang serving as regent. In the same year, Zhuge Liang made peace with Sun Quan's Eastern Wu regime and reestablished the Sun–Liu alliance (now the Wu–Shu alliance) against Wei, the regime established by Cao Cao's son and successor, Cao Pi.