The Battle of Jiawang was fought between the armies of Cao Cao and Liu Bei in Xu Province in 200 AD. Cao Cao defeated and captured Guan Yu, whom he pressed into his service.
By 200 AD, Cao Cao faced threats on all fronts. His largest rival, Yuan Shao, challenged him for control of northern China, while Liu Bei was a thorn in his side from Xu Province and Gong Du's Yellow Turban remnants threatened Cao Cao's south. Cao Cao himself led an army facing off against Liu Bei, and, while he made preparations for the campaign against Yuan Shao, he decided to strike against Liu Bei first.
Cao Cao and his general Xun Yu attacked Liu Bei's sworn brother Guan Yu at Jiawang, where the two armies met in the local marshland. Cao Cao's catapults pounded Guan Yu's soldiers as they charged into battle, and Cao Cao had his infantry engage Guan Yu's main body as his cavalry swung around Guan Yu's flank to massacre his archers and attack his rear. Guan Yu was trapped and captured while attempting to flee, but he proved willing to join Cao Cao's army, and Cao Cao persuaded him to defect, seeing him as a useful ally against Yuan Shao.