Genghis Khan adopted a policy of strategic marriages. He would marry off a daughter to the king of an allied nation. The king’s other wives were dismissed. Then he would assign his new son-in-law to military duty in the Mongol wars, while the daughter took over the rule of the kingdom. Most sons-in-law died in combat.

In this way Genghis Khan built a shield around the Mongol homelands, while expanding beyond them. In his marital instructions to his daughter Alaqai, “He left no doubt that this was a major military assignment. She was not there merely to administer, but to rule — thereby beginning the expansion of the Mongols from a tribal nation into a global empire.”

By the time of Genghis Khan’s death, his daughters ruled from the Yellow Sea to the Caspian. Probably never before, or since, have women held so much power over so vast a region.