Externally, the Han Dynasty also faced the same threat that plagued every indigenous Chinese government throughout history—the danger of raids by the nomadic peoples of the steppes. To the north and west, China borders on desert and range-lands that have been controlled by various nomadic peoples over time, including the Uighurs, the Kazakhs, the Mongols, the Jurchens (Manchu), and the Xiongnu.
The nomadic people had control over the extremely valuable Silk Road trade routes, vital to the success of most Chinese governments. During prosperous times, the settled agricultural people of China would simply pay tribute to troublesome nomads, or hire them to provide protection from the other tribes. Emperors even offered Chinese princesses as brides to the "barbarian" rulers in order to preserve the peace. The Han government, however, did not have the resources to buy off all of the nomads.