English: Emperor Wu repeatedly sent troops across the frontier to fight the Hsiung-nu. After many campaogns, he finally defeated them, conquering the land west of the Yellow River, and established four commanderies there: Wu-wei, Chang-yeh, Chiu-ch'uan and Tun-huang. Apart from sending settlers into the frontier land, he also built beacon structures and post stations all over the North and Northwest, and stationed soldiers in these regions to guard the border and engage in farming. Aside from frontier horsemen, troops guarding Chu-yen also included garrison soldiers, pioneers and criminals from interior prefectures.