Revolt of Armenia and Acceptance by Arsaces of the Position of a Roman Feudatory.  Character and Issue of Sapor’s Eastern Wars.  His negotiations with Constantius.  His Extreme Demands.  Circumstances under which he determines to renew the War.  His Preparations.  Desertion to him of Antoninus.  Great Invasion of Sapor.  Siege of Amida.  Sapor’s Severities.  Siege and Capture of Singara; of Bezabde.  Attack on Virtu fails.  Aggressive Movement of Constantius.  He attacks Bezabde, but fails Campaign of A.D. 361.  Death of Constantius.

Evenerat . . . quasi fatali constellatione . . . ut Constantium dimicantem cum Persis fortuna semper sequeretur afflictior.—­Amm.  Marc. xx. 9, ad fin.

It seems to have been soon after the close of Sapor’s first war with Constantius that events took place in Armenia which once more replaced that country under Roman influence.  Arsaces, the son of Tiranus, had been, as we have seen, established as monarch, by Sapor, in the year A.D. 341, under the notion that, in return for the favor shown him, he would administer Armenia in the Persian interest.  But gratitude is an unsafe basis for the friendships of monarchs.  Arsaces, after a time, began to chafe against the obligations under which Sapor had laid him, and to wish, by taking independent action, to show himself a real king, and not a mere feudatory.  He was also, perhaps, tired of aiding Sapor in his Roman war, and may have found that he suffered more than he gained by having Rome for an enemy.  At any rate, in the interval between A.D. 351 and 359, probably while Sapor was engaged in the far East, Arsaces sent envoys to Constantinople with a request to Constantius that he would give him in marriage a member of the Imperial house.  Constantius was charmed with the application made to him, and at once accepted the proposal.  He selected for the proffered honor a certain Olympias, the daughter of Ablabius, a Praetorian prefect, and lately the betrothed bride of his own brother, Constans; and sent her to Armenia, where Arsaces welcomed her, and made her (as it would seem) his chief wife, provoking thereby the jealousy and aversion of his previous sultana, a native Armenian, named Pharandzem.  The engagement thus entered into led on, naturally, to the conclusion of a formal alliance between Rome and Armenia—­an alliance which Sapor made fruitless efforts to disturb, and which continued unimpaired down to the time A.D. 359 when hostilities once more broke out between Rome and Persia.

Of Sapor’s Eastern wars we have no detailed account.  They seem to have occupied him from A.D. 350 to A.D. 357, and to have been, on the whole, successful.  They were certainly terminated by a peace in the last-named year—­a peace of which it must have been a condition that his late enemies should lend him aid in the struggle which he was about to renew with Rome.  Who these enemies exactly were, and what exact region they inhabited, is doubtful.  They comprised certainly the Chionites