Records of the Three Kingdoms
Liu Zhang, courtesy name Jiyu, was from Jingling in Jiangxia. His father Liu Yan was governor of Yi Province at the end of the Han. After Liu Yan died the officers put Liu Zhang in his place. He was mild, and his laws were loose. Zhang Lu in Hanzhong pressed him. Zhang Song and Fa Zheng urged him to invite Liu Bei in, as a guard against both Zhang Lu and Cao Cao.
In 211 Liu Bei brought his army to Jiameng. The next year Liu Bei broke with Liu Zhang and attacked Fucheng and Luo. Pang Tong died from an arrow during the siege of Luo. In 214 Liu Bei besieged Chengdu for several tens of days. Liu Zhang said that he and his father had been in Yi for more than twenty years without real kindness to the people, and that he would not fight on. He opened the city. Liu Bei moved him to Gong’an and returned his property and the title General Who Inspires Awe. He died of illness at Gong’an at the end of Jian’an.
Romance of the Three Kingdoms
The novel makes Liu Zhang so mild he is nearly unable to rule. Zhang Song offers a map, Fa Zheng works from inside, and Liu Bei turns on him at Fucheng. Yi Province goes step by step. Under the walls of Chengdu he surrenders in tears and calls the people’s suffering his own fault.
The book needs someone who will hand Yi over, so his kindness becomes an inability to hold land. The decision to surrender is in the histories.
Reference: Wikipedia · Liu Zhang