Illyricum, Praetorian prefecture of

Emperor Theodosius, residing chiefly in Thessalonica, seeks first to rebuild the imperial army, the discipline of which is considerably impaired, and to consolidate Rome's position on the Balkan peninsula.

Military unpreparedness cannot be overcome by conscription alone, which applies only to certain classes.

Theodosius therefore directs that the army accept large numbers of Germans, who had been barred from military service.

Foreigners have by 379, however, already intermingled extensively with the rest of the army, both among the troops and in all ranks of the officer corps, so Theodosius does no more than many of his predecessors to encourage this process.

Both Romans and Germans are among the leading generals in Theodosius' provinces, in contrast to the West.

Theodosius' situation is complicated by the sharp antagonism that arises around 379 between disciples of the Nicene Creed (according to which Jesus Christ is of the same substance as God the Father) and several other Christian groups in his part of the empire.

The Goths, who by 380 can no longer be driven from the empire, divide into Therving and Greuthung armies, in part because of the difficulty of keeping such a large number supplied.

The Greuthungs move north into Pannonia, where Gratian in 380 agrees with a cluster of three tribal armies to settle them on vacant lands as a unit under their own chiefs.

The Thervings under Fritigern move south and east to Macedonia, where they take "protection money" from towns and cities rather than sacking them outright.

The Christian Church has become synonymous with the Roman Empire by about 380 , but Theodosius finds his realm divided between rival orthodox and Arian Christian groups.

Propelled by political as well as religious motives, he energetically undertakes to bring about unity of faith within the empire.

Soon dominating his weak colleague, Theodosius enters the battle on the side of orthodoxy, becoming the first emperor who does not assume the title of pontifex maximus (supreme guardian of the old Roman cults).

His position has been improved by the fact that during 379 the followers of the Nicene Creed had gained ground, whereupon Theodosius, without consulting the ecclesiastical authorities, issues an edict on February 28, 380, prescribing a creed that is to be binding on all subjects.

Only persons who believe in the consubstantiality of God the Father, Son, and Holy Spirit are henceforth to be considered Catholic Christians, a designation that here appears for the first time in a document.

Although Theodosius’ belief in the Nicene Creed is apparently genuine, he submits to baptism in the fall of 380 only after a serious illness.

The Hasdingi, the larger of the two branches of Vandals, had already been Christianized during the first half of the fourth century.

During the reign of Emperor Valens (364–78) the Vandals had accepted, much like the Goths earlier, Arianism, a belief that was in opposition to that of Nicene orthodoxy of the Roman Empire.

Yet there are also some scattered orthodox Vandals, among whom is the famous magister militum Stilicho, the chief minister of the Emperor Honorius.

Theodosius, having ordered one army division from Egypt to Africa and having sent young Valentinian II with a fleet to Italy, sets out in the spring of 388 with the main body of troops to move against the army of the usurper Maximus, now invading Pannonia in the Balkans.

His son Arcadius, an augustus since 383, represents him in the East.

Maximus, upon the defeat of his troops near Siscia and at Poetovio, in Illyricum (in the Balkans) in July, flees to Italy, pursued by Theodosius as his navy gains command of the Adriatic Sea.

Theodosius has campaigned against Maximus in Illyrium, where he has bested the western emperor in two encounters, one involving a sudden and courageous river crossing.

Upon the defeat in July of Maximus's troops near Siscia and at Poetovio, in Illyricum (in the Balkans), while Maximus is surrounded in Aquileia by Theodosius, Maximus is betrayed by his soldiers and delivered at the end of August to Theodosius, who brands him as a usurper, orders his execution, and restores Valentinian to his throne in 388.

The followers of Maximus are generally treated with leniency.

The Dream of Macsen, one of the eleven tales in the medieval Welsh Mabinogion, tells a legendary version of Maximus's rise to power.

Theodosius, to safeguard Greece after a series of raids by the Goths, had stationed a large number of troops under General Butheric in Thessalonika, a city that had never been a garrison town.

The Thessalonians resent having to maintain the army, and tensions mount as quarrels between the soldiers and the citizens increase in number.

The trouble comes to a head in the summer of 390 when a popular charioteer makes a sexual advance to one of Butheric's attendants.

The general, taking the incident as a personal insult, has the charioteer thrown into prison.

When a mob gathers to protest the confinement of one of their favorite athletes, the demonstration degenerates into a riot in which Butheric is killed.

In retaliation for the murder of his general, Theodosius looses his troops on the city, making no attempt to sort the guilty from the innocent.

In the space of only three hours, seven thousand men, women, and children are massacred.

Constantine I had initiated a general Christian policy  to slowly end both public and private religious freedom and establish universal Christian worship in accordance with the doctrines set forth in the Nicene Creed.

Theodosius, feeling that the Olympic Games have pagan connotations, in 393 suspends the thousand-year-old festival; he will officially ban them the following year.