In the years 371 to 377 Valens was in Asia Minor, most of the time at the Syrian Antioch. The late war with Persia under the emperors Julian and Jovian had not been satisfactorily concluded: the question as to the possession or the protectorate of Armenia was still in suspense. Valens, though anxious to avoid an Eastern war, because of danger nearer home from the restlessness of the Goths, was compelled to take the field against Sapor, who had invaded and occupied Armenia. It seems that Valens crossed the Euphrates in 373, and in Mesopotamia his troops drove back the king of Persia to the farther bank of the Tigris. But the Roman success was by no means decisive, and no definite understanding as to boundaries was come to with Persia. Valens returned to Antioch, where in the winter of 373 a young man of high rank, Theodorus by name, was made to believe by a pack of fortune-tellers and magicians that the emperor’s successor would be a man whose name began with “Theod.” Theodorus was put to death, with many others whose name began with the same fatal letters; and this led to a vindictive persecution throughout the province of Asia of all who professed or practised magic and necromancy. The age was a very superstitious and inquisitive one, and Valens certainly shared its weakness. Between 374 and 377 we read of grievous complaints of injustice and extortion perpetrated under legal forms, the result probably of the recent panic, and pointing to an increasing weakness and timidity at headquarters. Although preparations were made for following up the war with Persia and securing the frontier, a truce was patched up, rather to the disadvantage of the empire, Armenia and the adjacent country being half conquered and annexed by Sapor. The armies of Rome, in fact, were wanted in another quarter. The Huns, of whom we now hear for the first time, were beginning in 376 to press the Goths from the north, and the latter asked leave of the emperor to cross the Danube into Roman territory. This they were allowed to do, on the condition that they came unarmed, and their children were transported to Asia as hostages. The conditions, however, were not strictly enforced, and the whole affair was treacherously mismanaged by the imperial generals, who for their own profit forced the new settlers to buy food at famine prices. Accordingly the enraged Goths, under their chief Frithigern, streamed across the Balkans into Thrace and the country round Adrianople, plundering, burning, and slaughtering as they went. They were driven back for a time, but returned in the spring of 378 in greater force, with Huns and Alans to fight with them against the empire; and again, after one or two repulses, they penetrated to the neighbourhood of Adrianople. Valens, who had now returned to Constantinople, left the capital in May 378 with a strong and well-officered army. Without awaiting the arrival of his nephew Gratian, emperor of the West, who had just won a great victory over one of the barbarous tribes of Germany in Alsace, Valens attacked the enemy at once, although his troops had to go into action heated and fatigued by a long march on a sultry August day. The battle was decided mainly by the cavalry of the Alans and Sarmatians, the Roman infantry being outnumbered, outmanoeuvred, and finally so hemmed in that the men could scarcely draw their swords. The slaughter went on for hours, till the imperial army was destroyed. Valens either perished on the field or, as some said, in a cottage fired by the enemy. From the battle of Adrianople the Goths permanently established themselves south of the Danube.

Ammianus Marcellinus, a contemporary writer, is our chief authority for the reigns of Valens and Valentinian. See also Gibbon’s sketch of the period in the 26th and 27th chapters of his Decline and Fall and Hodgkin’s Italy and her Invaders.