The Battle of the Yanran Mountains in 89 CE was a fateful event in the history of both the ancient China and the Roman Empire. The allied army under the command of the Han general Dou Xian (d. 92) inflicted a major defeat on the Northern Xiongnu, effectively ending their political fortunes. The defeated Northern Xiongnu were pushed westward. After a lengthy (and still insufficiently understood) movement across much of the Eurasian continent, they reached the fourth-century Eastern Europe, setting in motion the Age of Migrations there, which brought about Germanic incursions into the Roman heartland and the eventual collapse of the Western Roman Empire.