I'm guessing "overcoming difficult barriers"
Answer:
The Xiongnu were a group of people that differed a lot from the Chinese people. Since the Chinese considered the people that are not Chinese as barbarians, the Xiongnu were classified as such based on numerous things. Unlike the Chinese that were settled, the Xiongnu largely practiced nomadic lifestyle. The Xiongnu also had large beards, which was not a trait of the Chinese society nor was something seen as nice. While China was involved in agriculture, the Xiongnu were involved in herding animals. The physical appearance also differed, as the Xiongnu are believed to have been a mixture of Mongol, Turkic, and Caucasian people, thus making them look much different in general than the Chinese people.
Explanation:
Not mine, but I hoped this helped
