If Zhuge Liang had taken care of his illness instead of the Northern Expedition, the Shu Han might have died long ago, and some people would be surprised. Doesn't that make him stronger? However, I forgot that Cao Wei would be happier if Shu Han did not go north.

Because we can better develop internal affairs and concentrate on dealing with Wu Dong, Zhuge Liang pointed out in "Longzhong Dui" that Cao Cao unified the north, and Liu Bei could only compete with Cao Cao if he cooperated with Wu Dong.

Imagine why before Battle of Red Cliffs, the ministers of Wu Dong wanted to surrender as soon as they heard that Cao Wei was attacking the city. Only a few people such as Zhou Yu and Lu Su are leading troops. Lu Su also pointed out to Sun Quan that if he wants to defeat Cao Cao, he must cooperate with Liu Bei.

Of course, if Soochow can win Jingzhou and Yizhou together and govern the river with Cao Wei, just like the Southern and Northern Dynasties, just like the Southern Song Dynasty and the Jin Dynasty, Lu Su's theory of lying on the couch is this view.

But now, the situation is divided into three parts. There are two states in Cao Wei, thirteen states, nine states in Cao Wei, one state in Shu Han, and less than three states in Soochow. The population of the Three Kingdoms is more than seven million, that of Cao Wei is more than four million, that of Shu Han is only one million, and that of Soochow is only two million.

If Shu Han really stays in Yizhou, then Cao Wei can transfer the large troops stationed in Chang 'an to Hefei, Huainan and Wan to concentrate on dealing with Wu Dong. The population of Cao Wei is twice that of Wu Dong, and with the occupation of the Central Plains, there are many talents. It was only a matter of time before Cao Wei entered Wu Dong.

This means that even though Liu Bei suffered such a big loss after the defeat of Yiling, when Sun Quan came to make peace, Liu Bei immediately agreed, and after Liu Bei's death, Zhuge Liang quickly sent Deng Zhi to Wu Dong to consolidate this alliance with Wu Dong.

Zhuge Liang's second Northern Expedition took advantage of Cao Xiu's crushing defeat in Shi Ting to transfer Cao Wei's army to Huainan, and the two sides agreed to jointly attack Cao Wei. In addition, Zhuge Liang's Northern Expedition had another advantage, that is, it led the war to Wei, slowly encroaching on Wei, and Wudu and two counties were thus captured.