Many people know that the key to the transformation of the Tang Dynasty from prosperity to decline was the "Anshi Rebellion" that occurred in 755 AD, and the root cause of the "Anshi Rebellion" was that Tang Xuanzong granted too much power to An Lushan and others in Fanzhen Jiedu, which prompted him to "hold a sharp weapon in his hand and kill his heart". Later, although the "Anshi Rebellion" was put down, the situation of the division of the Tang Dynasty's feudal towns could no longer be ended, and eventually led to the demise of the Tang Dynasty. So the question is, why did Tang Xuanzong give power to the envoy of Fanzhen Jiedushi?
Some people believe that in his later years, Tang Xuanzong favored his traitors and indulged in beauty, so it led to the secret development and growth of the fan town, so that it caused an irreparable situation. In fact, however, Tang Xuanzong's establishment of the Fanzhen Jiedushi was a major move taken in the early days of his reign, that is, in the "Kaiyuan Prosperous Era", and its original intention was to solve the two major problems that had long plagued the Tang Empire: border troubles and financial crises.
The previous emperors of the Tang Dynasty continued to expand their territory, and by the time of Tang Xuanzong's reign, the territory of the Tang Dynasty was already very vast. However, there are great difficulties, and in the case of inconvenient transportation in ancient times, the defense of the frontier needs to pay a very expensive cost. For example, in the early eighth century, the Tang Dynasty garrison garrison in the west was about 50,000 troops, but the military expenditure of these 50,000 people was even greater than that of more than 100,000 troops in the Gyeonggi region. By 722, the total strength of the empire was about 600,000, most of which were border guards.
Although the Tang Dynasty's border guards were numerous, the efforts that could be made to defend the national border were limited. Because the surrounding forces of the Tang Dynasty were nomadic or semi-nomadic peoples, their armies were highly mobile, and the goal was not to occupy the land, but to plunder grain and population by raid. Most of the border towns were garrisoned with only a few hundred men, which would obviously not be able to cope with if the nomadic cavalry invaded on a large scale. At this time, the central Tang Dynasty had to send a large army and temporarily appoint experienced military commanders to go on a crusade. However, this process is very cumbersome and inefficient, often when the army reaches the border, the enemy has already withdrawn to its own territory and disappeared into the vast grasslands and the Gobi.
In order to solve this problem, from the later years of tang ruizong's (tang xuanzong's father) late in the reign, a long-term envoy was appointed to command the various defense areas. If a defensive zone is attacked, being on the frontier allows for rapid military deployment without the long delays caused by the appointment of field commanders and the mobilization of troops by the imperial court, as in the past.
The effect of decentralization was immediate, and the combat efficiency of the Tang Dynasty border guards under the command of JieDushi was greatly improved. Therefore, after Tang Xuanzong ascended the throne, he successively set up nine envoys in the frontier areas, a total of ten major feudal towns, each of which had a large number of direct subordinate armies (commonly known as the "Jingluo Army"), of which the largest number of troops, Fanyang Jiedu, had more than 90,000 troops. In addition, in order to improve efficiency, the envoy of the clan town was also granted administrative powers, and he could appoint and dismiss officials within the clan town under his jurisdiction.
However, although the establishment of the thrifty envoy has solved the problem of military efficiency, another problem is still very prominent, that is, the long-term financial difficulties. From the founding of the Tang Dynasty, it has always implemented an extensive fiscal policy and insisted on not competing with the people for profits. Therefore, the people of the Tang Dynasty were relatively rich, but the central finances were very tight.
The Tang Dynasty had a huge territory and a large number of soldiers, so logistical support became a big problem. It is a traditional practice to concentrate grain and materials from various places in the Beijing Division, and then transport them from the Beijing Division to the frontier areas in a unified manner, but in the case of inconvenient transportation in ancient times, such round-trip transportation, coupled with the loss along the way, is bound to cause amazing waste. In the "Art of War of Sun Tzu", it is mentioned that "one bell to eat the enemy, twenty bells to me", the implication is that the army only needs to eat "one bell" of grain, but if the central government collects it from the local government and then transports it to the front line, it needs to pay the cost of "twenty bells".
Although the border guards throughout the Tang Dynasty had military tuns and could partially achieve self-sufficiency, the "big head" of military expenditure still depended on the allocation of funds from the imperial court. However, the Treasury of the Tang Dynasty was not abundant, and it was difficult to bear such a huge expenditure. In order to achieve efficient management and operation, Tang Xuanzong decided to further decentralize power and entrust the financial power of the area under the jurisdiction of the fanzhen to the envoy of Jiedu, so that he could realize his own profit and loss. In this way, after mastering the military and administrative powers, jiedushi further grasped the financial power, and the town became an independent kingdom of jiedushi.
Tang Xuanzong set up the Jiedu Envoy in order to solve two major problems, but what he did not expect was that decades later, the Jiedu Envoy became the biggest problem for all Tang emperors since him. It can be seen that how to deal with the problem is the real problem that everyone facing the dilemma should really think about.
References: Old Book of Tang, New Book of Tang, Zizhi Tongjian