When Genghis Khan dropped down on the cities of Khwarizm, he commanded an army of about 100,000 to 125,000 horsemen, supplemented by Uighur and other Turkic allies, a corps of Chinese doctors, and engineers for a total of 150,000 to 200,000 men. By comparison, the Khwarizm ruler had some 400,000 men under arms across his empire, and they were fighting with the home advantage on their own territory.
