After Cao Cao occupied Hanzhong, his ministers advised him to attack Shu, because Liu Bei had just got the territory, and his heart was still unstable and he had a good chance of winning. But Cao Cao said that people should not be too greedy. "The people are not living well, but they are rich and prosperous, and they hope to see evil in Shu!" He means, as long as you get Hanzhong, don't go to Shu. But if he had attacked Yizhou at that time, Liu Bei would probably have been unable to keep it. So Cao Cao missed an opportunity to unify the whole country. The idiom "Long queues looking at Shu" has also spread to this day, and it is used to describe people who are insatiable.

People often think that after Battle of Red Cliffs, the world will be a three-legged situation. In fact, after Battle of Red Cliffs, Yizhou, west of Liu Bei, had Liu Zhang, and Hanzhong, north of Liu Zhang, had Zhang Lu. In the seventh year of Battle of Red Cliffs, Cao Cao conquered Hanzhong, but Zhang Lu knew he couldn't beat him and surrendered. Cao Cao easily got the strategic location of Hanzhong, which is close to Yizhou.

At that time, Liu Bei just caught Liu Zhang's consanguineous clan Yizhou. However, people's hearts have not fully joined. Sima Yi and Ye Liu, under Cao Cao's command, told Cao Cao that it was very appropriate to attack Yizhou. Because Liu Bei has just captured Yizhou, his heart is unstable and his foundation is not deep. If he goes to World War I, he is likely to make great progress again.

However, Cao Cao thought it was too rash and that people should not be too greedy, so he said that he wanted to look forward to the dragon and refused the advice of the counselor. Since ancient times, many people think that Cao Cao's decision is wrong. If he goes after Liu Bei, he will probably destroy Wu Dong downstream, thus unifying the whole country.