The Liao dynasty, which at its largest covered much of Mongolia, Manchuria, and northern China, was ruled by semi-nomadic and pastoral people, the Qidan. The Liao maintained a dual administration, Qidan and Chinese, and even a prime-ministership, to ensure the survival of their own customs and traditions whilst utilizing the efficiency of Tang structures of government. In 1115, the Qidan were overthrown by another semi-nomadic people, the Ruzhen (Jurchen). With the support of the Northern Song, the Ruzhen took control of the north and founded the Jin dynasty. The Liao were forced westwards to the region of the Tian mountain range in present-day Xinjiang, where they established the Western Liao (1125-1211). The rest of northwest China was dominated by the Western Xia, a Tibetan related people who recognized the Liao as their overlords.