In twenty-five years, the Mongol army subjugated more lands and people than the Romans had conquered in four hundred years. Genghis Khan, together with his sons and grandsons, conquered the most densely populated civilizations of the thirteenth century. Whether measured by the total number of people defeated, the sum of the countries annexed, or by the total area occupied, Genghis Khan conquered more than twice as much as any other man in history.