Yanmen Pass
The Zhou state of Jin pushed sporadically northward through both invasions and bribery of the Di's ruling class until its disintegration at the end of the Spring and Autumn Period. King Yong (posthumously known as the "Wuling" or "Martial-&amp;-Numinous King") of the Jin successor state of Zhao adopted nomad-style clothing, equipment, and cavalry tactics in 307BC; in campaigns in 306 and 304BC overran the Loufan ( "Lóufán") and "forest nomads" ( "Línhú") of the Hutuo Valley and the lands to the northwest of the Yanmen Pass, opening up to the Eurasian steppe. He organized these conquests together with Zhao-held Dai as the three commanderies of Yunzhong, Yanmen, and Dai. He protected them by erecting long earthen barricades along what is now considered the Outer Great Wall, as well as a fortress overlooking Yanmen Pass in present-day Dai County. The town of Guangwu, southwest of present-day Shangguan, was established under the Zhao as well.