Wikipedia
Fanzhen was a governmental system involving administration through regional governors ( jiedushi). The term fanzhen literally means "buffer town", and refers to the system of settling troops in strategic locations along the empire's border areas, which during the Tang dynasty came under the control of provincial military governors, or jiedushi. As control of these fanzhen devolved from central authority into the hands of the local leaders, they at times became powerful enough to threaten the imperial Chinese central government during the Tang dynasty, (618–907 CE) particularly during and after the An Shi Rebellion. This important example of the fanzhen system in action involved the case of An Lushan, the provincial governor and military commander who started this rebellion against Emperor Xuanzong of Tang, in 755 CE. An Lushan went so far as to proclaim himself emperor, in 756 CE; but, was killed by his own son in the following year and Tang power was re-established by 763 CE, when the rebellion was quelled. The An Shi Rebellion allowed many jiedushi on the periphery of the Tang Empire to gain significant autonomy with many became virtual warlords. Subsequent Tang emperors were unsuccessful in curtailing the power of these fanzhen, in particular, Emperor Dezong of Tang (r. 780–805 CE) was driven from his capital, Chang An, after an unsuccessful attempt to subjugate them. Subsequent Emperor Xianzong of Tang (r. 805–820 CE) experienced some success against the fanzhen but at the cost of further empowering the eunuchs who had come to dominate the life of the Imperial Court. Xianzong died in 820 CE, possibly as a result of court intrigue, and his successors were unable to stop the dynasty's decline. The ambitions of the jiedushi, in tandem with the corruption of the Imperial Court eunuchs who dominated the central civil administration and even attained high military command under the later Tang, contributed to the eventual disintegration of the Tang monarchy. A brief resurgence under emperors Wuzong and Xuānzong failed to halt the eventual decline of the dynasty, which collapsed following a further series of revolts that included the Wang Xianzhi and Huang Chao rebellions.
Parallels are evident between the rise of the fanzhen in Tang China and the rise of feudalism in medieval Europe following the decline of the Carolingian Empire.