Yi Province (specifically, its capital of Chengdu and its nearby commanderies) would serve as the foundation of the state of Shu Han during the Three Kingdoms period.

After the Battle of Red Cliffs, Sun Quan invited Liu Bei to take Yi Province with him, but the latter strongly rebutted the former, saying: "if you're going to conquer the land of Shu, I will loosen my hair and become a hermit in the deep hills.

However, instead of engaging Zhang Lu, Liu Bei halted his advance and focused on building up connections and gaining influence around the area in preparation for his takeover of Yi Province.

[15] Among them was an eccentric man named Peng Yang (Han dynasty), he quickly became friends with Pang Tong.

With Pang Tong's and Fa Zheng's support, Peng Yang joined Liu Bei's staff.

[16] Next year in 212, Liu Bei sent a letter to Liu Zhang where he told him that he needed more troops to divert Cao Cao's attention away from the east (where Sun Quan was under attack and asked for his help) and support Guan Yu against Yue Jin in Jing Province; he also mentioned that Zhang Lu was only looking to preserve his state and wouldn't engage in aggressive actions.

Zhao Jian (趙戩) believed that Liu Bei didn't have the talent to accomplish such a task, highlighting his past failures as well as Yi province's natural defences making it easy to defend and difficult to conquer.

However Fu Gan (傅幹) argued that: "Liu Bei is benevolent and tolerant and his men are willing to give their lives in his service.

[22] Wei Yan, who had just begun to serve under Liu Bei, was appointed as a bodyguard in his retinue; he made numerous achievements in several battles.

Zheng Du reasoned that Liu Bei's army was low on supplies and composed of new recruits who may not be loyal to him.

Liu Bei led his army along with Huang Zhong and Zhuo Ying to attack Fu County (涪縣; present-day Mianyang, Sichuan) and occupied the city.

[27] Following those success, Liu Bei organized a banquet where he expressed his great joy having conquered all the passes.

Pang Tong then drank and eat as before, when Liu Bei asked him who was in the wrong previously, he answered both of them.

[32] After Liu Bei conquered Mianzhu, he left Ma Su in charge as his Prefect (令).

After this, Liu Zhang's generals Fu Jin (扶禁), Xiang Cun (向存) and others led an army of more than 10 000 soldiers to attack his position.

Huo Jun used this opportunity and selected his best soldiers to lead a sortie; he inflicted them a heavy defeat beheading Xiang Cun during the battle.

Zhang Ren attempted to break the siege by leading his men onto the Wild Goose Bridge and charging Liu Bei's forces, but he was defeated and captured.

Following the Dian River (垫江), Zhang Fei broke through a thin defence line, and rendezvoused with Liu Bei.

[43] Zhao Yun and Zhuge Liang also conquered the surrounding counties and commanderies in the area before their arrival from another route.

[45] Liu Bei then surrounded Chengdu with the other armies[46][47] Ma Chao, a former Liang Province warlord and a vassal of Zhang Lu, was hated by Zhang Lu's subordinate Yang Bai (楊柏) along with others who were jealous of his ability and wanted to harm him; therefore Ma Chao wanted to use this opportunity to join Liu Bei.

"[49] He had Li Hui (who recently joined him at Mianzhu) welcome Ma Chao and provided him with soldiers and supplies to besiege Chengdu.

[50][51] Upon seeing Ma Chao's army to the north of Chengdu, the citizens inside the city were terrified and within 10 days following his arrival, Liu Zhang surrendered.

[54] During this time, the former Administrator of Guanghan (廣漢太守), Zhu Shuxian (朱叔賢) wanted to escape the city to surrender, however Liu Zhang heard about it and had him executed.

He used the gold and silver recently won to reward his soldiers and commanders; moreover he gave grain and silk to the common people.

[60] Then, he married Wu Yi's sister in an attempt to solidify his control on the newly conquered domain.

Sun Quan was furious when his envoy reported Liu Bei's words, and he sent Lü Meng and Ling Tong with another four officers to retake southern Jing Province.