This is evidenced not only by the grand claims which Artaxorxes put forward in his early negotiations with the Romans, but by the whole course of Persian literature, which has fundamentally an historic character, and exhibits the people as attached, almost more than any other Oriental nation, to the memory of its great men and of their noble achievements.
The countrymen of Cyrus, of Darius, of Xerxes, of Ochus, of the conquerors of Media, Bactria, Babylon, Syria, Asia Minor, Egypt, of the invaders of Scythia and Greece, aware that they had once borne sway over the whole region between Tunis and the Indian Desert, between the Caucasus and the Cataracts, when they saw a petty mountain clan, like the Hyrcanians, establish and maintain their independence despite the efforts of Parthia to coerce them, could not very well remain quiet.

If so weak and small a race could defy the power of the Arsacid monarchs, much more might the far more numerous and at least equally courageous Persians expect to succeed, if they made a resolute attempt to recover their freedom.
It is probable that Artaxerxes, in his capacity of vassal, served personally in the army with which the Parthian monarch Artabanus carried on the struggle against Rome, and thus acquired the power of estimating correctly the military strength still possessed by the Arsacidae, and of measuring it against that which he knew to belong to his nation.

It is not unlikely that he formed his plans during the earlier period of Artabanus's reign, when that monarch allowed himself to be imposed upon by Caracallus, and suffered calamities and indignities in consequence of his folly.

When the Parthian monarch atoned for his indiscretion and wiped out the memory of his disgraces by the brilliant victory of Nisibis and the glorious peace which he made with Macrinus, Artaxerxes may have found that he had gone too far to recede; or, undazzled by the splendor of these successes, he may still have judged that he might with prudence persevere in his enterprise.

Artabanus had suffered great losses in his two campaigns against Rome, and especially in the three days' battle of Nisibis.