Battle of Fancheng
Between November 219 and February 220, Liu Bei's ally Sun Quan broke the Sun–Liu alliance and ordered his general Lü Meng to lead a stealth invasion of Liu Bei's territories in Jing Province while Guan Yu was away at the Battle of Fancheng. After failing to take Fancheng, Guan Yu returned to Jing Province only to find out that Lü Meng had conquered his key bases in Gong'an County and Nan Commandery (南郡; around present-day Jingzhou, Hubei). While attempting to retreat to Yi Province to join Liu Bei, Guan Yu was captured in an ambush and executed by Sun Quan's forces.