After the Church fathers Ireneaus and Tertullian had endorsed Rome as the apostolic city, Clixtus I (217-22) proclaimed the exceptional position of the Roman bishop against the opposition of Tertullian and Origen, and thereby became the creator of the concept of the Papacy. The Church father Cyprian defended the primacy of Peter in terms of the honour due to him. but he was convinced of the legal equality of all bishops. The 4 patriarchates of Jerusalem, Antioch, Alexandria, and Rome were placed on a level of 'spiritual equality' by the Council of Nicea.

After Damasus I (366-84) asserted the teaching authority of the Roman bishop on the basis of the legacy of Peter the evolution from Roman bishop to Pope (Papa) began and Theodosius the Great acknowledged the Bishop of Rome as guardian of the true faith and supreme authority. Siricus (384-99) composed papal letters, borrowing from imperial degrees in form, which testified in the identity of Pope and Peter.

Leo I (440-61), the 'secret Roman Emperor' was the first authentic pope and the founder of the Roman Primacy.

Pope Gregory the Great became the founder of the worldly power of the papacy and gradually the secular ruler of the city of Rome.

The highpoint of papal power came in 1294 when Boniface VIII became pope as the foremost exponent of papal supremacy.

(Quoted from the Penguin Atlas of History)