Han–Xiongnu wars
The Han–Xiongnu wars or Sino–Xiongnu wars, were a series of military conflicts fought from 133 BC to 89 AD between the agrarian Chinese Han dynasty and the nomadic Xiongnu confederacy, although extended conflicts can be traced back as early as 200 BC and as late as 188 AD. The Chinese civilization initially clashed with Inner Asian nomadic tribes (then collectively known as Di) that would later become the Xiongnu during the Warring States period, and various northern states built elongated fortifications (which later became the Great Wall of China) to defend against raids down from the Mongolian Plateau. The unified Qin dynasty, who conquered all other states under Qin Shi Huang, dispatched Meng Tian in 215 BC in a successful campaign to expel the Xiongnu from the Ordos region (which was often used as a staging area to threaten Qin's Guanzhong heartland).