Cao Xiu
In 217, Cao Cao's rival Liu Bei launched a campaign to seize control of Hanzhong Commandery, which was guarded by Cao Cao's general Xiahou Yuan. When Liu Bei sent Wu Lan (吳蘭), one of his officers, to lead troops to garrison at Xiabian County (下辯縣; northwest of present-day Cheng County, Gansu), Cao Cao ordered his cousin Cao Hong to lead an army to attack the enemy. Cao Xiu was commissioned as a Cavalry Commandant (騎都尉) to serve as an adviser to Cao Hong. Before they left, Cao Cao told Cao Xiu, "You may be an adviser, but you're actually the commander." When Cao Hong received the order, he delegated his command to Cao Xiu.