What area does Hexi Corridor refer to, and why did all previous dynasties attach great importance to its control and defense?

Hexi Corridor is a famous road in the history of China, and it is the gateway from the mainland to the western regions. It has important strategic significance and plays an important role in economic integration. Hexi Corridor, which refers to more than a dozen cities in Gansu today, has been weakened today, but all dynasties in history have attached great importance to its control and defense.

There was a real experience about Hexi Corridor in the history of Tang Dynasty. Since the Anshi Rebellion, the area west of the upper reaches of the Yellow River has been occupied by Tubo, and border conflicts often occur. Tubo once captured more than 10,000 people from the Central Plains and enslaved them in their tribes. The captured people bid farewell to their parents' hometown, hundreds of them cried bitterly, and many others jumped off the cliff. What I'm talking about here is that Tubo robbed the African Union.

Further, the Hexi Corridor has been in operation for hundreds of years, from Liu Che and Xuan Di, the Emperor Wu of Han Dynasty, to Yang Dixi's tour, and then to the prosperous Tang Dynasty. Gansu and the Guanzhong mainland established a solid connection, supported each other economically, and had close cultural exchanges. Marriage also made the blood relationship closer. Some ethnic groups who live together "speak Chinese together", and some even change into Hu clothes and demand "naturalization".

The four counties of Dunhuang, Jiuquan, Zhangye and Wuwei in Hexi Corridor have also become international trade metropolises, reflecting the confidence and ability of the imperial court to open its doors to operate the western regions and promote prosperity through mutual exchanges.

In the late Tang Dynasty, the imperial court lost this place because of the Anshi Rebellion. At that time, Tubo took advantage of the rebellion to attack the Tang Dynasty on a large scale, plundering counties and cities and hurting local Han people. Later, they successively occupied Liangzhou, Ganzhou, Shazhou and other places, and Longxi and Hexi became the world of Tubo people.

In the Northern Song Dynasty, there was an action to recover Hehuang, the purpose of which was to recover Hehuang, so that Xixia was attacked between Scylla and Charybdis, and finally to destroy Xixia and unify the northwest. The reformists headed by Wang Anshi won support. Sadly, after Wang Anshi stepped down, Sima Guang came to power, because the military operations in Hehuang area consumed huge human and financial resources of the Northern Song Dynasty court, and the Tibetan rebellion made the Northern Song Dynasty court very passive. In fact, the Song Dynasty wanted to give up these places voluntarily. ? Later, Sima Guang listened to other people's opinions and did not give up Hehuang, but four strategic locations, such as Mizhi, were still given to Xixia, which seriously damaged the national defense interests of the Song Dynasty, and problems emerged one after another. Later, this was one of the reasons for the demise of the Northern Song Dynasty.

The gain and loss of a place is related to the safety of a country, which shows its importance.