The Tang Dynasty
During the Tang Dynasty, beacon towers stood every 10, 15, 20 or 50 kilometers and protected today’s Xinjiang. The beacon towers system during the Tang had two parts: towers were in charge of watching and warning, while another type of building, the Pu (or station), were used to transfer official documents. The soldiers were recruited from local areas instead of the Central Plains far away. The Tang abandoned the complicated beacon fire system of the Han and added a new coding system to avoid fire messages from being decoded.