Surveillance commissioners (guanchashi 觀察處, full title guancha chuzhi shi 觀察處置使 "surveillance and supervisory commissioner") were high military officials dispatched for temporary duties. The office was used during the Tang period 唐 (618-907). In 706 Emperor Zhongzong 唐中宗 (r. 683-684, 705-709) decided to dispatch touring surveillance commissioners (xunchashi 巡察使) to ten important circuits. They were on duty for two years, and then exchanged by new commissioners. In 711 the same was done by using the title surveillance commissioners (anchashi 按察使). In 733 their number was raised to fifteen, and their title changed to investigation commissioners (caifangshi 採訪使). Their duties were similar to that of regional inspectors (cishi 刺史), investigating the accuracy of local administration.
In the course of time their rights expanded. In the mid-8th century, when a large number of military commissioners (jiedushi 節度使) were appointed on a more permanent basis, these were concurrently given the title and the rights of surveillance commissioners. After the end of the rebellion of An Lushan 安祿山, military commissioners or defense commissioners (fangyushi 防御使) were appointed throughout the empire. The latter, in rank lower than the military commissioners, where often concurrently investigation commissioners, and thus unifying military with civilian jurisdiction in one hand. In 758 the title of investigation commissioner (caifangshi) was officially changed to surveillance commissioner (guanchashi).
While the offices of defense commissioner and military training commissioner (tuanlianshi 團練使) were concurrently carried out by regional inspectors, the surveillance commissioners were concurrently chief defense commissioners (du fangyushi 都防御使) and chief military training commissioners (du tuanlianshi 都團練使). The surveillance commissioners had no own emblem or flag, signifying that their status was lower than that of the military commissioners.
During the late Tang period the whole empire was divided into fourty-odd circuits, the larger of them encompassing ten or more prefectures and governed by military commissioners, the smaller ones having a size of two or three prefectures and governed by surveillance commissioners. In the very late phase of the Tang period some surveillance commissioners refused to cooperate with the central government and adopted the title of military commissioner.
The Song dynasty 宋 (960-1279) appointed surveillance commissioners for each prefecture, but this was but a temporary office and often enough just endowed with a salary (rank 5B, a so-called salaried-only office, jiluguan 寄祿官, or vain title, xuxian 虛銜) without any real duties.
The Liao 遼 (907-1125) and Jin 金 (1115-1234) empires also made use of the title for officials in a somewhat lower position than the military commissioners. The Yuan dynasty 元 (1279-1368) abolished it. It was used again for a short time in the early Ming period 明 (1368-1644) and the early Republican era (1912-1949).