南北朝

For two hundred years there were two Chinas. In the south, a succession of short Han-Chinese dynasties ruled from Jiankang on the Yangtze — Song, Qi, Liang, Chen — each founded by a general who overthrew the last. In the north, the Xianbei and other steppe peoples ruled the old heartland from Pingcheng and then Luoyang, and slowly, deliberately, turned themselves Chinese.

The northern courts are the stranger and more brutal of the two. The Northern Wei operated a rule called zigui musi — when a prince was named heir, his mother was put to death, so that no dowager could ever govern. It worked until it produced a woman determined enough to break it, at which point it destroyed the dynasty.

The Northern Zhou empresses ended almost uniformly the same way: five living empresses at once, and then, within a few years, all of them shaven-headed nuns.