Liu Bei was defeated by Cao Cao in Xuzhou, and was separated from Guan Yu, Zhang Fei and Zhao Yun, so he joined Yuan Shao. At the same time, Guan Yu and Cao Cao about three things, what to protect Liu Bei's family, what to surrender Han not Cao, mainly the last one, know Liu Bei to go, immediately after the flash. You do not say, Cao Cao really agreed.