Genghis Khan, unlike most Mongols in history, is a household name, regularly misappropriated as a right-wing totem. If we recall the genocidal killing sprees of, say, Stalin and Mao, perhaps it would be more historically accurate to say ‘to the left of Genghis Khan’. In the popular imagination he is the despot’s despot, a one-man killing machine who led his army of mounted archers to triumph after triumph, terrorising and slaughtering by the million to carve out an empire that stretched from the Caspian to the Pacific.