The history of the Catholic Church is traced by the Catholic Church back to apostolic times and thus covers a period of nearly 2,000 years, making it one of the world's oldest institutions. The history of the Catholic Church is an integral part of the history of Christianity and of Western civilization.
The Catholic Church was founded by Jesus Christ, its spiritual head. Catholic doctrine asserts that it is the continuation of the Church that was founded at the Confession of Peter. It interprets the Confession of Peter as Christ's designation of Apostle Peter and his successors in Rome to be the temporal head of his Church. Thus, it asserts that the Bishop of Rome has the sole legitimate claim to Petrine authority and the primacy due to the Roman Pontiff. The Catholic Church claims legitimacy of its bishops and priests via the doctrine of apostolic succession and authority of the Pope via the unbroken line of popes, successors to Simon Peter.
The authority of the Apostle Peter and his successors is thus viewed as a continuous history from Jesus Christ. The institution of the papacy as it exists today developed through the centuries. Church tradition records that Peter became the first leader of Christians in the Imperial capital of Rome. The Apostles and many Christians traveled to northern Africa, Asia Minor, Arabia, Greece, and Rome to found the first Christian communities. Christianity spread quickly through the Roman Empire, and by the second century there were many established bishoprics within the Empire including Northern Africa, France, Italy, Syria, and Asia Minor, and twenty bishoprics outside the empire, mainly in Armenia. Irenaeus (d. 202) defended the apostolic tradition.
In 313, the struggles of the Early Church were lessened by the legalisation of Christianity by the Emperor Constantine I. In 380, Christianity became the state religion of the Roman Empire by the decree of the Emperor, which would persist until the fall of the Western Empire, and later, with the Eastern Roman Empire, until the Fall of Constantinople. During this time (the period of the Seven Ecumenical Councils) there were considered five primary sees according to Eusebius: Rome, Constantinople, Antioch, Jerusalem and Alexandria, see also Pentarchy.
After the destruction of the western Roman Empire, the church in the West was a major factor in the preservation of classical civilization, establishing monasteries, and sending missionaries to convert the peoples of northern Europe, as far as Ireland in the north. In the East, the Byzantine Empire preserved Orthodoxy, until the massive invasions of Islam in the mid-seventh century. The invasions of Islam devastated three of the five patriarchal sees, capturing Jerusalem first, then Alexandria, and then finally in the mid-eighth century, Antioch.
The whole period of the next five centuries was dominated by the struggle between Christianity and Islam throughout the Mediterranean Basin. The battles of Poitiers, and Toulouse preserved the Catholic west, even though Rome itself was ravaged in 850, and Constantinople besieged.
In the 11th century, already strained relations between the primarily Greek church in the East, and the Latin church in the West, developed into the East-West Schism, partially due to conflicts over Papal Authority. The fourth crusade, and the sacking of Constantinople by renegade crusaders proved the final breach.
In the 16th century, in response to the Protestant Reformation, the Church engaged in a process of substantial reform and renewal, known as the Counter-Reformation. In subsequent centuries, Catholicism spread widely across the world despite experiencing a reduction in its hold on European populations due to the growth of religious scepticism during and after the Enlightenment. The Second Vatican Council in the 1960s introduced the most significant changes to Catholic practices since the Council of Trent three centuries before.