Why was Genghis Kahn able to conquer the asian steppes? What role did the stirrup play?
Genghis Khan was able to conquer a wide area, because of his armys equipment advantages and training. He also had two outstanding generals, Jebei Noyan (Prince Arrow) and Subotai "the Valiant", that turned the wars in his favor. The following information is taken from notes by a friend of Michael Van Biesbrouck, a trainer in the SCA (Society for Creative Anachronism).
He organized the Mongols into units of 10,000 men each basic unit used high wooden saddles and stirrups, which allowed them to shoot in any direction. They also had composite bow (70-160 lbs) with thumb rings, which could kill at 300 yards with max range >600 yards. The addition of the thumb ring allowed a sharper release of the bow, which increased the range and velocity of their arrows, although it required greater experience and practice.
Archers carried 2 - 4 bows, with 60-400 arrows of various types (long and short distance, limb cutters etc) depending on length of campaign (and what book you're reading). Army replacements were often just told to find the army and report for duty, even with the army over 2000 miles away. Troops often traveled over 60 miles a day.
Note on Mongol tactics The Mongols would often wipe out entire cities, especially if they had rebelled to use as examples for others.
To read more visit: http://www4.gvsu.edu/triert/archery/history.htm