China's first imperial dynasty was the Qin dynasty (221–207 BCE). The Qin united the Chinese Warring States by conquest, but their regime became unstable after the death of the first emperor Qin Shi Huang. Within four years, the dynasty's authority had collapsed in the face of rebellion.

After the third and last Qin ruler, Ziying, unconditionally surrendered to rebel forces in 206 BCE, the former Qin Empire was divided by rebel leader Xiang Yu into the Eighteen Kingdoms, which were ruled by various rebel leaders and surrendered Qin generals. A civil war soon broke out, most prominently between two major contending powers – Xiang Yu's Western Chu and Liu Bang's Han.