Xiongnu
The Xiongnu () were a confederation of nomadic peoples who, according to ancient Chinese sources, inhabited the eastern Asian 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.
Han–Xiongnu War
During the spring of 123 BC, General Wei Qing set off to Mongolia with an army to attack the Xiongnu; they marched back victorious to Dingxiang. Two months later, the Han army advanced towards the Xiongnu again, but this time the Xiongnu were prepared for the invasion by the Han forces. However, hereafter, due to the military expeditions that the Han empire undertook, the Xiongnu moved their capital and retreated to the far northern regions of the Gobi Desert.