Editing Sun Quan (section)

==Breaking of alliance with Liu Bei==
In 219, [[Guan Yu]] advanced north, attacking [[Fancheng District|Fancheng]], scoring a major victory over [[Cao Ren]]. While Fancheng did not fall at this time, Guan Yu put it under siege, and the situation was severe enough that Cao Cao considered moving the capital away from Xu. However, Sun Quan, resentful of Guan Yu's prior constant instigation of hostilities (including seizing Sun's food supplies to use for his campaign north), took the opportunity to attack Guan from the rear, and Guan's forces collapsed. Guan Yu was captured by forces under Lü Meng and [[Jiang Qin]]; Guan Yu was executed, [[Jing Province]] came under Sun's control, and the Sun-Liu alliance ended.

After Cao Cao's death in 220, Cao Pi forced Emperor Xian to yield the throne to him, ending the Han dynasty and establishing the state of [[Cao Wei]]. Sun Quan did not immediately submit to Wei or declare independence after Cao Pi's enthronement, but took a wait-and-see attitude; by contrast, in early 221, Liu Bei declared himself emperor, establishing the state of [[Shu Han]]. Immediately, Liu Bei planned a campaign against Sun Quan to avenge Guan Yu. After attempting to negotiate peace and receiving no positive response from Liu Bei, fearing attack on both sides, Sun Quan became a vassal of Wei. Cao Pi's strategist [[Liu Ye (Three Kingdoms)|Liu Ye]] suggested that Cao Pi decline—and in fact attack Sun Quan on a second front, effectively partitioning Sun's domain with Shu, and then eventually seek to destroy Shu as well. Cao Pi declined, in a fateful choice that most historians believe doomed his empire to ruling only the northern and central China—and this chance would not come again. Indeed, against Liu Ye's advice, on 23 September 221 he appointed Sun Quan the King of Wu and granted him the [[nine bestowments]].

In 222, at the [[Battle of Xiaoting]], Sun Quan's general [[Lu Xun (Three Kingdoms)|Lu Xun]] dealt Liu Bei a major defeat, stopping the Shu offensive. Shu would not again pose a threat to Sun Quan from that point on. Later that year, when Cao Pi demanded that Sun Quan send his [[crown prince]] [[Sun Deng (Eastern Wu)|Sun Deng]] to the Wei capital [[Luoyang]] as a hostage (to guarantee his loyalty), Sun Quan refused and declared independence (by changing [[Regnal name|era name]]), thus establishing Eastern Wu as an independent state. Cao Pi [[Cao Pi's invasions of Eastern Wu|launched a major attack on Wu]], but after Wei defeats in early 223, it became clear that Wu was secure. After Liu Bei's death later that year, Zhuge Jin's brother [[Zhuge Liang]], the regent for Liu Bei's son and successor [[Liu Shan]], reestablished the alliance with Sun Quan, and the two states would remain allies until Shu's eventual destruction in 263.