Arsaces, king of Armenia, though placed on his throne by Sapor, had (as we have seen) transferred his allegiance to Constantius, and voluntarily taken up the position of a Roman feudatory.

Constantius had of late suspected his fidelity; but Arsaces had not as yet, by any overt act, justified these suspicions, and Julian seems to have regarded him as an assured friend and ally.
Early in A.D.363 he addressed a letter to the Armenian monarch, requiring him to levy a considerable force, and hold himself in readiness to execute such orders as he would receive within a short time.

The style, address, and purport of this letter were equally distasteful to Arsaces, whose pride was outraged, and whose indolence was disturbed, by the call thus suddenly made upon him.

His own desire was probably to remain neutral; he felt no interest in the standing quarrel between his two powerful neighbors; he was under obligations to both of them; and it was for his advantage that they should remain evenly balanced.

We cannot ascribe to him any earnest religious feeling; but, as one who kept up the profession of Christianity, he could not but regard with aversion the Apostate, who had given no obscure intimation of his intention to use his power to the utmost in order to sweep the Christian religion from the face of the earth.