The Ecclesiastical History Of Scholasticus by Socrates Scholasticus
Chapter XXV.--The Usurper Eugenius compasses the Death of Valentinian the Younger. Theodosius obtains a Victory over him.
There was in the Western regions a grammarian named Eugenius, who after having for some time taught the Latin language, left his school, and was appointed to service at the palace, being constituted chief secretary to the emperor. Possessing a considerable degree of eloquence, and being on that account treated with greater distinction than others, he was unable to bear his good fortune with moderation. For associating with himself Arbogastes, a native of Galatia Minor, who then had the command of a division of the army, a man harsh in manner and very bloodthirsty, he determined to usurp the sovereignty. These two therefore agreed to murder the Emperor Valentinian, having corrupted the eunuchs of the imperial bed-chamber. These, on receiving tempting promises of promotion, strangled the emperor in his sleep. Eugenius immediately assuming the supreme authority in the Western parts of the empire, conducted himself in such a manner as might be expected from a usurper. When the Emperor Theodosius was made acquainted with these things, he was exceedingly distressed, because his defeat of Maximus had only prepared the way for fresh troubles. He accordingly assembled his military forces, and having proclaimed his son Honorius Augustus, on the 10th of January, in his own third consulate which he bore with Abundantius, he again set out in great haste toward the Western parts, leaving both his sons invested with imperial authority at Constantinople. As he marched against Eugenius a very great number of the barbarians beyond the Danube volunteered their services, and followed him in this expedition. After a rapid march he arrived in the Gauls with a numerous army, where Eugenius awaited him, also at the head of an immense body of troops. Accordingly an engagement took place near the river Frigidus, which is [about thirty-six miles] distant [from Aquileia]. In that part of the battle where the Romans fought against their own countrymen, the conflict was doubtful: but where the barbarian auxiliaries of the Emperor Theodosius were engaged, the forces of Eugenius had greatly the advantage. When the emperor saw the barbarians perishing, he cast himself in great agony upon the ground, and invoked the help of God in this emergency: nor was his request unheeded; for Bacurius his principal officer, inspired with sudden and extraordinary ardor, rushed with his vanguard to the part where the barbarians were hardest pressed, broke through the ranks of the enemy, and put to flight those who a little before were themselves engaged in pursuit. Another marvelous circumstance also occurred. A violent wind suddenly arose, which retorted upon themselves the darts cast by the soldiers of Eugenius, and at the same time drove those hurled by the imperial forces with increased impetus against their adversaries. So prevalent was the emperor's prayer. The success of the struggle being in this way turned, the usurper threw himself at the emperor's feet, and begged that his life might be spared: but as he lay a prostrate suppliant at the feet [of the emperor] he was beheaded by the soldiers, on the 6th of September, in the third consulate of Arcadius, and the second of Honorius. Arbogastes, who had been the chief cause of so much mischief, having continued his flight for two days after the battle, and seeing no chance of escape, despatched himself with his own sword.