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.
Army of the Han dynasty
In 71 BC, Chang Hui and two other generals led a force of 100,000 to aid the Wusun against the Xiongnu. The majority of the forces failed to find any Xiongnu, but Chang Hui successfully aided the Wusun in defeating a Xiongnu invasion. However the Xiongnu came back in winter and took many captives. On the way back across the Altai Mountains, the Xiongnu suffered heavy casualties from a sudden blizzard, devastating their army. The next year the Xiongnu were attacked on all sides by Wusun, Wuhuan, and the Han. One third of all Xiongnu died.