First, social chaos. This war has brought unprecedented disaster to society. "Biography of Guo Ziyi in Old Tang Dynasty" records: "The Palace Que was burned, and there was no one in ten miles, and everything was abandoned, and there was no rafter. There are less than 1000 households in the central area, and the scenery in Jingyi (should be changed to hazelnut) is the number of jackal houses. It lacks both military reserves and manpower. East to Zheng, Bian and Xufang, north to Qin and Huai, it is a place isolated from human population, a thousand miles of depression ",including almost the whole middle and lower reaches of the Yellow River, and it is desolate. Du Fu said in a poem: "After the lonely Tianbao, there are more than 100 homes in my garden, and there are many things in the world." This shows that after the war, the broad masses of people were homeless.
Second, the separatist regime of the buffer region. The Anshi Rebellion destroyed the ruling foundation, weakened the feudal centralization, created the necessary conditions for the feudal separatist regime, and made the Tang Dynasty from prosperity to decline. Since then, in fact, the unified central dynasty's control over the local area has weakened, and Anshiyu has been lifted.
At the end of the Tang dynasty, the party established a separatist regime in the north. When Shi Chaoyi, the son of Shi Siming, was defeated in Yecheng, General Pugu Huai 'en of Tiele of the Tang Dynasty pursued him. Pugu had contradictions with the Tang Dynasty. In order to form a clique, he intends to preserve the strength of Anshi's old men, let them continue to control Hebei, and make the Anshi's old general Tian captured by (now southern Hebei and northern Henan), Zhang Zhongzhi (later renamed Li) and Li Huaixian. This is the so-called "three towns in Hebei". The three towns gradually integrated local military, political and economic forces. Later, other regions, such as Ziqing (now Zichuan and Yidu, Shandong Province), Li Lingyao in Xuanwu (now Kaifeng and Shangqiu, Henan Province) and Li Xilie in Huaixi, became independent and refused to accept the management of the imperial court. Some of these towns have their own officials, and they don't lose the palace, and some don't pay tribute to the court. They even arrogantly claimed to be kings and emperors, contradicting the Tang Dynasty until its demise. This phenomenon is not over.
Third, exploitation has intensified. Due to the war, the labor force is seriously insufficient, and the ruling class has to increase taxes, which makes the class oppression and the oppression of the ruling class even deeper. Therefore, the contradiction between peasants and local classes became more and more acute, and finally forced peasants to rebel in the process of dispatching troops, which formed the climax of peasant uprising in the middle of Tang Dynasty. After the Anshi Rebellion, the number of registered permanent residence held by the state was greatly reduced. Within a few hundred miles between Tongguan and Hulao Pass, there are only "more than a thousand households", and Fangcheng County in Dengzhou has plummeted from more than 10,000 households in Natural Forest Protection to less than 200 households. The government imposed the burden on farmers who are still registered in the household registration. During the Yuan and Meng Dynasties in Tang Xianzong, due to the impassability of government decrees, taxes could only be collected from eight southeast provinces (western Zhejiang, eastern Zhejiang, Xuanhua, Huainan, Jiangxi, Hubei, Fujian and Hunan). People under the rule of Fangzhen also suffered from "heavy punishment and heavy taxes", such as Tian's "heavy taxes" in Weibo Town and Li's "material losses" in Bianzhou. The exorbitant taxes and levies imposed by the Tang government and the provinces finally aroused the peasants' constant armed rebellion. During Zong Yi's reign, rebellions took place all over the country, including Yuan Chao rebellion in the first year of Baoying (AD 762), Qing rebellion in western Zhejiang in the same year, Zhangdu rebellion in Suzhou and Changzhou in the same period, Yang Zhao rebellion in Zhou Shu and Yongtai rebellion (AD 765). Although these rebellions were quickly suppressed, they further weakened the strength of the Tang Dynasty.
Fourth, the frontier is unstable. After the Anshi Rebellion, the Tang Dynasty also lost control of the surrounding ethnic minorities. Together with the Anshi Rebellion, the Tang Dynasty deployed heavy troops to the mainland in Longyou, Hexi and Shuofang areas, which led to the emptiness of border defense. The western Tubo people took the opportunity to enter, and the Longyou and Hexi corridors were exhausted. The Tang Dynasty still controlled the Anxi North Court in the Western Regions. A few decades later, around 790 AD, the Tang Dynasty lost the Anxi North Court in the Western Regions. From then on, the Tang dynasty was in a precarious state, and it was even more precarious.
Fifth, the economic center of gravity moved south. The Anshi Rebellion prompted the northern people to move southward in the history of China, and further moved the economic center southward. The Anshi Rebellion caused great damage to northern production, and a large number of northerners crossed south. The south is relatively stable, and the migration of the population in the north has brought a large number of labor and advanced production technology, which has promoted the economic development in the south of the Yangtze River. The economy in the south is increasingly surpassing that in the north, and the economy in the north and south tends to be balanced.
Sixth, the independence of the western regions. Around 753, it was the heyday of the Tang dynasty's governance of the western regions, but since then, with the drastic changes in the domestic political situation, the power of the Tang dynasty in the western regions has also dropped sharply, from the peak to the trough. In 755 (the 14th year of Tianbao), the famous Anshi Rebellion broke out in the Tang Dynasty. The Northeast Frontier Rebels, led by barbarian generals An Lushan and Shi Siming, went south and captured the eastern and western parts of Beijing. Tang Xuanzong fled Chang 'an and went south to Sichuan Basin. After Xuanzong's son Su Zong succeeded Lingwu, he mobilized Qin Wang's northwest border guards to counter the rebellion, and a large number of border soldiers under Anxi and Beiting, who were guarding the western regions, were also transferred to the mainland.
In 756 (to the end of Yuan Zai), three western regions of Tang Jun were transferred back to the mainland, including 5,000 troops led by Li and Duan, 7,000 troops led by Li Sima and 3,000 troops led by Ma Phosphorus. Fifteen thousand people from the three armed forces returned to Fengxiang to participate in the war to recover Chang 'an. Later, on this basis, the Town Northwest Pavilion Camp with strong fighting capacity was formed.
In addition to the border troops in the western regions, the Tang Dynasty also recruited local troops from various countries in the western regions to help counter the rebellion. It is clearly recorded that Wang Weichisheng led 5,000 domestic soldiers and horses. In addition, countries such as big food sent troops with Khan. At the latest, before the first month of 757 (the second year of Germany), they had already marched into Hexi area. In the autumn of 758 (the first year), Tuhuoluo Ye Huwu and the leaders of the nine western countries came to the DPRK, demanding that they "help the country and seek thieves", and the Soviet Union sent them to the Shuofang camp to handle affairs. A large number of border soldiers in the western regions were transferred internally, which played an important role in quelling the Anshi Rebellion, but greatly weakened the influence of the Tang Dynasty in the western regions.
At this time, the external threats of the western regions were mainly big food and Tubo, and the decline of the defense ability of the western regions provided them with opportunities for invasion. However, the big food forces did not take the opportunity to move eastward, but sent troops to help Tang Ping rebel, which shows that the big food has no intention (or no ability) to enter the area east of Qingji from the beginning. For Tubo, at this time, the Tang Dynasty not only withdrew the border guards from Anxi and Beiting, but also deployed troops from Longyou and Hexi to guard against Tubo. It is much more convenient and beneficial to invade Longyou and Hexi than to attack Xicheng, so Tubo attacked Hexi on a large scale. In this situation, the western regions were preserved and fought alone for nearly half a century.
By 763 (the first year of Guangde), the Tubo army had captured Lanzhou, Kuo, Hehe, DuDu, Fujian, Qin, Cheng and Wei, and occupied most of Hexi and Longyou [29]. Since then, the defenders of the western regions have cut off contact with the mainland, but they still serve Tang Zhengshuo and stick to the western regions. There is the title of Guangde four years (equivalent to 766 years). In fact, Guangde only lasted for two years (763-764), and in 765, it was changed to Yuan Yongtai (765-766). The gaoyao epitaph unearthed in Turpan still uses the Guangde year number, which means that we lost contact 765 years ago. I wonder if Chang 'an was changed to Yongtai. The four towns still maintain a certain strength at this time. Around 765 (the first year of Yongtai), Tang Jun in Hexi couldn't resist the Tubo attack and sent envoys to four towns to ask for 10,000 reinforcements in Hexi, which at least showed that the situation in the western regions was much more stable than that in Hexi.
Around 768 (the third year of Dali), the defenders of the western regions resumed contact with the imperial court. People in the ruling and opposition parties were moved by their spirit of "selfless service to the country". Tang Daizong wrote a letter of commendation, informed Tang Jun about the situation in the mainland and praised the defenders.
In fact, as far as the original dynasty is concerned, the management of the western regions is nothing more than internal and external causes. Internally, controlling the western regions can not only publicize the national prestige, but also ensure the prosperity of the Silk Road trade. Externally, controlling the western regions can contain and weaken the nomadic forces in the north, further ensure the security of Hexi and Longyou, and prevent the nomadic forces in the north and the south from merging. After the Tubo captured Guanlong, it went deep into the confidant area of the Tang Dynasty, and the western regions lost their original strategic significance. The survival of the western regions is of little practical significance to the entire border defense of the Tang Dynasty. Therefore, although the western regions have the intention of "serving the country faithfully", the imperial court has to take the attitude of letting it die, because things are not as good as sympathy.