 He protected these new lands by raising earthen walls along their northern border, close to what is now Hohhot in Inner Mongolia.Garrisons and forts were also placed at strategic spots within the new territory, such as Yanmen Pass between the northern plains and the Hutuo Valley.In the mid-3rd century, the Yanmen governor Li Mu, relocated there under the command of Handan used these interior defenses and drills the commandery's citizens to minimalize casualties to good effect when he lured more than 100,000 Xiongnu horsemen into the heart of the commandery before defeating them with 160,000 chariots, cavalry, and archers.