10. Genghis Committed His Greatest Atrocities Against the Western Xia
Genghis had reduced the Western Xia in China to vassalage in 1210, and for nearly a decade, they served him, assisting against the Jin and other enemies. However, when war broke out between Genghis and the Khwarezmians, the Western Xia took the opportunity to renounce their vassalage and ally with the other Chinese. Genghis responded to the betrayal by invading the Western Xia again in 1225, this time with the aim of exterminating them. He conducted a genocidal campaign, in which he systematically reduced and destroyed their cities, while massacring both the urban and rural populations.