 The Qin created a national system of military garrisons on a three-tier administrative hierarchy as a practical measure to control the population according to strict legalistic principles.The Qin soon lost power in a revolt and were replaced by the Han dynasty, who continued many aspects the Qin system of imperial administration, including its system of laws.At its inception, the Han dynasty was immediately faced with the task of rebuilding the urban infrastructure which had been destroyed by Qin dynasty purges and the war of succession after its downfall.