 At the beginning of the Han dynasty (206 BC – AD 220), the region was subservient to the Xiongnu, a powerful nomadic people based in modern Mongolia.The Xiongnu were a tribal confederation of nomadic peoples who, according to ancient Chinese sources, inhabited the eastern Eurasian Steppe from the 3rd century BC to the late 1st century AD.Chinese sources report that Modu Chanyu, the supreme leader after 209 BC, founded the Xiongnu Empire.