Arsaces Iii. Tiranus
the son of Diran (Tiridates III.), ascended the throne either in the seventeenth year of the reign of Constantius, that is, in A. D. 354, or perhaps as early as 341 or 342, after his father had been made prisoner and deprived of his sight by Sapor II., king of Persia.
After the reconciliation of Sapor with his captive Diran (Tiridates), Arsaces was chosen king, since his father, on account of his blindness, was unable to reign according to the opinion of the eastern nations, which opinion was also entertained by the Greeks of the Lower Empire, whence we so often find that when an emperor or usurper succeeded in making his rival prisoner, he usually blinded him, if he did not venture to put him to death.
The nomination of Arsaces was approved by the emperor Constantius.
The new king nevertheless took the part of Sapor in his war with the Romans, but soon afterwards made peace with the latter.
He promised to pay an annual tribute, and Constantius allowed him to marry Olympias, the daughter of the praefect Ablavius, a near relation of the empress Constantia, and who had been betrothed to Constans, the brother of Constantius. Olympias was afterwards poisoned by a mistress of Sapor, an Armenian princess of the name of P'harhandsem.
To punish the defection of Arsaces, Sapor invaded Armenia and took Tigranocerta.
He was thus involved in a war with the emperor Julian, the successor of Constantius, who opened his famous campaign against the Persians (A. D. 363) in concert with Arsaces, on whose active co-operation the success of the war in a great measure depended. But Julian's sanguine expectations of overthrowing the power of the Sassanidae was destroyed by the pusillanimity, or more probably well calculated treachery, of Arsaces, who withdrew his troops from the Roman camp near Ctesiphon in the month of June, 363. Thence the disastrous retreat of the Romans and the death of Julian, who died from a wound on the 26th of the same month. Jovian, who was chosen emperor in the camp, saved the Roman army by a treaty in July, by which he renounced his sovereignty over the tributary kingdoms of Armenia and Iberia. Arsaces, in the hope of receiving the reward of his treachery, ventured into the camp of Sapor.
He was at first received with honour, but in the midst of an entertainment was seized by order of Sapor and confined in the tower of Oblivion at Ecbatana, where he was loaded with silver chains.
He died there by the land of a faithful servant, whom he implored to release him with his sword from the humiliation of his captivity. Arsaces reigned tyrannically, and had a strong party against him, especially among the nobles. (Amm. Marc. 20.11
; Procop. de Bell. Pers.