[Source] Chapter 17 of "Romance of the Three Kingdoms."
[Explanation] Cutting off hair as a substitute for beheading. This idiom metaphorically means setting an example through one's own actions and demonstrating integrity.
[Historical Anecdote]
At the end of the Eastern Han Dynasty, Cao Cao sought to unify the Central Plains and realize his political ambitions. He recruited soldiers, stockpiled grain, and went to great lengths to attract talented individuals.
Cao Cao had two strategists under him: Mao Jie and Xun Yu. One day, they offered Cao Cao two suggestions. First, he should use the emperor's authority to command the feudal lords, a strategy known as "Holding the Emperor Hostage to Command the Vassals." Second, he should emphasize agriculture, open up wastelands for farming, and amass large grain reserves. Cao Cao found these suggestions very reasonable and accepted them. After careful planning, he began to implement them.
First, he located Emperor Xian of Han, personally paid his respects, brought the emperor to Xuchang, and appointed himself General-in-Chief, thus initiating his strategy of "Holding the Emperor Hostage to Command the Vassals."
After successfully implementing the first measure, Cao Cao was greatly pleased, and the morale of his troops was high. He then began implementing the second measure to solve the food supply problem. He ordered officials to draft and promulgate the "Tuntian Decree" (a policy of military agricultural colonies), and simultaneously commanded his army to extensively open up wastelands and establish military farms. He strictly ordered his soldiers to protect crops and forbade them from trampling on seedlings. Anyone who violated this order would be punished according to military law.
Once, during the wheat harvest season, Cao Cao led his troops on a campaign. The mission was urgent, and the army marched quickly. The common people, fearing the troops, kept their distance and dared not harvest their crops. Upon learning this, Cao Cao issued a military order: any soldier who trampled on wheat fields would be immediately beheaded and displayed as a warning, assuring the local people they had nothing to fear. The soldiers carefully walked through the wheat fields. As Cao Cao rode his horse, a bird suddenly flew out from the wheat field, passing right over the head of Cao Cao's horse. Startled, the warhorse reared up, neighing and charging into the adjacent wheat field. When Cao Cao finally reined the horse to a stop and looked down, he saw that a large area of wheat had been trampled.
Cao Cao immediately dismounted and said to the official in charge of military law: "My horse has damaged the wheat, violating the prohibition. I request that I be punished according to military law." The official replied, "General, as the supreme commander of the army, how can you be punished?" Cao Cao insisted, "I myself established this law. If I violate it and go unpunished, how can I command the respect of my troops?" The official responded again, "Nobles cannot be subjected to physical punishment. You are the supreme commander of the army, and besides, damaging the wheat was not intentional but an accident. I think there is no need to punish you." After a brief moment of contemplation, Cao Cao said, "Since that is the case, I will temporarily be spared the death penalty. However, having made a mistake, I should still be punished!" With that, he removed his hat, used his sword to cut off a lock of his hair, and threw it forcefully to the ground, declaring, "Let cutting my hair stand in place of beheading."
The story of Cao Cao cutting his hair to uphold military discipline quickly spread throughout the entire army. From the highest commanders to the lowest soldiers, everyone held him in awe and strictly obeyed the military orders, with not a single person daring to violate them. At that time, in Xuchang, Cao Cao's agricultural colony base, soldiers and civilians jointly developed agriculture and protected crops, gradually restoring and developing agricultural production that had been devastated by war. This laid a solid economic foundation for Cao Cao to defeat his rivals and unify northern China.