Knighthood, Orders of. Knights of the Middle Ages banded themselves together in groups called orders. They vowed loyalty to their king or lord and formed a military organization to defend his land against enemies. During the Crusades, orders of knighthood fought the Muslims in the Holy Land. The knights who joined these orders took religious vows to live as monks as well as loyal fighting brothers. The most famous of the religious orders were the Knights Hospitallers, the Knights Templars, and the Teutonic Knights.