In the Middle Ages the technology of weapon development moved from man power to gun powder. Catapults and other stone throwing artillery would be replaced with cannons. Bows and arrows and crossbows were replaced with hand held guns. These developments helped to end the period of time called the Middle Ages.

English Yew longbow (105 lbf at 32 inches). Photo taken by James Cram.

Genoese archer

Archers and crossbowmen could win battles. The archers could rain down upon the enemy such a lethal amount of arrows so as to stop any successful charge. Archers started their training when they were very young. A long bow required much strength and skill to be used effectively in battle.
Crossbowmen could use their weapons to fire a bolt into an armoured knight thus killing or wounding him. A crossbow was a power weapon that needed a mechanical lever to arm it before it could be fitted with a bolt and fired. The crossbow man did not need the skills the archer had.

 An archer at an arrowslit

 A crossbow man at an arrowslit