As China approached the end of the nineteenth century, it was ravaged by rebellions, warlords, and famines, while the Imperial government had done little to ease the suffering of the common folk. This ancient kingdom had collided with Western intruders and was plunged into wars with foreign powers as well as domestic political violence. In the coming century, hundreds of millions would be slaughtered, starved, tortured, raped, forced into slave labor, or persecuted on political and religious grounds. Crimes against humanity, including genocide and war crimes, accounted for many of the deaths and atrocities. Other than a few Japanese war criminals, culprits—including state and nonstate forces, warlords, rebels, and foreign invaders—have not been scrutinized for their responsibility in such crimes.

The Boxer Rebellion: 1898–1901

Two deadly episodes preceded...