Roman emperor A. D. 375-392, a son of Valentinianus I., was with his mother Justina, about one hundred miles from the camp of Bregetio, when his father died there, A. D. 375. His brother Gratianus was at Trèves. Valentinian and his mother were summoned to Bregetio, when the army proclaimed Valentinian, Augustus, six days after his father's death. He was then only four or five years of age ; and Gratian was only about seventeen. Gratian assented to the choice of the army, and a division of the West was made between the two brothers Valentinian had Italy, Illyricum and Africa. Gratian had the Gauls, Spain and Britain. This division, however, if it actually took place, was merely nominal. and Gratian as long as he lived was actually emperor of the West. One reason for supposing that Gratian really retained all the imperial power is the fact, that after the death of Valens, and in A. D. 379 Gratian ceded a part of Illyricum to Theodosius I., whom he declared emperor of the East. This seems to show at least that the division of the empire of the West between Gratian and Valentinian was not completed at the time when Theodosius received a part of Illyricum.

In A. D. 383, Gratian was murdered at Lyon. [GRATIANUS; THEODOSIUS I.] Milan was the chief residence of Valentinian II. from the time of his father's death, and he was in this city during A. D. 384. He made Symmachus prefect of Rome, probably about the close of A. D. 383. Valentinian was still at Milan in the first half of A. D. 386, and afterwards at Aquileia. His mother Justina, who acted in his name, and was an Arian, employed herself in persecuting the Catholics during this and the following year. In A. D. 386, Valentinian addressed a letter to Sallustius, the prefect of Rome, in which he ordered him to rebuild the church of St. Paul, near Rome, on the road to Ostia. The church was rebuilt, but apparently somewhat later than the time of this order.

Maximius, who had usurped the throne of Gratian, left Valentinian a precarious authority out of fear for Theodosius I. : but in August, A. D. 387, he suddenly crossed the Alps, and advanced towards Milan, the usual residence of Valentinian. The emperor and his mother fled to the Hadriatic, where they took shipping and arrived at Thessalonica. In A. D. 388, Theodosius defeated Maximus, and restored Valentinian to his authority as emperor of the West. [THEODOSIUS I.] In A. D. 389, Valentinian went into Gaul to conduct operations against the Franks on the Rhine. Arbogast was at that time commander of the Roman forces in Gaul. Nothing further is recorded of this campaign, except that Valentinian had a conference with Marcomir and Sunnon, the chiefs of the Franks, who gave him hostages. Valentinian spent the winter at Trèves, as appears from a constitution dated the 8th of November.

Tillemont remarks, " that Theodosius, who spent about three years in Italy, after the defeat of Maximus, had by his wise advice effaced from the mind of the youthful emperor all the bad impressions which his mother Justina had fixed in him against the faith and St. Ambrose, and forming himself after the example of Theodosius, he had a fervent devotion towards God, and loved St. Ambrose with such affection, that he cherished him as much as he had formerly persecuted him." In A. D. 391, Q. Aurelius Symmachus, who was consul with Tatianus, was the head of a deputation from the Roman senate to Valentinian, the object of which was to ask of the emperor the restoration of the privileges which Gratian had taken from the temples of the idols. The emperor however positively refused to grant the petition.

At this time, the barbarians were in motion, on the side of the Illyrian Alps, and it was apprehended that they might disturb Italy. Valentinian set out for Italy, with the intention of going to Milan. He was at Vienna (Vienne), when he sent for Ambrosius to baptize him before he entered Italy, for he was yet only a catechumen. There were many bishops in France, but Valentinian wished to receive this Christian rite at the hands of Ambrose. "After having written to Ambrose, he passed the two following days in such inquietude and such impatience to see the saint, that having despatched a courier in the evening, he asked on the morning of the third day, which was the last of his life, if the courier had not returned, and if the saint was not coming." (Tillemont.)

Arbogast, a Frank by origin, a man probably of violent temper, though on this point there is a difference in the testimony, but a rude soldier and a man of courage and address, was aiming at governing Valentinian, who was still a youth. Gratian employed Arbogast and sent him in A. D. 381 under Bauton to assist Theodosius who was pressed by the Goths. After the death of Bauton, Arbogast assumed the command of the troops without, it is said, waiting for the orders of Valentinian. During the usurpation of Maximus, Arbogast was faithful to his master, and contributed greatly to the overthrow of Maximus. Presuming however on his abilities, his influence with the army, and the youth of Valentinian, Arbogast kept the emperor in a kind of tutelage, of which Valentinian complained to Theodosius. At last the emperor mustered courage to give into the hands of Arbogast a written order by which he was deprived of his military rank; but the proud soldier told his to his face, that he had not given him his office and that it was not in his power to take it away. With these words he tore the writing, threw it on the ground, and quitted the emperor's presence.

There are different accounts of the death of Valentinian. The most probable is, that he was strangled by order of Arbogast. His body was taken to Milan for interment by the side of his father, and Ambrose pronounced the funeral oration. Valentinian II. died on the 15th of May, being only a few months above twenty years of age. Justa and Grata, the two sisters of Valentinian, deplored with sincere affection the untimely end of their brother. " Ambrose, who was so well instructed in the doctrine of the church, does not hesitate in his funeral oration to assure us of the salvation of a prince, who had not received the sacrament of salvation, but had asked for it, and was disposed to receive it." (Tillemont.) On this point, see Gibbon, 100.27. note 108.

Justina, the mother of Valentinian, was dead ; she had not long survived the restoration of her son to his throne, and her influence expired before she died. Justa and Grata, the sisters of the emperor, remained unmarried; and Galla, the wife of Theodosius, who deeply lamented her brother's death, died in A. D. 394, in childbed, when Theodosius was leaving Constantinople to avenge the death of Valentinian.

The reign of Valentinian is of little importance ; and what concerns the Roman legislation of this period belongs to the history of Theodosius I.

(Gibbon, Decline and Fall, &c.; Tillemont, Histoire des Empereurs, v., where the authorities are collected.)