St. Athanasius (b. around 297, died 373) was Bishop of Alexandria known as the "Father of Orthodoxy." He was the great champion of the faith against the widespread heresy of Arianism. Athanasius led a tumultuous but dedicated life of service promoting the Catholic belief of the Incarnation. His ascetical writings contributed greatly to the establishment of monastic life throughout the Western Christian world. This would earn him the title Doctor of the Church.
Born of a Christian family in Alexandria, Egypt, and given a classical education. He grew up during the persecution of Christians by Roman Emperor Maximianus and the cancelling of persecution edicts against the Christians by Roman Emperor Constantine. Legend says that Bishop Alexander of Alexandria was waiting for his guests to arrive, he stood by a window, watching a group of boys at play on the seashore below the house. He had not observed them long before he discovered that they were imitating the elaborate ritual of Christian baptism. He therefore sent for the children and had them brought into his presence. In the investigation that followed it was discovered that one of the boys, Athanasius, had acted the part of the bishop, and in that character had actually baptized several of his companions in the course of their play.  Alexander decided that Athanasius and his playfellows should go into training in order to fit themselves for a clerical career. Under the tutelage of Alexander, he made great progress in learning and virtue. He became deacon then priest and from Bishop Alexander's recommendation, Athanasius would replace him as Bishop of Alexandria in 326.
Council of Nicaea
Athanasius assisted Bishop Alexander at the Council of Nicaea. The Council was requested by Constantine due to the schisms over the distribution of authority in the Church and over doctrinal questions. Arius, a priest of the Alexandrian Church, had denied the Divinity of Christ. Thus began the heresy of Arianism. With only two dissenting voices the Bishops condemned them as heresy, and deposed Arius, together with eleven priests.  Arius retired to Caesarea, where he continued to propagate his ideas, enlisting the support of Bishop Eusebius of Nicomedia and other Syrian prelates. After the death of Bishop Alexander, Athanasius vigorously defended the Councils edicts. Yet in spite of his best efforts, there was strong opposition. At the same time, Arius was plotting his comeback and gaining support. In 330, the Arian bishop of Nicomedia had persuaded the aging Constantine to write to Athanasius, bidding him readmit Arius into communion. Athanasius held to his conviction that the Church could have no communion with heretics who attacked the divinity of Christ. Then the Arian Bishop wrote the Egyptian Meletians urging them to impeach Athanasius for personal misconduct. They brought charges and other petty accusations. At his trial before the emperor, Athanasius cleared himself and returned in triumph to Alexandria, bearing with him a letter of approval from Constantinople. Then, for some unexplained reason, Constantine suddenly changed his mind and banished Athanasius to Treves. During this first exile, Athanasius kept in touch with his flock by letter.
Death of Constantine
Upon the Emperors death, Constantine II became ruler and allowed Athanasius to return to his See. Two years later, Constantine II was to be killed in battle in Aquileia and replaced by Emperor Constantius who sided with the Arians. Once again, new scandals were invented and Athanasius was now accused of raising sedition, promoting bloodshed, and keeping for himself corn intended for the poor. A Church council which met at Antioch again deposed him, and ratified an Arian bishop for Alexandria, Cappadocian priest named Gregory. Athanasius betook himself to Rome to await the hearing of his case by the Pope. A synod was summoned and the result was a complete vindication of Athanasius, a verdict afterwards endorsed by the Council of Sardica. After the death of Gregory, Emperor Constantius restored Athanasius to his see. After an absence then of eight years, Athanasius was welcomed back to Alexandria in 346. At Arles in 353, Emperor Constantius obtained the condemnation of Athanasius from a council of Gallic bishops. Opposition from the Italian bishops, Constantius with his hand on his sword he gave them their choice between condemnation of Athanasius and exile.  The few stubborn bishops were exiled, including the new Pope Liberius. Then one night, as he was celebrating a vigil in the church of St. Thomas, soldiers broke in. Athanasius was instantly surrounded by his people, who swept him out into the safety of darkness; but for six years thereafter he had to live in hiding. The death of Constantius in 361 was followed by another shift in the situation. The new pagan Emperor Julian, revoked the sentences of banishment enacted by his predecessors, and Athanasius returned once again to his own city. But it was only for a few months. Julian had also considered it necessary to banish Athanasius from Alexandria as "a disturber of the peace and an enemy of the gods." The new emperor, Jovian, a soldier of Catholic sympathies, revoked the sentence of banishment and invited Athanasius to Antioch, to expound the doctrine of the Trinity. Jovian's reign lasted only a year. The new Emperor Valens, succumbed to Arian pressure in Constantinople and in May 365, issued an order banishing again all orthodox bishops who had been exiled by Constantius and restored by his successors. Four months later, Emperor Valens revoked his edict, who was determined to accept no other man as Bishop. Joyfully they escorted him back. Athanasius had spent seventeen years in exile, but his last years were peaceful. After a life of virtue and suffering, this intrepid champion of the Catholic Faith, the greatest man of his time, he died in Alexandria on May 2, 373.
The statement of Christian doctrine known as the Athanasian Creed was probably composed during his life, but not actually by him.