The ambition of the Persian, to whom his enemies ascribe the virtues of a soldier and a statesman, was animated by the desire of revenging the disgrace of his fathers, and of wresting from the hands of the Romans the five provinces beyond the Tigris. The military fame of Constantine, and the real or apparent strength of his government, suspended the attack; and while the hostile conduct of Sapor provoked the resentment, his artful negotiations amused the patience of the Imperial court. The death of Constantine was the signal of war, and the actual condition of the Syrian and Armenian frontier seemed to encourage the Persians by the prospect of a rich spoil and an easy conquest. The example of the massacres of the palace diffused a spirit of licentiousness and sedition among the troops of the East, who were no longer restrained by their habits of obedience to a veteran commander. By the prudence of Constantius, who, from the interview with his brothers in Pannonia, immediately hastened to the banks of the Euphrates, the legions were gradually restored to a sense of duty and discipline; but the season of anarchy had permitted Sapor to form the siege of Nisibis, and to occupy several of the most important fortresses of Mesopotamia. In Armenia, the renowned Tiridates had long enjoyed the peace and glory which he deserved by his valor and fidelity to the cause of Rome. The firm alliance which he maintained with Constantine was productive of spiritual as well as of temporal benefits; by the conversion of Tiridates, the character of a saint was applied to that of a hero, the Christian faith was preached and established from the Euphrates to the shores of the Caspian, and Armenia was attached to the empire by the double ties of policy and religion. But as many of the Armenian nobles still refused to abandon the plurality of their gods and of their wives, the public tranquillity was disturbed by a discontented faction, which insulted the feeble age of their sovereign, and impatiently expected the hour of his death. He died at length after a reign of fifty-six years, and the fortune of the Armenian monarchy expired with Tiridates. His lawful heir was driven into exile, the Christian priests were either murdered or expelled from their churches, the barbarous tribes of Albania were solicited to descend from their mountains; and two of the most powerful governors, usurping the ensigns or the powers of royalty, implored the assistance of Sapor, and opened the gates of their cities to the Persian garrisons. The Christian party, under the guidance of the Archbishop of Artaxata, the immediate successor of St. Gregory the Illuminator, had recourse to the piety of Constantius. After the troubles had continued about three years, Antiochus, one of the officers of the household, executed with success the Imperial commission of restoring Chosroes, * the son of Tiridates, to the throne of his fathers, of distributing honors and rewards among the faithful servants of the house of Arsaces, and of proclaiming a general amnesty, which was accepted by the greater part of the rebellious satraps. But the Romans derived more honor than advantage from this revolution. Chosroes was a prince of a puny stature and a pusillanimous spirit. Unequal to the fatigues of war, averse to the society of mankind, he withdrew from his capital to a retired palace, which he built on the banks of the River Eleutherus, and in the centre of a shady grove; where he consumed his vacant hours in the rural sports of hunting and hawking. To secure this inglorious ease, he submitted to the conditions of peace which Sapor condescended to impose; the payment of an annual tribute, and the restitution of the fertile province of Atropatene, which the courage of Tiridates, and the victorious arms of Galerius, had annexed to the Armenian monarchy.

During the long period of the reign of Constantius, the provinces of the East were afflicted by the calamities of the Persian war. The irregular incursions of the light troops alternately spread terror and devastation beyond the Tigris and beyond the Euphrates, from the gates of Ctesiphon to those of Antioch; and this active service was performed by the Arabs of the desert, who were divided in their interest and affections; some of their independent chiefs being enlisted in the party of Sapor, whilst others had engaged their doubtful fidelity to the emperor. The more grave and important operations of the war were conducted with equal vigor; and the armies of Rome and Persia encountered each other in nine bloody fields, in two of which Constantius himself commanded in person. The event of the day was most commonly adverse to the Romans, but in the battle of Singara, heir imprudent valor had almost achieved a signal and decisive victory. The stationary troops of Singara * retired on the approach of Sapor, who passed the Tigris over three bridges, and occupied near the village of Hilleh an advantageous camp, which, by the labor of his numerous pioneers, he surrounded in one day with a deep ditch and a lofty rampart. His formidable host, when it was drawn out in order of battle, covered the banks of the river, the adjacent heights, and the whole extent of a plain of above twelve miles, which separated the two armies. Both were alike