The Ecclesiastical History of Socrates Scholasticus

Not long after the barbarians had entered into a friendly alliance with one another, they were again vanquished by other barbarians, their neighbors, called the Huns; and being driven out of their own country, they fled into the territory of the Romans, offering to be subject to the emperor, and to execute whatever he should command them. When Valens was made acquainted with this, not having the least presentiment of the consequences, he ordered that the suppliants should be received with kindness; in this one instance alone showing himself compassionate. He therefore assigned them certain parts of Thrace for their habitation, deeming himself peculiarly fortunate in this matter: for he calculated that in future he should possess a ready and well-equipped army against all assailants; and hoped that the barbarians would be a more formidable guard to the frontiers of the empire even than the Romans themselves. For this reason he in the future neglected to recruit his army by Roman levies; and despising those veterans who had bravely straggled and subdued his enemies in former wars, he put a pecuniary value on the militia which the inhabitants of the provinces, village by village, had been accustomed to furnish, ordering the collectors of his tribute to demand eighty pieces of gold for every soldier, although he had never before lightened the public burdens. This change was the origin of many disasters to the Roman empire subsequently.