The problem, in fact, was probably not so much lack of the will to survive on the part of the government as the continued pressures of these invaders. The ongoing wars with the Sasanians were manageable in the sense that Sasanian Persia was a centralized state that could be negotiated with, although there were other factors involved, including the ambitions of leaders on both sides, which prevented peace. However, there was no easy way to control the northern borders of the empire. Valentinian had managed to preserve the frontiers but had died suddenly in 375, from an apoplectic fit brought on when negotiating with some intransigent Germans. His successor, his son Gratian whom he had made an Augustus when only 8, was now 16. (The troops also declared Valentinian’s 4-year-old son, another Valentinian, as
Augustus. Not for the first time there was a clash here between the needs of the empire for strong rulers and the determination of those emperors in power to maintain a dynasty.) Gratian and his co-emperor, his uncle Valens, now faced a massive incursion of Goths, as a hitherto unknown people, the Huns, appeared from the east. The Huns were nomadic peoples who, for some reason, possibly major economic changes in the steppes of central Asia, had been forced into migration. Ammianus is at his best as he describes this ‘wild race moving without encumbrances and consumed by a savage passion to pillage the property of others’. The Goths were pushed helplessly towards the boundaries of the empire and soon a mass of refugees was struggling to cross the Danube.
Faced with this incursion Valens saw it as an opportunity to recruit men for the overstretched Roman armies. However, far from organizing the recruitment in an orderly way, local soldiers treated the new arrivals with contempt. There were reports of Roman officers offering the Goths’ leaders dogs for food in return for the surrender of their men as slaves. The Goths were outraged, broke free from Roman control, and were soon rampaging through Thrace. Valens had to march from Constantinople to subdue them, but at the Battle of Adrianople, 9 August 378, the Romans were caught by an overpowering mass of armed Goths. Hemmed in on all sides they lost the ability to manoeuvre, traditionally an effective part of Roman strategy. Two-thirds of the Roman army, possibly 10,000 of its best troops, died in the humiliating defeat. Valens fell among them.
This humiliation is often seen as a turning point in the history of the empire, the moment when the Romans finally lost the initiative against the invaders. This may be an exaggeration. The armies had been under pressure for decades and the defeat at Adrianople may have been no more than one further step in a steady process of the weakening of the empire. However, a significant development in the relationships between Romans and barbarians now took place. Gratian appointed an efficient Spanish general, Theodosius, to succeed Valens and, in 382, Theodosius signed a treaty with the Goths under which they were allowed to settle in the empire, in Thrace, in return for providing troops for the Roman armies. Their position was to be one of privilege. They were to be exempt from taxation and able to serve under their own leaders. There were precedents for such compromises but this was the first time that an area within the borders of the empire had been passed out of effective Roman control. Within a few years the Goths were to be once again on the move, causing havoc as they searched for new land (see below, p. 630 ff.).
Gratian was killed in 383 when fighting a western usurper, Maximus. His younger brother Valentinian emerged as his successor. Theodosius tolerated Maximus until the latter invaded Italy, forcing Valentinian to flee. Theodosius rushed westwards and defeated and killed him at Aquileia in 388. Valentinian was pushed aside and, in effect, Theodosius was now sole emperor until his death in 395. It was then that the empire was divided between his two sons, Arcadius in the east and Honorius in the west. It was never to be reunited.