English: In order to effectively support the defence of frontier fortresses with quick communications, as well as warning and commands signals, the Han dynasty built roads and established post stations between the interior prefectures and principalities and the northwestern frontier fortresses. Furthermore, the imperial Minister of Finance to the frontier fortresses. Garrison soldiers and their families were separated by thousands of miles and wrote frequently to each other. Much information from government orders to mundane details of personal lives can be found in the wooden slips.