When Isdigerd had reigned peaceably for the space of nine years, he is said to have received a compliment of an unusual character. Arcadius, the emperor of the East, finding his end approaching, and anxious to secure a protector for his son Theodosius, a boy of tender age, instead of committing him to the charge of his uncle Honorius, or selecting a guardian for him from among his own subjects, by a formal testamentary act, we are told, placed his child under the protection of the Persian monarch. He accompanied the appointment by a solemn appeal to the magnanimity of Isdigerd, whom he exhorted at some length to defend with all his force, and guide with his best wisdom, the young king and his kingdom. According to one writer, he further appended to this trust a valuable legacy--no less than a thousand pounds weight of pure gold, which he begged his Persian brother to accept as a token of his goodwill. When Arcadius died, and the testament was opened, information of its contents was sent to Isdigerd, who at once accepted the charge assigned to him, and addressed a letter to the Senate of Constantinople, in which he declared his determination to punish any attempt against his ward with the extremest severity. Unable to watch over his charge in person, he selected for his guide and instructor a learned eunuch of his court, by name Antiochus, and sent him to Constantinople, where for several years he was the young prince's constant companion. Even after his death or expulsion, which took place in consequence of the intrigues of Pulcheria, Theodosius's elder sister, the Persian monarch continued faithful to his engagements. During the whole of his reign he not only remained at peace with the Romans, but avoided every act that they could have regarded as in the least degree unfriendly.
Such is the narrative which has come down to us on the authority of historians, the earliest of whom wrote a century and a half after Arcadius's death. Modern criticism has, in general, rejected the entire story, on this account, regarding the silence of the earlier writers as outweighing the positive statements of the later ones. It should, however, be borne in mind, first that the earlier writers are few in number, and that their histories are very meagre and scanty; secondly, that the fact, if fact it were, was one not very palatable to Christians; and thirdly, that, as the results, so far as Rome was concerned, were negative, the event might not have seemed to be one of much importance, or that required notice. The character of Procopius, with whom the story originates, should also be taken into consideration, and the special credit allowed him by Agathias for careful and diligent research. It may be added, that one of the main points of the narrative--the position of Antiochus at Constantinople during the early years of Theodosius--is corroborated by the testimony of a contemporary, the bishop Synesius, who speaks of a man of this name, recently in the service of a Persian, as all-powerful with the Eastern emperor. It has been supposed by one writer that the whole story grew out of this fact; but the basis scarcely seems to be sufficient; and it is perhaps most probable that Arcadius did really by his will commend his son to the kind consideration of the Persian monarch, and that that monarch in consequence sent him an adviser, though the formal character of the testamentary act, and the power and position of Antiochus at the court of Constantinople, may have been overstated. Theodosius no doubt owed his quiet possession of the throne rather to the good disposition towards him of his own subjects than to the protection of a foreigner; and Isdigerd refrained from all attack on the territories of the young prince, rather by reason of his own pacific temper than in consequence of the will of Arcadius.