Background - XuzhouEdit
When Cao Cao ordered Emperor Xian to order Liu Bei to attack Yuan Shu (Liu Bei was loyal to the Emperor and thus would listen to his command), Liu Bei ordered Zhang Fei to guard Xuzhou. After when Liu Bei and Guan Yu left to attack Yuan Shu, Zhang Fei did not listen to his adivisor's advise not to drink wine. Zhang Fei ordered each person to drink wine, when it was Cao Bao's turn to drink, he refused. Zhang Fei then ordered Cao Bao to be taken out to be beaten 50 times and even said 'Good! Beating you up is like beating up Lü Bu. Zhang Fei did not realise he made a mistake. Cao Bao, who was Lü Bu's son-in-law contacted Lü Bu to invade Xuzhou. Zhang Fei who was so drunk from drinking wine did not realise Xuzhou was under attack. Zhang Fei managed to escape from Xuzhou and headed toward Liu Bei.
Meanwhile, Liu Bei who was camped near Yuan Shu's fortress fighting Ji Ling's troops (More later)