Climate Shocks, Dynastic Cycles, and Nomadic Conquests: Evidence from Historical China

Nomadic conquests have helped to shape world history, yet we know little about why they occurred. Using climate and dynastic data from historical China since 221 BCE, this study finds that the likelihood of nomadic conquest increased with less rainfall proxied by drought disasters, which drove pastoral nomads to attack agrarian Chinese for survival. Moreover, consistent with the dynastic cycle hypothesis, the likelihood of China being conquered increased when a Chinese dynasty was established earlier (and hence was weaker, on average) than a rival nomadic regime. These results survive a variety of robustness checks, including using the latitude of the Sino-nomadic border as an alternative dependent variable. The dynastic cycle effect also persists in an extension to world history. The effects of other climate shocks, such as snow, frost, and temperature anomaly, are not robust.