Liu Bei declares himself emperor as well, establishing Shu Han, after news of Cao Pi's ascension (and an accompanying false rumor that Cao had executed Emperor Xian) arrives in Liu Bei's domain of Yi Province (modern Sichuan and Chongqing).

Sun Quan, who controls the vast majority of modern southeastern and southern China, takes no affirmative steps one way or another, leaving his options open.

An armed conflict between Liu and Sun quickly develops, because in 219, Sun Quan's general Lü Meng had invaded and annexed Liu Bei's territory in Jing Province (modern Hubei and Hunan).

Guan Yu, the general appointed by Liu Bei to defend Jing Province, had been captured after his defeat and executed on Sun Quan's order.

Liu Bei was enraged by the sudden attack because Sun Quan was formerly his ally, and also due to his close relationship with Guan Yu.

Liu now wants to take vengeance on Sun for Guan Yu's death.

Many of his subjects, including Zhao Yun, oppose his decision, but Liu Bei ignores them.

As Liu Bei mobilized his troops in preparation for the attack on Sun Quan, another of his generals, Zhang Fei, is growing impatient with the preparations for war, so he imposes strict deadlines on his subordinates Fan Qiang and Zhang Da, but his subordinates fail to meet the time limit.

Zhang Fei disparages them before warning them that they will be executed under military law if they founder again.

Out of fear, Fan Qiang and Zhang Da kill Zhang Fei while he is asleep, cut off his head, and defect to Sun Quan.

Liu Bei is overwhelmed with grief over the loss of two of his generals, who had accompanied him since the beginning of his military career.

Zhang Fei's death hardens his decision to attack Wu for revenge.

Again, many Shu officials attempt to dissuade Liu Bei from attacking Sun Quan, but Liu dismisses their advice.

Eventually, Liu Bei departs from his capital, Chengdu, with a large army and advances towards Jing Province on both land and water (along the Yangtze River).

He leaves his chancellor Zhuge Liang and crown prince Liu Shan to defend Chengdu.