Early years as emperor
In 379 and 380 Theodosius resided chiefly in Thessalonica. He sought first to rebuild the army, the discipline of which was considerably impaired, and to consolidate Rome’s position on the Balkan Peninsula. Military unpreparedness could not be overcome by conscription alone, which applied only to certain classes. Theodosius therefore directed that large numbers of Teutons, who had been barred from military service, be accepted by the army. By 379, however, when foreigners had already intermingled extensively with the rest of the army, both among the troops and in all ranks of the officer corps, Theodosius did no more than many of his predecessors to encourage this process. In contrast to the West, in Theodosius’s provinces both Romans and Teutons were among the leading generals.
Recognizing that the barbarians, who had invaded the provinces as early as 375, could no longer be expelled by force and that he could count on Gratian for only limited assistance, Theodosius sought new possibilities for coexistence. This resulted in the friendly reception of the Visigoth Athanaric in 381 and the conclusion of a treaty of alliance, or foedus, with the main body of the Visigoths in the fall of 382. The Goths, who pledged themselves to lending military assistance, were assigned territory for settlement between the lower Danube and the Balkan mountains. Under this novel arrangement, an entire people was settled on imperial soil while retaining its autonomy. Theodosius may have hoped that the Goths would become integrated, as had a group of Goths who had settled near Nicopolis in Moesia circa 350; their leader, Bishop Ulfilas, undertook missionary work among the parties to the foedus of 382.
Some historians have regarded Theodosius as biased in favour of the Goths. He has even been accused of having contributed decisively, through the treaty of 382, to the downfall of Rome. Yet, it should be noted that the policy of that treaty, which was undertaken in the justified expectation of raising Roman military strength and recultivating tracts of wasteland, by no means became customary. Instead, the emperor took strict measures against further invasions by Teutonic bands and did not permit any doubts to arise as to Roman claims of superiority over the barbarians.
Theodosius’s situation was complicated by the sharp antagonism that arose about 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. Theodosius himself, the first emperor who did not assume the title of pontifex maximus (supreme guardian of the old Roman cults), believed in the Nicene Creed, despite his baptism only after a serious illness in the fall of 380.
Out of political as well as religious motives, he energetically undertook to bring about unity of faith within the empire. His position was improved by the fact that during 379 the followers of the Nicene Creed gained ground, whereupon Theodosius on February 28, 380, without consulting the ecclesiastical authorities, issued an edict prescribing a creed that was to be binding on all subjects. Only persons who believed in the consubstantiality of God the Father, Son, and Holy Spirit were henceforth to be considered Catholic Christians, a designation that here appears for the first time in a document.
There is no doubt that the principle of religious intolerance was proclaimed in this edict. When assessing the edict, however—which should not be viewed simply as an isolated measure—it must be remembered that to the Christians Theodosius was emperor by the grace of God. While thus committed to defend the true faith, he by no means carried out his stated intention by force. The creed, prescribed in 380, was again defined at the beginning of 381 and ecclesiastically sanctioned, as it were, by a church council summoned to Constantinople by Theodosius in the summer of 381. That gathering is considered the second ecumenical council.
The Symbolum Nicaeno-Constantinopolitanum (i.e., the Niceno-Constantinopolitan Creed [or Symbol]), which is still used by most Christians, along with the ranking by the council fathers of the bishop of Constantinople directly after the bishop of Rome, can thus be traced back to Theodosius. Henceforth, the emperor’s authority in matters of faith was to be recognized by the bishops of the East. There is no ground, however, for speaking of a rigidly organized imperial church controlled by the emperor.
The period when Theodosius stayed mainly in Constantinople, dating from the end of 380 to 387, is that to which most of his measures to improve the capital may be attributed. The plan for the Forum Tauri, the largest public square known in antiquity, designed after the model of Trajan’s Forum in Rome, is outstanding. It is unclear, however, to what extent the emperor encouraged the flowering of art and literature in his time.