At the end of the Eastern Han Dynasty, Dong Zhuo rebelled and held the son of heaven hostage. After being killed by Lu Bu, Stuart Wang Yun did not pardon his subordinates, such as Li Jue and Guo Si, and forced them to rebel again. Two men hijacked the son of heaven and all their minions were rewarded. Under the alienation of loyal ministers, the two men fought, one took the son of heaven and the other took the official, and were injured in many battles. Under the protection of Yang Feng and other generals, the emperor took the opportunity to take off, so he sent someone to Cao Cao for help, thinking that he was a loyal minister. At this time, Cao Cao's advisers advised him to rescue. In particular, Yu Xun was the most active. He pointed out to Cao Cao the future strategic policy of "welcoming the emperor instead of being a minister" (euphemistically, of course). Advise Cao Cao to join the army as soon as possible and control the son of heaven in order to gain the political initiative, and emphasize that if he doesn't take it today, the son of heaven will fall into the hands of others one day. After listening to their words, Cao Cao set out, with cavalry first and infantry following, and sent an army himself. The practice proved that his practice was not only correct, but also decisive, because Yuan Shao, the biggest warlord in the north, also moved this idea, but he was too indecisive and too late. When Li Jue and Guo Si saw that they had escaped from the emperor, they reconciled and pursued. However, after the coach was frustrated, Tian Zi successfully met Cao Cao's troops. Under the hospitality of Cao Cao, Tian Zi, who was hungry, was naturally grateful to him and greatly raised him. However, Cao Cao persuaded the son of heaven to move to Xu county on the grounds that the capital was burned down by thieves and the son of heaven had to obey because of Cao Cao's military power. Cao Cao's real purpose is that Xu county is his base camp, where he will be able to better control the son of heaven in his hands. Later, every time Cao Cao fought or rewarded or punished, he could use the name of the son of heaven, which could be described as a "famous teacher" and "clear reward and punishment" Moreover, in the name of the army of the son of heaven, many counselors and military commanders gathered to submit, and the people on the land he attacked were more obedient. For example, he used to let Liu Bei beat Yuan Shu under the guise of imperial edict, so that they could kill each other and consume each other's strength, and later he was vulnerable. This is holding the emperor as a minister.