Complex sentence: Horseback archery also required a different method of riding the horse-with both hands occupied with bow and arrow, horses were trained to respond to commands from the legs of the rider as well as the reins.
Split into simpler sentences: Horseback archery also required a different method of riding the horse, namely with both hands occupied by bow and arrow. Horses were trained to respond to commands from the legs of the rider as well as the reins.