Modu Chanyu in the context of "Xiongnu"

Qin Shi Huang (Chinese: 秦始皇, Qín Shǐ Huáng, pronunciation; February 259 – 12 July 210 BC) was the founder of the Qin dynasty and the first emperor of China. Rather than maintain the title of "king" (wáng 王) borne by the previous Shang and Zhou rulers, he assumed the invented title of "emperor" (huángdì 皇帝), which would see continuous use by monarchs in China for the next two millennia.

Born in Handan, the capital of Zhao, as Ying Zheng (嬴政) or Zhao Zheng (趙政), his parents were King Zhuangxiang of Qin and Lady Zhao. The wealthy merchant Lü Buwei assisted him in succeeding his father as the king of Qin, after which he became King Zheng of Qin (秦王政). By 221 BC, he had conquered all the other warring states and unified all of China, and he ascended the throne as China's first emperor. During his reign, his generals greatly expanded the size of the Chinese state: campaigns south of Chu permanently added the Yue lands of Hunan and Guangdong to the Sinosphere, and campaigns in Inner Asia conquered the Ordos Plateau from the nomadic Xiongnu, although the Xiongnu later rallied under Modu Chanyu.

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 Empire 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) to defend against raids down from the Mongolian Plateau. The unified Qin dynasty, who conquered all other states under Emperor Qin Shi Huang, dispatched General 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). However, the subsequent civil wars following the Qin dynasty's collapse gave the Xiongnu tribes, who were then unified into a large confederacy under Modu Chanyu, the opportunity to reinvade the Ordos region. After the Han dynasty was established in 202 BC, Emperor Gao tried to fight off Xiongnu invasions but had himself trapped in an ambush during the Battle of Baideng, and a truce was negotiated by bribing Modu's wife, thus ending first Han–Xiongnu War. Decades of de jure peace then followed with the Chinese gifting "harmony via marriage" to appease the Xiongnu, who still routinely raided Chinese borderlands.

The Han-Zhao (simplified Chinese: 汉赵; traditional Chinese: 漢趙; pinyin: Hàn Zhào; 304–329 AD), or Former Zhao (simplified Chinese: 前赵; traditional Chinese: 前趙; pinyin: Qián Zhào), was a dynastic state of China ruled by the Liu (Luandi) clan of Chuge-Xiongnu ethnicity during the Sixteen Kingdoms period of Chinese history. In Chinese historiography, it was given two conditional state titles, the Northern Han (北漢; Běi Hàn) for the state proclaimed in 304 by Liu Yuan, and the Former Zhao (前趙; Qián Zhào) for the state proclaimed in 319 by Liu Yao. The reference to them as separate states can be misleading, given that when Liu Yao changed the name of the state from "Han" to "Zhao" in 319, he treated the state as having been continuous from when Liu Yuan founded it in 304; instead, he de-established his imperial lineage from the Han dynasty and claimed ancestry directly from Modu Chanyu.

The reason it is also referred to as "Former Zhao" in historiography is to distinguish it from the Later Zhao founded by Shi Le in 319, which was also known officially as "Zhao". Since both the Former Zhao and Northern Han were ruled by the same family, Chinese scholars often conditionally combined them into a single Han-Zhao regime. Numerous Western texts refer to the two states separately; others referred to the Han state as the "Northern Han" (not to be confused with Northern Han of the Five Dynasties and Ten Kingdoms period).

Heqin, also known as marriage alliance, refers to the historical practice of Chinese monarchs marrying princesses—usually members of minor branches of the ruling family—to rulers of neighboring states. It was often adopted as an appeasement strategy with an enemy state that was too powerful to defeat on the battlefield. The policy was not always effective. It implied an equal diplomatic status between the two monarchs. As a result, it was controversial and had many critics.

Lou Jing, the author of the policy, proposed granting the eldest daughter of Emperor Gaozu of Han to Modu Chanyu of the Xiongnu. His proposal was adopted and implemented with a treaty in 198 BC, following the Battle of Baideng two years prior. Wang Zhaojun, of the Han dynasty, and Princess Wencheng, of the Tang dynasty, are among the most famous heqin princesses.