Since Liu Bei left Jingzhou to seize Xichuan, he handed Jingzhou over to Guan Yu. Jingzhou is equivalent to the place where Liu Bei started, and most of the people in Liu Bei Group are also from Jingzhou. Such an important position was given to Guan Yu, not only because of his high ability and prestige, but also because of Guan Yu's position in Liu Bei's heart. Zhang Fei, both brothers, did not hand over Hanzhong to Zhang Fei after Liu Bei captured it, but let Zhang Fei guard Langzhong. According to this, many people think that Zhang Fei's position in Liu Bei's heart is not very important, so he is left idle in Langzhong. In fact, this understanding is wrong. Liu Guan and Zhang Taoyuan became sworn brothers. The relationship is no longer a simple relationship between monarch and minister, but as close as brothers. Liu Bei left Langzhong to Zhang Fei precisely because of its strategic position and importance, and sometimes even surpassed Hanzhong. If Liu Bei doesn't give it to Zhang Fei, who can he give it to? So this is a great trust, not an idle one.

First, although Langzhong is not close to the front line of the Shu-Wei War, its strategic position is extremely important. The road from Langzhong can go directly to Hanzhong, and the advance can quickly reinforce Hanzhong, and the retreat can be used as the second line of defense for defending Shu. By water from Langzhong, you can reach Jiangzhou downstream, and from Jiangzhou to the east, you can stop Wu Dong's attack. Another point is that Langzhong is also very close to Chengdu. In case of any accident in Chengdu, Zhang Fei can lead the army to Chengdu at the first time. Such a hinterland connecting all directions of Shu, I think Liu Bei can't think of a second person except Zhang Fei. With Zhang Fei guarding Langzhong, Liu Bei probably slept soundly.

Secondly, the terrain in Langzhong also determines its position is very important. Shu Han is located in Sichuan, with many mountains and rivers. There is a huge mountain barrier in central and northern Sichuan, which consists of Jianmen Mountain and Daba Mountain range, thus separating Yizhou from the north. There are only two entrances to this pass, one is Jinniu Road and the other is Micang Road. Jinniu Road on the side of Jianmen Mountain is the main road between Yizhou and the outside world. Micang Road is on the side of Daba Mountain, and Langzhong is on the side of Micang Road, which is the hub of Micang Road. It can be said that after holding Jiange and Langzhong, the foreign enemy could not attack Yizhou. Because Micang Road is a short walking road, it can achieve the purpose of surprise attack in the case of sudden war, so the importance of Langzhong even exceeds Jiange.

Third, Zhang Fei is a famous soldier in the Three Kingdoms. Leaving Zhang Fei in Langzhong can also exert great pressure on the Longyou area of Cao Wei, making Cao Wei afraid to attack Hanzhong easily. At the same time, we can send troops to harass the Wudu and Yinping areas of Cao Wei, and constantly reduce the pressure of Cao Wei on Yizhou.

Langzhong has a long history and has always been the political, economic, military and cultural center of northern Sichuan. It is the second largest capital of Shu Han after Chengdu. Liu Bei can only give such an important place to the most trusted Zhang Feilai.

From the above analysis, we can know the importance of Langzhong. Liu Bei chose Zhang Fei to guard Langzhong, just as Guan Yu guarded Jingzhou, because they were the people Liu Bei trusted most. With Zhang Fei guarding Langzhong, Yizhou is foolproof. Of course, Zhang Fei did not only engage in military affairs in Langzhong, but also made great achievements in economy and culture. For example, Zhang Fei beef, a well-known snack in Sichuan, has long been not only a business card in Langzhong, but also a cultural business card in Sichuan, which has also promoted economic development.