Fanzhen -

"Fanzhen, also called fangzhen, was a governmental system involving administration through regional governors (jiedushi). The term fanzhen literally means "buffer town", and refers to the strategic settlement of troops in locations along the empire's border areas. During the Tang dynasty, these settlements came under the control of provincial military commissioners, otherwise known as jiedushi. During the late Tang period, the phenomenon of fanzhen domination has been termed fanzhen geju by historians. - Wikipedia"