Answer:
By building the Great Wall
Step-by-step explanation:
The Xiongnu were nomadic pastoral people who formed a great tribe and dominated Central Asia for more than 500 years. China were against them and believed that they were a threat, because of that they built the Chinese Wall. The Empire stretched from Korea to the East, Lake Balkash to the West, Lake Baikal to the North and Tibet to the South. They lasted from 214 BC to 350 AD.