In the sixteenth year of Jian'an (211), Cao Cao sent Xiahou Yuan, Zhong Xuan and others to crusade against Hanzhong, Liu Zhang was greatly frightened when he knew it, so he listened to Zhang Song's advice to unite Liu Bei to fight against Cao Cao, and finally led Liu Bei into Sichuan.

【Lianbei Anti-Cao】

After Cao Cao went south to occupy Jingzhou in the thirteenth year of Jian'an (208), Liu Zhang began to change his attitude towards the imperial court, and successively sent Yin Pu, Zhang Su, Zhang Song and others to visit Cao Cao, but did not get a satisfactory reply, especially when Zhang Song visited Cao Cao, when Cao Cao had pacified Jingzhou and killed Liu Bei, he simply did not appoint Zhang Song, and Zhang Song naturally harbored resentment. As a result, Cao Cao's army was defeated in Chibi soon after, and many people died due to the plague.

After Zhang Song returned, he tried his best to slander Cao Cao and persuaded Liu Zhang to take the initiative to sever contact with Cao Cao. He said to Liu Zhang: "Liu Yuzhou is a brother of the clan with you, and you can form an alliance with him. Liu Zhang had already sent an envoy for the third time at that time, and he had exhausted his patience, and when he heard Zhang Song say this, of course he thought it was, so he gave up uniting with Cao Cao and turned to win over Liu Bei, who was from the same sect.

There is a similar record in the "Spring and Autumn Period of the Book of Han", it is said that when Zhang Song went to see Cao Cao, Cao Cao was arrogantly boasting about himself, and he didn't pay attention to Zhang Song at all, and he didn't even give Zhang Song an official position. After Zhang Song returned, he persuaded Liu Zhang to sever relations with Cao Cao.

It can be said that Liu Zhang took the initiative to come to Cao Cao three times, the first time Cao Cao only gave Liu Zhang the fourth rank of General Zhenwei, but Liu Zhang's brother Liu Mao was crowned as the third rank of General Pingkou, the second time Cao Cao sealed the envoy Zhang Su's official, did not say anything to Liu Zhang, and the third time there was nothing at all. In fact, Liu Zhang was rejected by Cao Cao and pushed alive to his opponent Liu Bei.

If Cao Cao took the opportunity to stabilize Liu Zhang in history, even if he could not lay a good foundation for the later attack on Yizhou, at least he would not let Liu Zhang fall to Liu Bei's side, so that Liu Zhang would lead the wolf into the house in the future and let Liu Bei seize Yizhou. In history, Liu Bei was able to capture Yizhou, and Cao Cao did not say that he had half of the credit, but at least one-third of the credit.

The famous historian Xi Chiaoya of the Eastern Jin Dynasty also commented on this matter: Xi Qi Huan rebelled against the Nine Kingdoms with his merits, Cao Cao temporarily took advantage of his arrogance and divided the world into three points, and he was diligent in decades and abandoned it in the middle of the pitch, don't you hesitate! It is a gentleman who is humble and humble, considers the following people, and lives in order to make it high, and respects it and keeps it humble. Love is close to things, so although it is expensive, people do not tire of it; Deqia is a group of people, so the industry is wide and the world is more and more happy. Fu Ran, so he can have his wealth, protect his merits, and show his glory at that time, and spread the blessings of a hundred generations, how arrogant and reserved! The gentleman is the one who knows that Cao Cao can't take over the world.

【Lure the Wolf into the Room】

Liu Zhang, at Zhang Song's suggestion, finally decided to break with Cao Cao and win over Liu Bei instead, so he sent Fa Zheng and Meng Da to help Liu Bei.

Fa Zheng, the word filial piety, Fufeng Yi (now Xiaofayi Town, Meixian County, Shaanxi Province) people. Meng Da, the word Zijing, was changed to Zidu after evading it, and Fa is the same township.

In the early years of Jian'an, there was a famine in the world, Fa Zheng and Meng Da entered Shu together to attach themselves to Liu Zhang, and it took a long time before he was appointed as the commander of Xindu County, and later he was called to Chengdu to act as the military lieutenant. Fa Zheng was not reused, and was slandered by the people of the same county who lived in Shu, saying that he was of bad character, so Fa Zheng felt very unwilling.

However, at that time, Zhang Song, a driver in Yizhou, was very friendly with Fa Zheng, and Zhang Song secretly thought that he would not do anything with Liu Zhang, and often sighed secretly. After Zhang Song sent an envoy to Jingzhou to see Cao Cao's return to Shu, he persuaded Liu Zhang to sever relations with Cao Cao and form an alliance with Liu Bei. Liu Zhang asked, "Who can go for the envoy?" Zhang Song then recommended Fa Zheng, Fa Zheng resigned, and finally reluctantly accepted the order to go to Jingzhou. At that time, Fa Zheng and Meng Da sent thousands of soldiers to help Liu Bei resist Cao's army, and finally Liu Bei and others won the victory, Cao Ren returned to the north, and Fa Zheng completed his mission and returned. After Fa Zheng came back, he praised Liu Bei to Zhang Song for his great talent, so the two conspired and agreed to support Liu Bei together, but they couldn't find the opportunity for a while.

In the sixteenth year of Jian'an (211), Liu Zhang, the pastor of Yizhou, heard that Cao Cao would send Zhong Xuan and others to lead an army to Hanzhong to defeat Zhang Lu, and he was very frightened. Hanzhong is the gateway to Yizhou, and once Cao Cao occupies Hanzhong, he can attack Yizhou south at any time, so Liu Zhang is very worried. Seeing this opportunity, Zhang Song took the opportunity to persuade Liu Zhang: "Cao Cao's army is strong and invincible in the world, if he captures Zhang Lu's territory and then uses his materials, grain and grass to attack Shu, no one will be able to resist him!" ”

Liu Zhang said: "I am worried about this matter, but I can't do anything. Zhang Song said: "Liu Yuzhou is the same clan as you, and Cao Cao is an enemy, he is good at using troops, if he is invited to attack Zhang Lu, Zhang Lu will be defeated, Zhang Lu is defeated, then Yizhou's strength will increase, even if Cao Cao comes in person, I can't help me." ”

According to the record in "The Biography of Liu Zhang", Zhang Song also said at that time: "Now the generals Pang Xi, Li Yi and others in the state are proud of their achievements and have different aspirations, if they can't get Liu Yuzhou's help, Yizhou will be attacked by strong enemies outside, and harassed by chaotic people inside, and will definitely be defeated." ”

Liu Zhang was finally persuaded by Zhang Song and prepared to welcome Liu Bei into Sichuan. However, this matter caused a great controversy within Yizhou, when Liu Zhang's chief secretary Huang Quan advised: "Liu Bei, the general of Zuo, has a reputation for bravery, and now he is invited to Shu, and if you want to treat him with the courtesy of your subordinates, you will not be able to satisfy his wishes; If you want to treat him as a guest, you can't tolerate two kings in one kingdom. If the guest has the stability of Mount Tai, the host will be in danger of being tired. Now we can hold the border and wait for the situation to stabilize. Liu Zhang didn't listen, but instead released Huang Quan as the chief of Guanghan. Liu Zhang's Guanghan Wang Lei hung himself upside down on the gate of the state city to admonish Liu Zhang, Liu Zhang also refused to accept it, and instructed Liu Bei to entertain Liu Bei wherever he went, so that Liu Bei's entry into Yizhou was like returning to his hometown.

According to the record of "The Legend of the Lingling Ancestors", Liu Ba also admonished at that time: "Liu Bei is brave, and letting him enter Yizhou will inevitably cause disaster, so he can't be invited in." After Liu Bei entered Yizhou, Liu Ba said to Liu Zhang: "If Liu Bei is allowed to crusade against Zhang Lu, it is equivalent to releasing the tiger into the mountains and forests." But Liu Zhang did not listen to Liu Ba's advice, and Liu Ba had no choice but to complain behind closed doors.

In history, Liu Zhang's army was average, and even the rebellious Zhang Lu could not be pacified, and there were many troubles within Liu Zhang's group at that time, so in the face of Cao Cao's strong pressure, Liu Zhang finally chose to listen to Zhang Song's advice to lead Liu Bei into Sichuan, and sent Fa Zheng to meet Liu Bei again.

At that time, Fa Zheng led 4,000 troops to Jingzhou to welcome Liu Bei, and bribed hundreds of millions of gifts before and after. Fa Zhengyu took the opportunity to state to Liu Bei the strategy of seizing Yizhou.

After Fa Zheng relayed Liu Zhang's intentions to Liu Bei, he privately offered advice to Liu Bei and said: "With the general's talent, take advantage of Liu Zhang's cowardice; Zhang Song, a capable talent in the state, let him be an internal response in Chengdu; Then the general took advantage of the wealth of Yizhou and the dangerous terrain of the land of abundance, and it was really easy to achieve hegemony under such conditions. Liu Bei then followed Fazheng's strategy to enter Sichuan and seek Yizhou.