Qin Shi Huang and the Unification of China

Shang Yang, chancellor of Qin under Duke Xiao from 359 to 338 BCE, abolished hereditary aristocratic privilege in Qin and replaced it with a system of ranks earned strictly through military merit, organized the population into groups of five and ten families bound by mutual, collective responsibility for reporting crime (baojia), and reorganized Qin's territory into districts (xian) run by appointed rather than hereditary officials. These reforms, though they eventually cost Shang Yang his own life after the death of his royal protector, gave Qin a decisive military and administrative advantage over its six rival states. Between 230 and 221 BCE, under the young king Ying Zheng and his chancellor Li Si, Qin conquered those rivals one by one, Han in 230 BCE, Zhao in 228 BCE, Wei in 225 BCE, Chu in 223 BCE, Yan in 222 BCE, and finally Qi in 221 BCE, unifying China for the first time under a single ruler.