During the High and Late Middle Ages: 1) Feudal monarchs increased their power over local lords, helping form European nations. In England, William the Conqueror established a strong central government and common law. 2) Conflicts between monarchs and nobles led to the Magna Carta, which guaranteed noble rights and required the monarch to obey the law. 3) The power of the papacy grew, as popes could crown emperors and excommunicate disobedient monarchs. The Crusades further increased papal and royal authority in Europe.