Eastern Wu (东吴) was the southern kingdom of the Three Kingdoms period. Sun Quan declared himself king in 222 and emperor in 229. Wu outlasted both Cao Wei and Shu Han and was only brought down by the Jin dynasty’s invasion in 280.
Foundation
The Sun family’s power in the south was built by Sun Jian and Sun Ce, then consolidated by Sun Quan. The Battle of Red Cliffs (208) — won with Liu Bei’s forces and Zhou Yu’s command — stopped Cao Cao’s push south and secured the Yangtze as the border. Sun Quan’s court moved to Jianye (modern Nanjing), and the state developed a strong navy and riverine warfare capability.
Relations with Wei and Shu
Wu alternated between alliance and conflict with Shu. The alliance at Red Cliffs gave way to rivalry over Jing Province; Guan Yu’s death and the Battle of Yiling (222) left the two states in a tense equilibrium. With Wei (and later Jin) to the north, Wu relied on the Yangtze and on capable generals such as Lu Xun and Lu Kang to defend the border.
Fall
After the fall of Shu in 263 and the establishment of the Jin dynasty in 266, Wu was the last of the three kingdoms. Under Sun Hao, the court grew unstable. In 280, Jin forces crossed the Yangtze in strength; Sun Hao surrendered, and Eastern Wu came to an end. The reunification of China under Jin marked the close of the Three Kingdoms period.