Starting from Rome’s prestige
The pope was originally the bishop of Rome, one bishop among many. His special standing rested on Rome’s old status as the imperial capital and on the tradition that Saint Peter and Saint Paul had been martyred there. Early popes such as Leo I in the fifth century argued that Peter’s authority passed to his successors in Rome, a claim often called Petrine primacy. Many bishops respected Rome’s opinion without agreeing that it could command them, and the eastern churches, centered on Constantinople, never accepted the full western claim.
After the western empire’s collapse, popes were in practice often local figures, dealing with Italian politics, Lombard pressure and the distant Byzantine Empire. Their influence beyond Italy came partly through missions and partly through alliances with new rulers.
Allies among the Franks
A turning point came in the eighth century, when popes sought protection from the Frankish rulers. Pepin, father of Charlemagne, gave lands in central Italy to the papacy, which became the basis of the later Papal States. In 800, Pope Leo III crowned Charlemagne emperor in Rome. Historians still discuss what each side meant by the act, but it linked the papacy with a new western empire and raised the question of whether pope or emperor held greater authority.
In the following centuries, the papacy was weak at times, caught up in the rivalries of Roman noble families. Rulers and local nobles often controlled who became pope, and the standing of the office suffered.
The reform papacy
From the mid-eleventh century a more assertive group of reformers took hold in Rome. They tried to end simony and clerical marriage and to free the church from lay control. In 1059 new rules gave the cardinals a leading role in electing the pope, reducing the influence of Roman families and emperors.
Gregory VII, pope from 1073 to 1085, pushed the program furthest. A set of statements associated with his papacy, known as the Dictatus Papae, asserted that the pope alone could depose bishops and that he could, in some circumstances, release subjects from loyalty to an unjust ruler. Scholars debate how widely these claims were meant to be applied, but they show how far the reform party was willing to go.
The investiture dispute
The sharpest conflict was over lay investiture: rulers’ practice of choosing bishops and presenting them with the symbols of office. Since bishops held land and offices vital to government, kings and emperors were reluctant to give up this power. Gregory prohibited lay investiture, and the German king Henry IV resisted.
The resulting struggle included excommunication of the king and a famous scene in 1077, when Henry traveled to Canossa in Italy to seek the pope’s forgiveness. The episode is often described as a humiliation of the king, though Henry’s position soon recovered, and the conflict continued for decades. It ended in a compromise, the Concordat of Worms in 1122, which separated the spiritual symbols of a bishop’s office from his lands and left the emperor a say in the process. Neither side won completely, but the papacy had established that it could stand up to the strongest ruler in the west.
Papal authority at its height
The twelfth and thirteenth centuries saw the papacy develop into a legal and administrative power. Popes issued decretal letters answering questions about church law, and canon lawyers organized them into collections. The Curia handled appeals from across Europe.
Innocent III, pope from 1198 to 1216, is often seen as the high point. He intervened in royal successions, in the Holy Roman Empire and elsewhere, and clashed with King John of England over the choice of Archbishop of Canterbury, placing England under an interdict. He also called the Fourth Lateran Council in 1215. Some earlier writers said Innocent claimed to rule the world; most historians now read his language more carefully, as asserting a spiritual authority that gave him the right to judge matters involving sin, including the actions of kings.
Challenges and setbacks
Popes also made enemies. Struggles with the Hohenstaufen emperors dominated much of the thirteenth century, and the papacy used the Crusades and heavy taxation against its political opponents, which drew criticism.
Around 1300, Boniface VIII quarreled with Philip the Fair of France over whether the king could tax the clergy. Boniface issued the bull Unam Sanctam in 1302, which stated that submission to the pope was necessary for salvation. The dispute ended badly for the papacy: Boniface was seized by agents of the French crown in 1303 and died soon after. Shortly afterward, the papal court moved to Avignon, where it stayed for most of the period between 1309 and 1377, which critics said made it too dependent on France.
Matters worsened with the Western Schism, beginning in 1378, in which rival popes each claimed legitimacy. The schism was ended by the Council of Constance in 1417, but it encouraged the idea that a general council might hold authority over a pope.
What the rise really meant
The papacy’s growth was real but uneven. It was strongest where it worked with rulers or provided services, like courts and arbitration, that others wanted. Its claims to be above secular rulers were rarely accepted without argument, and kings developed theories of their own about royal independence. By the end of the Middle Ages the pope was both a spiritual head and a political player, and the difficulty of combining those roles was a lasting source of tension.