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Battle of Fancheng (219–220)

In the autumn of 219, Cao Cao ordered Yu Jin to lead seven armies to reinforce Cao Ren, who was under siege by Guan Yu at Fancheng. However, due to heavy rains, the Han River burst its banks and the seven armies were destroyed in the flood. Guan Yu captured Yu Jin, executed his subordinate Pang De, and continued to press on the attack on Cao Ren. Cao Cao ordered Xu Huang to lead another army to help Cao Ren. At the same time, Cao Cao also contemplated relocating the imperial capital from Xuchang further north into Hebei to avoid Guan Yu, but Sima Yi and Jiang Ji told him that Sun Quan would become restless when he heard of Guan Yu's victory. They suggested to Cao Cao to ally with Sun Quan and enlist his help in hindering Guan Yu's advances. In return, Cao Cao would recognise the legitimacy of Sun Quan's claim over the territories in Jiangdong. In this way, the siege on Fancheng would automatically be lifted. Cao Cao heeded their suggestion.

Cao Cao arrived in Luoyang early in the winter of 219 after returning from campaign in Hanzhong. He later led an army from Luoyang to relieve Cao Ren, but turned back before reaching his destination upon receiving news that Xu Huang had defeated Guan Yu and lifted the siege on Fancheng. In the spring of 220, Cao Cao returned to Luoyang and remained there. In the meantime, Sun Quan had sent his general Lü Meng and others to launch a stealth assault on Liu territories in Jing Province while Guan Yu was on the Fancheng campaign, and they succeeded in conquering Guan Yu's key bases in Gong'an County and Jiangling County. Guan Yu, having lost his bases and forced to withdraw from Fancheng, was eventually surrounded by Sun Quan's forces and captured in an ambush and executed. Sun Quan sent Guan Yu's head to Cao Cao, who arranged a noble's funeral for Guan Yu and had his head buried with full honours.