Forged by Modu around 209 BCE, the Xiongnu were the first great nomad confederation of the eastern steppe — and formidable enough to force the newly unified Han dynasty to ship silk, grain, and imperial princesses northward as tribute to keep the peace. The costly Han campaigns that eventually broke the confederation helped open the Silk Road and strained the empire that won. The Xiongnu set the template — chanyu, dual wings, marriage diplomacy — that the Göktürks and Mongols would inherit. Their language, ethnicity, and possible link to Attila's Huns remain contested; almost all we know of them comes from Chinese sources.
Around 200 BCE the founder of China's Han dynasty rode out to crush a band of northern horsemen and was trapped instead, surrounded on a frozen hilltop for seven days until he bought his way free. The horsemen were the Xiongnu, the first great empire of the eastern steppe, and that humiliation set the terms for two hundred years. To keep them quiet, China sent imperial princesses north as brides and shipped wagonloads of silk as tribute, and along the frontier it manned and extended the walls that would grow into the Great Wall. When China finally turned to war, the campaigns ran so deep and cost so much that the effort helped open the Silk Road and nearly bankrupted the empire that won. The steppe power that made an empire build a wall is known almost entirely through the words of the people who feared it.