Part 1 of 2: In the course of their pursuit of the fleeing Khwarazmian Amir, Genghis Khan's two top commanders have reached the shores of the Caspian Sea, and heard some of the strangest tales about what - and who - lay beyond. When the Great Khan gives his go-ahead to scout it out, they'll launch a three-year trek that will remake the world in their bloody image. Time Period Covered: 1220-1221 CE