Before the establishment of the Tang Dynasty, the central government set up a garrison, a city, a town and an army on the border, which was generally called Dao. In the second year of Jing Yun, Tang Ruizong (AD 7 1 1), Hebai Yansi was the governor of Liangzhou (now Wuwei City, Gansu Province). In order to prevent the invasion of Tubo, Hexi buffer region became the first buffer region in the Tang Dynasty. When Emperor Xuanzong of the Tang Dynasty began to set up a large number of buffer regions. During the Tianbao period of Xuanzong in Tang Dynasty, it increased to 10: Hexi, Fanyang, Longyou, Jiannan, Anxi, Shuofang, Hedong, Beiting, Pinglu and Lingnan. With the establishment of the border buffer zone, the system of officers and men was gradually replaced by the system of recruiting soldiers, and a large number of elite soldiers appeared in the border areas, with 490 thousand foot soldiers and 80 thousand war horses stationed in the border areas.

After the historical rebellion broke out, in order to resist the rebel attack, the military town system was extended to the mainland. The most important States set up our military envoys to direct the military affairs of several States; Less important States set up national defense envoys or regimental ambassadors to guard military positions. Therefore, in today's Shaanxi, Shaanxi, Henan, Anhui, Shandong, Jiangsu, Hubei and other places, there are many large and small military towns, such as our troops, national defense envoys and Yingyong. Later, it was extended to the whole country. These are all military posts, but our envoys are often named as observation and disposal ambassadors (renamed from previous interviews), and observation and disposal ambassadors are also named as defense ambassadors or regimental ambassadors. They all become local military and political chiefs and are power institutions at or above the state level. In the late Tang dynasty, the so-called buffer town, also known as the square town, was formed by being frugal and prudent.