Why did Taizong divide China into 10 inspection circuits?

The Taizong emperor divided China into 10 inspection circuits to provide the central government with an additional means of maintaining standardized and efficient local administration.1

These circuits were not permanent administrative units; rather, they served as regions for occasional inspection tours conducted by special commissioners, who were often members of the censorate sent out from the capital. By implementing this system, Taizong sought to ensure that local prefectures and counties—which were staffed by a unified bureaucracy—adhered to centrally codified laws and procedures. This oversight helped the central government monitor local governance and maintain order across the empire.1