Magnus Maximus in the context of "Gratian"

Roman rule in Britain ended as Roman military forces withdrew to defend or seize the Western Roman Empire's continental core, leaving behind an autonomous post-Roman Britain. In 383, the usurper Magnus Maximus withdrew troops from northern and western Britain, probably leaving local warlords in charge. In 407, the usurper Constantine III took the remaining mobile Roman soldiers to Gaul in response to the crossing of the Rhine, and external attacks surged. The Romano-British deposed Roman officials around 410, and government largely reverted to city level. That year Emperor Honorius refused an appeal from Britain for military assistance. The following decades saw the collapse of urban life and the Anglo-Saxon settlement of Britain.

The pontifex maximus (Latin for 'supreme pontiff') was the chief high priest of the College of Pontiffs (Collegium Pontificum) in ancient Rome. This was the most important position in the ancient Roman religion, open only to patricians until 254 BC, when a plebeian first held this position. Although in fact the most powerful office in the Roman priesthood, the pontifex maximus was officially ranked fifth in the ranking of the highest Roman priests (Ordo Sacerdotum), behind the Rex Sacrorum and the flamines maiores (Flamen Dialis, Flamen Martialis, Flamen Quirinalis).

A distinctly religious office under the early Roman Republic, it gradually became politicized until, beginning with Augustus, it was subsumed into the position of emperor in the Roman imperial period. Subsequent emperors were styled pontifex maximus well into Late Antiquity, including Gratian (r. 367–383), but during Gratian's reign the phrase was replaced in imperial titulature with the Latin phrase: pontifex inclytus ("honourable pontiff"), an example followed by Gratian's junior co-emperor Theodosius the Great and which was used by emperors thereafter including the co-augusti Valentinian III (r. 425–455), Marcian (r. 450–457) and the augustus Anastasius Dicorus (r. 491–518). The first to adopt the inclytus alternative to maximus may have been the rebel augustus Magnus Maximus (r. 383–388).

Magnus, meaning "Great" in Latin, was used as cognomen of Gnaeus Pompeius Magnus in the first century BC. The best-known use of the name during the Roman Empire is for the fourth-century Western Roman Emperor Magnus Maximus. The name gained wider popularity in the Middle Ages among various European peoples and their royal houses, being introduced to them upon being converted to the Latin-speaking Catholic Christianity. This was especially the case with Scandinavian royalty and nobility.

As a Scandinavian forename, it was extracted from the Frankish ruler Charlemagne's Latin name "Carolus Magnus" and re-analyzed as Old Norse magn-hús = "power house".

Valentinian II (Latin: Valentinianus; 371 – 15 May 392) was a Roman emperor in the western part of the Roman Empire between AD 375 and 392. He was at first junior co-ruler of his half-brother, then was sidelined by a usurper, and finally became sole ruler after 388, albeit with limited de facto powers. He was the youngest emperor (co-ruler) in the Western Roman Empire (aged 4).

A son of emperor Valentinian I and empress Justina, he was raised to the imperial office at the age of four by military commanders upon his father's death. Until 383, Valentinian II remained a junior partner to his older half-brother Gratian in ruling the Western empire, while the East was governed by his uncle Valens until 378 and Theodosius I from 379. When the usurper emperor Magnus Maximus killed Gratian in 383, the court of Valentinian II in Milan became the locus of confrontations between adherents to Nicene and Arian Christianity. In 387, Maximus invaded Italy, spurring Valentinian II and his family to escape to Thessalonica where they successfully sought Theodosius's aid. Theodosius defeated Maximus in battle and re-installed Valentinian II.

Quintus Aurelius Symmachus signo Eusebius (/ˈsɪməkəs/, Classical Latin: [ˈsʏmmakʰʊs]; c. 345 – 402) was a Roman statesman, orator, and intellectual. He held the offices of governor of proconsular Africa in 373, urban prefect of Rome in 384 and 385, and consul in 391. Symmachus sought to preserve the traditional religions of Rome at a time when the aristocracy was converting to Christianity, and led an unsuccessful delegation of protest against Emperor Gratian's order to remove the Altar of Victory from the curia, the principal meeting place of the Roman Senate in the Forum Romanum. Two years later he made a famous appeal to Gratian's successor, Valentinian II, in a dispatch that was rebutted by Ambrose, the bishop of Milan. Symmachus's career was temporarily derailed when he supported the short-lived usurper Magnus Maximus, but he was rehabilitated and three years later appointed consul. After the death of Theodosius I, he became an ally of Stilicho, the guardian of Emperor Honorius. In collaboration with Stilicho he was able to restore some of the legislative powers of the Senate. Much of his writing has survived: nine books of letters; a collection of Relationes or official dispatches; and fragments of various orations.

Ambrose of Milan (Latin: Aurelius Ambrosius; c. 339 – 4 April 397), canonized as Saint Ambrose, was a theologian and statesman who served as Bishop of Milan from 374 to 397. He expressed himself prominently as a public figure, fiercely promoting Nicene Christianity against Arianism and paganism. He left a substantial collection of writings, of which the best known include the ethical commentary De officiis ministrorum (377–391), and the exegetical Exameron [it] (386–390). His preaching, his actions and his literary works, in addition to his innovative musical hymnography, made him one of the most influential ecclesiastical figures of the 4th century.

Ambrose was serving as the Roman governor of Aemilia-Liguria in Milan when he was unexpectedly made Bishop of Milan in 374 by popular acclamation. As bishop, he took a firm position against Arianism and attempted to mediate the conflict between the emperors Theodosius I and Magnus Maximus. Tradition credits Ambrose with developing an antiphonal chant, known as Ambrosian chant, and for composing the "Te Deum" hymn, though modern scholars now reject both of these attributions. Ambrose's authorship on at least four hymns, including the well-known "Veni redemptor gentium", is secure; they form the core of the Ambrosian hymns, which includes others that are sometimes attributed to him. He also had a notable influence on Augustine of Hippo (354–430), whom he helped convert to Christianity.