In East Asia, the medieval period marked the heyday of hybrid dynasties—regimes established by nomadic or semi-nomadic people that combined their own cultural traditions with Chinese political institutions. Our research, which focused on three wall segments located in distinct ecological zones, suggests that each was constructed by one of these hybrid dynasties. That such groups—whose identity was closely tied to mobility—constructed extensive barrier systems remains one of the central enigmas surrounding the "Medieval Wall Systems." The earliest of the three systems is the Northern Line, built by the Liao dynasty (916–1125). The Liao, founded by the Kitan people, controlled vast areas of northern China, southern Siberia, and eastern and central Mongolia. The Eastern Line, including the segment known as the "Mongolian Arc," was built by the Jin dynasty (1115–1234). Founded by the Jurchen people, the Jin originated in Manchuria and conquered both the Liao and extensive territories in central China, including the entire Yellow River basin. The Gobi Line was constructed by the Western Xia dynasty (1038–1227), established by the Tangut people, which ruled over large desert regions in present-day northwestern China and southern Mongolia.