Liu Zhang
In 212, Liu Bei and Liu Zhang turned hostile towards each other and waged war. Zhuge Liang led a detachment of Liu Bei's forces left in Jing Province to join his lord in attacking Liu Zhang. Guan Yu remained behind to defend Jing Province. In 215, Liu Bei had defeated much of Liu Zhang's forces and besieged him in his capital of Chengdu. Liu Zhang surrendered and yielded Yi Province to Liu Bei. The province became Liu Bei's new base, and he used the mountainous surroundings as natural defences against Cao Cao in the north.