The earliest armies of the ancient age used chariots to conduct high speed attacks during battle.  Chariots, however, were expensive, hard to maintain, and useless on broken terrain.  The Mounted Archer proved to be a much more effective means of providing mobile firepower.    Skilled horse-archers like the Mongols were able to strike with terrifying speed and melt away before an effective defense could be mounted.  Riding tough long-haired ponies, the Mongols were able to cover hilly ground quickly and blaze across the plains of Asia with relentless speed. 