Damasus, who had served as an assistant deacon to Liberius since his installation in 352, wins the support of the Roman people to become pope on October 1, 366, following the death of Antipope Felix II.

Of Spanish descent, Damasus, uneasy at the growing power of Constantinople, attempts to strengthen his position by insisting on the apostolic foundations of the Roman see.

An adherent of orthodoxy, he works to suppress Arianism and other church heresies.

Two synods held in 368 and 369 had condemned the unorthodox teachings of Bishop Macedonius of Constantinople and of Bishop Apollinaris (the Younger) of Laodicea.

Among Damasus' literary remains are twenty-four anathemas against various fourth-century heresies.

With a view to the elimination of Arianism in the East, he enters into lengthy negotiations with Basil, who, as the new bishop of Caesarea, is head of the church throughout most of Anatolia (Turkey).

Their dealings are not a success: though united against Arianism, they fail to agree on policies.

Valentinian does, however, legislate in favor of Rome‘s university, the nursery of imperial officials, by his law of 370.

In this year, laws of Valentinian and Valens ban marriages between Romans and barbarians under penalty of death; an edict issued by both emperors bans the importation of wine and olive oil from areas controlled by the barbarians.

Religious peace reigns in the West, where tolerance is proclaimed.

Rome, after some difficulty, has found a great pope in Damasus.

When the Arian bishop of Milan, Auxentius, dies in 374, and the Arians challenge the succession.

Ambrose, the consular prefect or "Governor" of Liguria and Emilia, with headquarters at Milan, goes to the church where the election is to take place, to prevent an uproar, which is probable in this crisis.

His address is interrupted by a call "Ambrose, bishop!", which is taken up by the whole assembly.

A bachelor born into a Roman Christian family between about 337 and 340 and raised in Trier, Ambrose is known to be orthodox in belief, but also acceptable to Arians due to the charity shown in theological matters in this regard.

At first he energetically refuses the office, for which he is in no way prepared: although his strong rule, modesty, and rhetorical skill have made him a tremendously popular governor, Ambrose has neither been baptized nor formally trained in theology.

Upon his appointment, Ambrose flees to a colleague's home to seek hiding.

Upon receiving a letter from the Emperor praising the appropriateness of Rome appointing individuals evidently worthy of holy positions, Ambrose's host surrenders his guest.

Within a week, Ambrose is baptized, ordained and duly installed as bishop of Milan.

As bishop, he immediately adopts an ascetic lifestyle, apportions his money to the poor, donating all of his land, making only provision for his sister Marcellina (who will later become a nun), and commits the care of his family to his brother.

Ambrose also writes a treatise by the name of "The Goodness Of Death".

According to legend, Ambrose immediately and forcefully stops Arianism in Milan.

General Theodosius the Younger, who has remained in retirement in Spain following the execution of his father, had married a fellow Spaniard, Aelia Flacilla, at the end of 376.

Theodosius' first son, the future emperor Arcadius, had been born in 377, and his daughter Pulcheria in January 378.

Immediately after the catastrophic defeat and death of Valens at Adrianople, Gratian unexpectedly summons to his court Theodosius to control the incursions.

When Theodosius once again proves his military ability by a victory over the Sarmatians, Gratian, before the army, proclaims him co-emperor on January 19, 379.

The extremely pious Gratian, having come under the influence of Bishop Damasus or Rome and of Bishop Ambrose of Milan, has chosen Theodosius not only for his military ability but also for his orthodoxy.

His dominion is to be the eastern part of the empire, including the provinces of Dacia (present-day Romania) and Macedonia, taken from Gratian's stepbrother, the augustus Valentinian II, which have been especially infiltrated by barbarians in the preceding few years.

Gratian has spent most of his reign in Gaul repelling the tribes that are invading Gaul from across the Rhine.

Influenced from the outset by Ausonius, whom he had made consul in 379, he has sought to make his rule mild and popular.

For some years, he has governed the empire with energy and success but has gradually sank into indolence, occupying himself chiefly with the pleasures of the chase, and become a tool in the hands of the Frankish general Merobaudes and bishop Ambrose of Milan.

Now greatly influenced by Ambrose, he codifies the separation between East and West.

The Westerners, satisfied with the triumph of orthodoxy, bow to this policy.

Ambrose and Damasus, operating now with official state support, deal harshly with the Arians.

Paganism also is hounded: following Theodosius' lead, Gratian refuses the chief priesthood, removes the altar of Victory from the hall of the Roman Senate, and deprives the pagan priests and the Vestal Virgins of their subsidies and privileges.

The pagan senators are outraged, but their protests are futile because Gratian is watched over by Ambrose.

Gratian also publishes an edict that all their subjects should profess the faith of the bishops of Rome and Alexandria (i.e., the Nicene faith).

The move is mainly aimed at the various beliefs that had arisen out of Arianism, but smaller dissident sects, such as the Macedonians, are also prohibited.

Named after Bishop Macedonius of Constantinople, the Macedonian sect, regarded as heretical by the mainstream church, professes a belief similar to that of Arianism, denying the divinity of the Holy Spirit, and regarding the essence of Jesus Christ as being the same in kind as that of God the Father.

The sect's members are also known as pneumatomachians, the “spirit fighters.” The nature of the connection between the Macedonians and Bishop Macedonius is unclear; most scholars today believe that Macedonius had died (around 360) before the sect emerged.

Damasus, perhaps wary of the growing strength of Constantinople, which is already claiming to be the New Rome, calls a synod that officially pronounces Rome's primacy.

Jerome, having returned to Rome around this time, stays on to become Damasus' secretary, close adviser, and friend.

Damasus does not receive Priscillian and his key followers but they manage to gain absolution from civil authorities, who ultimately enable the Priscillians to force Ithacius from Spain.

Jerome, invited to Rome originally to the synod of 382 held for the purpose of ending the schism of Antioch, has made himself indispensable to Pope Damasus, and taken a prominent place in his councils.

Among other duties he has undertaken the revision of the text of the Latin Bible on the basis of the Greek New Testament and the Hebrew Old Testament, in order to put an end to the marked divergences in the current western texts.

Prior to Jerome's translation, all Old Testament translations had been based on the Septuagint.

Jerome has chosen, against the pleadings of other Christians including Augustine himself, to use the Hebrew Old Testament instead of the Septuagint.

The commission to translate the Bible into Latin will determine the course of Jerome’s scholarly activity for many years, and will be his most important achievement.

His translation of the Bible from Greek to Latin is called the Vulgate (vulgar) because it is in the common, or vulgar, tongue of the people.

He has undoubtedly exercised an important influence during these three years in Rome, to which, outside of his unusual learning, his zeal for ascetic strictness and the realization of the monastic ideal have contributed not a little.

A circle of well-born and well-educated women, including some from the noblest patrician families, such as the widows Marcella and Paula, with their daughters Blaesilla and Eustochium, surround Jerome.

The resulting inclination of these women for the monastic life, and his unsparing criticism of the life of the secular clergy, brought a growing hostility against him among the clergy and their supporters.

Soon after the death of his patron Damasus on December 10, 384, and having lost his necessary protection, Jerome is forced to leave his position at Rome following an inquisition of the Roman clergy into allegations that he had improper relations with the widow Paula.