the power of the Donghu people of eastern Mongolia and Manchuria as well as the Yuezhi in the Hexi Corridor of Gansu, where his son, Jizhu, made a skull cup out of the Yuezhi king. Modu also retook the original homeland of Xiongnu on the Yellow River, which had previously been taken by the Qin general Meng Tian. Under Modu's leadership, the Xiongnu became so strong that they began to threaten the Han dynasty. In 200 BC, Modu besieged the Chinese Han Dynasty emperor Gaozu (Gao-Di) with his 320,000-strong army at Peteng Fortress in Baideng (present-day Datong, Shanxi) almost causing Emperor Gaozu, the first Han emperor, to lose his throne in 200 BC. Gaozu (Gao-Di) after agreed to all Modu's terms, such as ceding the northern provinces to the Xiongnu and paying annual taxes, he was allowed to leave the siege. Although Gaozu was able to return to his capital Chang'an (present-day Xi'an), Modu occasionally threatened the Han's northern frontier and finally in 198 BC, a peace treaty was finally settled. Xiongnu in their expansion drove their western neighbour Yuezhi from the Hexi Corridor in year 176 BC, killing the Yuezhi king and asserting their presence in the Western Regions. By the time of Modu's death in 174 BC, the Xiongnu were recognized as the most prominent of the nomads bordering the Chinese Han empire According to the Book of Han, later quoted in Duan Chengshi's ninth-century Miscellaneous Morsels from Youyang: Xiongnu hierarchy The ruler of the Xiongnu was called the Chanyu. Under him were the Tuqi Kings. The Tuqi King of the Left was normally the heir presumptive. Next lower in the hierarchy came more officials in pairs of left and right: the guli, the army commanders, the great governors, the danghu and the gudu. Beneath them came the commanders of detachments of one thousand, of one hundred, and of ten men. This nation of nomads, a people on the march, was organized like an army. After Modu, later leaders formed a dualistic system of political organisation with the left and right branches of the Xiongnu divided on a regional basis. The chanyu or shanyu, a ruler equivalent to the Emperor of China, exercised direct authority over the central territory. Longcheng (龍城) became the annual meeting place and served as the Xiongnu capital. The ruins of Longcheng were found south of Ulziit District, Arkhangai Province in 2017. North of