Battle of Fancheng and the Death of Guan Yu
Liu Bei’s general Guan Yu besieged Wei-held Fancheng and drowned its relief army, but Wu’s Lü Meng meanwhile seized Jing Province behind him. Guan Yu was captured and killed, and the Shu–Wu alliance broke.

Shang Xi · Public domain · Source
In 219 Guan Yu advanced north from Jing Province and besieged Fancheng, held by Cao Ren. Heavy rains flooded the Han River, and the seven armies of Yu Jin’s relief force were drowned and surrendered, shaking the north. But Sun Quan, who coveted Jing, sent Lü Meng to strike Guan Yu’s rear; cut off, Guan Yu was captured near Maicheng and executed early in 220. The loss of Jing was a heavy blow to Shu and led to Liu Bei’s campaign against Wu at Yiling.