Cao Cao's appreciation of Guan Yu is not only meritocratic, but also because they have a long history. As early as the 18th Route Warlord conquered Dong Zhuo, Guan Yu stood up and killed Hua Xiong. Later, he repelled Lu Bu with Zhang Fei and Liu Bei, and his character was very loyal, which was the most appreciated by Cao Cao. If Guan Yu can be brought to his own camp, it will be a blow to Liu Bei and a very good example for people.

First, Cao Cao didn't have much chance to get in touch with Guan Yu alone, but he realized that people like Guan Yu would become their nemesis if they followed Liu Bei. It is only because Liu Bei made a fortune late and didn't have a particularly good opportunity that he ran around. So when Liu Bei joins Cao Cao's camp, Cao Cao will tell him that only you and I are contemporary heroes. Later, Liu Bei fled back to Xuzhou, which also verified his ambition not to live under others for a long time. The best way to disintegrate Liu Bei is to let his brother turn back and make him an army of one man.

Second, Guan Yu is a man of his word. Cao Cao used the opportunity of hunting to test the bottom line of the emperor and even his ministers. Guan Yu wanted to rush out and slay Cao Cao. Later, Guan Yu had to live in Cao Cao's camp for Liu Bei's wife, and he also made it clear that he would not surrender to Cao Cao. If he knows the news of Liu Bei, he will certainly listen to these words without cheating. Even Cao Cao felt very admired. If he is so polite to Guan Yu, he will also give a good one to those who are capable.

Third, although Guan Yu rode thousands of miles alone, killed six generals and took refuge in Liu Bei, which made Cao Cao suffer a little, in the long run, his practice not only gained more talents, but also stabilized people's hearts. Especially when Cao Cao suffered a crushing defeat in Battle of Red Cliffs and fled Huarong Road, Guan Yu also let him live because of his kindness in those years, which was the result of his reciprocated.