During the ninth and tenth centuries the church came under the control of kings and feudal lords, who chose priests, bishops, abbots, and other church officials in their territories, granting them fiefs that provided an income and expecting loyalty and service in return. Church offices were sometimes sold outright — a practice called simony. Although the Roman Church encouraged clerical celibacy, many priests were married or living with women. Wealthy Roman families chose popes from among their members; thus popes paid more attention to their families’ political fortunes or their own pleasures than to the church’s institutional or spiritual health. Not surprisingly, clergy at all levels who had bought their positions or had been granted them for political reasons provided little spiritual guidance and were rarely models of high moral standards.

Serious efforts to reform the church began in the eleventh century. A series of popes believed that secular or lay control over the church was largely responsible for the lack of moral leadership, so they proclaimed the church independent from secular rulers. The Lateran Council of 1059 decreed that the authority and power to elect the pope rested solely in the college of cardinals, a special group of priests from the major churches in and around Rome. The college retains that power today.

Pope Gregory VII (pontificate 1073–1085) vigorously championed reform and the expansion of papal power. He ordered all priests to give up their wives and children or face dismissal, invalidated the ordination of church officials who had purchased their offices, and placed nuns under firmer control of male authorities. He believed that the pope, as the successor of Saint Peter, was the vicar of God on earth and that papal orders were the orders of God. He emphasized the political authority of the papacy, ordering that any church official selected or appointed by a layperson should be deposed, and any layperson, including rulers, who appointed a church official should be excommunicated — cut off from the sacraments and the Christian community.

European rulers immediately protested this restriction of their power, and the strongest reaction came from Henry IV, the ruler of Germany who later became the Holy Roman emperor. Henry continued to appoint officials, and Gregory responded by excommunicating bishops who supported Henry and threatening to depose him. In January 1077 Henry arrived at the pope’s residence in Canossa in northern Italy and, according to a letter later sent by Gregory to his German allies, stood outside in the snow for three days seeking forgiveness. Gregory readmitted the emperor into the Christian community. Although Henry bowed before the pope, he actually won a victory, maintaining authority over his subjects and in 1084 being crowned emperor. This victory was temporary, however, for high nobles within the empire took advantage of further conflicts with the pope to enhance their position, siding with the church to gain power. They subordinated lesser nobles, expanded restrictions on peasants, and prevented later emperors such as Frederick Barbarossa from unifying the empire.