Zhang Liao
In 207, Zhang Liao followed Cao Cao on a campaign against Yuan Shang, who had allied with the Wuhuan tribes in northern China. When Cao Cao was preparing to attack the enemy in Liucheng (柳城; present-day Xingcheng, Liaoning), Zhang Liao warned him that Jing Province's Governor Liu Biao take advantage of his absence from Xu to send Liu Bei to attack Xu and take control of the capital. However, Cao Cao felt that Liu Biao would not send Liu Bei to attack Xu because he did not trust Liu Bei, so he proceeded with the campaign against Yuan Shang and the Wuhuan. When they encountered the enemy, Zhang Liao displayed great fervour and strongly urged Cao Cao to launch an attack. Cao Cao was so impressed with Zhang Liao that he passed him his personal signal flag. Zhang Liao led the assault on the Wuhuan at White Wolf Mountain (白狼山; near present-day Lingyuan, Liaoning), defeated them and executed the Wuhuan chieftain Tadun.