Ordos Plateau
In Chinese accounts, the Xiongnu first appear at Ordos in the "Yizhoushu" and "Shanhaijing" during the Warring States period before it was occupied by Qin and Zhao. It is generally thought to be their homeland, however when exactly they came to occupy the region is unclear, and it might have been much earlier than traditionally thought, as suggested by archaeological finds. As the Xiongnu expanded southward into Yuezhi territory around 160 BC under their leader Modun, the Yuezhi in turn defeated the Sakas (Scythians) and pushed them away at the Issyk Kul. It is thought the Xiongnu also occupied the Ordos area during the same period, when they came in direct contact with the Chinese. From there, the Xiongnu conducted numerous devastating raids into Chinese territory (167, 158, 142, 129 BC). The Han Dynasty started to fight the Xiongnu in the 2nd century BC under emperor Han Wudi, and colonized the area of the Ordos under Shuofang commandery in 127 BC. Prior to the campaign, there were already commanderies established earlier by Qin and Zhao until they were overrun by the Xiongnu in 209 BC.
Modu Chanyu
Modu ruled from 209 BCE to 174 BCE. He was a military leader under his father Touman, and later Chanyu of the Xiongnu, centred in modern-day Mongolia. He secured the throne and established a powerful Xiongnu Empire by successfully unifying the tribes of the Mongolian-Manchurian grassland in response to the crisis of the loss of Xiongnu pasture lands to invading Qin forces commanded by Meng Tian in 215 BCE. While Modu rode and then furthered the wave of militarization and effectively centralized Xiongnu power, the Qin quickly fell into disarray with the death of the first emperor in 210, leaving Modu a free hand to expand his Xiongnu Empire into one of the largest of his time. The eastern border stretched as far as the Liao River, the western borders of the empire reached the Pamir Mountains, whilst the northern border reached Lake Baikal.