237. Jovian, the captain of the life-guards, was saluted as Augustus by the generals of Julian. He obtained peace with the Persian king by ceding the five provinces east of the Tigris, and then conducted a difficult retreat to the capital. The principal act of his reign was the re-establishment of Christian worship and of universal tolerance. He died, Feb., A. D. 364, after a reign of eight months. The civil and military officers of the empire met at Nicæa, and chose for their sovereign Valentin´ian, a Christian and a brave soldier, who had distinguished himself by service both on the Tigris and the Rhine. His brother Valens was made his colleague, with the command of the East, extending from the lower Danube to the boundaries of Persia.
238. Valentinian fixed his capital at Milan, which alternated with Rheims and Treves as his headquarters. He signally defeated the Alemanni, and guarded the Rhine by a new series of forts. The coasts of western Europe now began to be overrun by piratical Saxons, while the Picts and Scots swept over all the cultivated fields of southern Britain, from the Wall of Antoninus to the coast of Kent. Theodo´sius, father of the future emperor of that name, led a veteran army to the relief of the Britons, and afterward gained among the Orkneys a great naval victory over the Saxons.
Having defeated the Alemanni on the upper Danube, Theodosius was next sent into Africa to quell a revolt of the Moors and provincials, provoked by the extortions of Count Roma´nus. Firmus, the chief of the Moors, was as wily as Jugurtha, but Theodosius showed all the skill of Metellus or of Scipio. He imprisoned Romanus and restored order to the province; but he was rewarded only by unjust suspicions and a military execution, A. D. 376. Valentinian was already dead (Nov., A. D. 375), and the ministers who surrounded his son disguised the truth to suit their own purposes.
239. Valens, meanwhile reigning in the East, was far inferior to his brother in firmness and beneficence of character. At the beginning of his reign, Proco´pius, a kinsman of Julian, gained possession of Constantinople, and kept it several months as nominal emperor. He was captured at last, and suffered a cruel death in the camp of Valens. The great event of this period was the irruption of a new and terrible race of savages from northern Asia. The Huns were more hideous, cruel, and implacable than even the fiercest of the barbarians hitherto known to the Romans. The Great Wall, which still divides China from Mongolia, had been erected as a barrier against their inroads; but their attention was now turned to the westward, where the Goths, north of the Black Sea, were the first to feel their power.
The great Gothic kingdom of Her´manric extended from the Danube and Euxine to the Baltic, and embraced many kindred tribes, of which the eastern or Ostro-Goths, and the western or Visi-Goths were most important. The former were conquered by the Huns; the latter besought permission from Valens to settle on the waste lands south of the Danube, and become subjects of the empire. Their request was granted, and a million of men, women, and children crossed the river. But the Roman commissioners who were charged with receiving and feeding this starving multitude, seized the opportunity to make their own fortunes, at the expense of their honor and of the safety of the empire.
The Goths had been required to give up their arms, but they purchased of these officers permission to retain them. The food which was served to them was of the vilest quality and most extravagant price. Discontent broke out among the turbulent and armed host. The Gothic warriors marched upon Marcianop´olis, defeated the army which was sent to defend it, and laid waste all Thrace with fire and sword. Instead of pacifying the Goths by a just punishment of the offenders, and by pledges of justice for the future, Valens sent for aid to his nephew Gratian, and advanced with his army to fight with the barbarians. In a battle near Hadrianople he was slain, and two-thirds of his army perished, A. D. 378.
240. Gratian, the son of Valentinian, had been three years emperor of the West, and now became sole sovereign of the dominions of Augustus. He chose, however, for a colleague, the general Theodosius, to whom he committed the empire of Valens, with the addition of the province of Illyricum. The youth of Gratian was adorned by a fair promise of all the virtues; but as soon as his excellent instructors left him, he proved himself weak and wholly unfit for command. Bad men gained and abused his confidence.
Maximus, in Britain, revolted, and passed over into Gaul with an army. Instead of fighting, Gratian fled from Paris; his armies deserted to the enemy, and the fugitive emperor was overtaken and slain at Lyons, A. D. 383. He had already, on his accession, shared the imperial dignity with his brother, Valentinian II., then only five years of age. Maximus, being in actual possession of the countries west of the Alps, was acknowledged by Theodosius, on condition of the young Valentinian being left in secure possession of Italy and Africa. The sovereign of Gaul, Spain, and Britain soon became strong enough to break his word. He invaded Italy, and the young emperor, with Justi´na his mother, fled to the court of Theodosius for protection. The emperor of the East marched to attack Maximus, whom he defeated and caused to be executed as a traitor, and established Valentinian II. in the sovereignty of the whole Western empire.
241. The young sovereign of the West proved as weak as his brother. He fell under the control of an officer of his own, a Frank named Arbogas´tes; and when he attempted to shake off the yoke, the too powerful servant murdered his master and set up an emperor of his own choosing. Euge´nius reigned two years (A. D. 392-394), as the tool of Arbogastes; but Theodosius at length defeated his army near Aquileia, and put him to death.