In the twenty-fourth year of Jian'an (219), Liu Bei's group entered its heyday, and in the same year, Guan Yu was defeated and died in the battle of Xiangfan, and Liu Bei's power began to flourish and decline.

【Rapid development】

Liu Bei is one of the old princes of the Three Kingdoms period, he has occupied Xuzhou twice earlier, and later although he sent people under the fence, he lived in Jingzhou to serve Liu Biao, but he also got the help of Zhuge Liang and others in Jingzhou, Liu Bei took the opportunity to rise up during Cao Cao's southern expedition, and Sun Quan united, seized Jingzhou, developed rapidly, and became one of the important princes at that time.

Liu Bei's second rise route was mainly Jingzhou-Yizhou-Hanzhong.

In history, Cao Cao's southern expedition to Jingzhou was not only a huge crisis for Liu Bei, but also a huge opportunity, and he took advantage of this opportunity to unite with Sun Quan and make a comeback.

Originally, in terms of Liu Bei's power, there was no capital to form an alliance with Sun Quan, but at that time, the Jiangdong group did not have much choice under the huge pressure of Cao Cao, and in order to fight Cao Cao, they needed to attract all the forces, so they easily let Liu Bei and them reach an alliance, forming an alliance with Sun Quan as the main and Liu Bei as the auxiliary.

After the Sun-Liu coalition army first defeated the invincible Cao Cao in Chibi, and then repelled Cao Ren in Jiangling, Cao Cao's forces withdrew from the south of the Yangtze River, in the capture of Jingzhou, Liu Bei in the name of Liu Biao's eldest son Liu Qi, through the friendship of the landlord to take away all the four counties of Jingnan, and then borrowed Nanjun from Sun Quan with the righteousness of uniting against Cao Cao, plus part of Jiangxia County originally occupied by Liu Qi, Liu Bei's forces have controlled most of the territory of Jingzhou such as the six counties of Jingzhou.

After seizing Jingzhou, Liu Bei quickly set his sights on Yizhou, which was owned by Liu Zhang at that time, and Liu Zhang's weakness was known to the world, so not only Liu Bei was interested in Yizhou, but Sun Quan, Zhou Yu and others' next target was also Yizhou, but Liu Bei on the one hand blocked Sun Quan and Zhou Yu from crusading against Yizhou, on the other hand, he was at odds with Zhang Song, Fa Zheng and others in Yizhou, as a result, Sun Quan and others failed to send troops and gave up halfway, but Liu Bei was invited by Liu Zhang to easily enter Yizhou and help him fight against Zhang Lu.

Liu Zhang invited the wolf into the room, and he didn't feel it when he met in Fucheng, but as Zhang Song was denounced by his brother Zhang Su, Liu Zhang knew what was going on even if he was a fool, so Liu Zhang and Liu Bei officially broke up, and the two sides began to fight in Yizhou.

Liu Bei first used Pang Tong's strategy to kill Yang Huai, Gao Pei and others in Baishui Pass, seize their troops, and then turned south to crusade against Liu Zhang, defeated Zhang Ren, Liu Bi, Leng Bao, Deng Xian, Wu Yi and other generals sent by Liu Zhang in the area of Fuxian, and occupied Fucheng, while Liu Zhang's remnants retreated to Mianzhu, and at the same time Liu Bei transferred Zhuge Liang, Zhang Fei, Zhao Yun and others from Jingzhou to attack Yizhou.

Liu Zhang later sent Li Yandu to lead the generals of Mianzhu, as a result, Li Yan surrendered directly, Mianzhu was lost, after Liu Bei surrounded the city, Zhang Ren and Liu Xuan and others retreated to the city, and Liu Zhang's son Liu Xun struggled to resist, Zhang Ren was defeated and captured, did not surrender and died, the city was surrounded for nearly a year before Liu Bei conquered, Liu Bei was able to enter the army to surround Chengdu. After Zhang Fei and others broke through Jiangzhou, they swept Xichuan with Zhuge Liang and Zhao Yunbing in three ways, Zhao Yun pacified Jiangyang, Qianwei and other counties, and Zhang Fei pacified Ba County and Brazil two counties. In the end, the combined forces surrounded Chengdu and joined Liu Bei.

After Liu Bei besieged Chengdu, he got the submission of the general Ma Chao, Liu Zhang saw that the general trend had gone, and under the persuasion of Liu Bei's envoy Jian Yong and others, he gave up resistance and surrendered out of the city, and Yizhou was captured by Liu Bei.

In the nineteenth year of Jian'an (214), Liu Bei seized Yizhou, and its territory of influence included most of the territory of Jingzhou and Yizhou, which was the largest territory of the entire Shu Han group.

After Liu Bei occupied Yizhou, Cao Cao also captured Hanzhong, in order to avoid his own portal falling into the hands of Cao Cao, Liu Bei sent troops to the Northern Expedition under the persuasion of Fa Zheng and others, the first attack was led by Zhang Fei and Ma Chao, but was repelled by Cao Hong and others, the second time Liu Bei personally led the troops, and only Xiahou Yuan, Zhang He and others were still in Hanzhong, Liu Bei used Xiahou Yuan to rescue Zhang He when he sent Huang Zhong to kill him, and reversed the overall situation in one fell swoop. Liu Feng seized Shangyong and other places, thus occupying Hanzhong.

In the twenty-fourth year of Jian'an (219), shortly after the Battle of Hanzhong, Guan Yu launched the Battle of Xiangfan in Jingzhou, flooding the Seventh Army and shaking China, and the momentum of Liu Bei's group reached its peak.

【The Beginning of Decline】

When Guan Yu flooded the Seventh Army, the prestige of Liu Bei's group and even the Shu Han forces can be said to have reached the highest point in history, but it was at this time that Liu Bei's power began to flourish and decline.

Earlier, the reason why Liu Bei's group was able to develop rapidly was not only because of the efforts of the three armies, but also because Sun Quan attracted most of Cao Cao's firepower for Liu Bei, so that Liu Bei's group had time and space to develop itself, but after Liu Bei became bigger, the relationship with his ally Sun Quan began to drift apart, and the hatred between him and Cao Cao began to get higher and higher, and finally he not only replaced Sun Quan as Cao Cao's first target, but also turned against his allies and was hit by Sun Quan. As a result, Guan Yu did not die on the way to defeat Cao Cao, but his life was lost at the hands of his allies, and Liu Bei completely lost Jingzhou.

It can be said that the importance of Sun Quan to Liu Bei can be understood even by simple addition and subtraction, one less ally and one more enemy, which is an unbearable blow to Liu Bei's ambitions.

The fall of Jingzhou also marked that Liu Bei could no longer achieve the goal of sending troops to the two routes of the "Longzhong Pair", and he was getting farther and farther away from the goal of restoring the Han dynasty and dominating the world.

[Unseizing the opportunity]

In history, if Liu Bei had won over Sun Quan, then when Guan Yu launched the Battle of Xiangfan, Liu Bei's group would have an excellent fighter.

After Guan Yu flooded the Seventh Army and shocked China, if Sun Quan also took the opportunity to go on a northern expedition, and Liu Bei went out of Hanzhong to attack Guanzhong, it would be disastrous for Cao Cao's group, at this time, because Cao Cao's army in the Xiangfan area had been basically taken away by Cao Ren and Yu Ban, and most of them had been captured by Guan Yu, and only a small number were still guarding in Xiangyang and Fancheng, it can be said that there was no support from other places, Cao Ren basically couldn't wait for enough reinforcements, and once Sun Quan sent troops, Guan Yu's original defense of Sun Quan's troops could also be liberated, In this way, the possibility of Guan Yu conquering Xiangfan will be greatly improved.

And Liu Bei's departure from Hanzhong, although it can cause a lot of momentum, but the threat to Cao Cao may not be great, because the earlier battle in Hanzhong has consumed a lot of Yizhou, and Liu Bei no longer has enough capital to launch another large-scale campaign, but as long as Liu Bei sends troops, Cao Cao cannot ignore this, because he has lost Hanzhong and can no longer lose Guanzhong.

For Sun Quan, this is also a great opportunity to seize Hefei, because in the third line, Liu Bei threatened Chang'an, Luoyang, Guan Yu threatened Xuchang, relatively speaking, only Sun Quan had the least threat to Cao Cao, so Zhang Liao and others may get the least support, and Sun Quan after a long period of recuperation, abundant troops, sufficient supplies, in the third line is the strongest, in this case, Sun Quan still can't beat Hefei, just take a piece of tofu to death.

However, the prerequisite for all this is that Sun Quan and Liu Bei are a pair of good friends and allies!