The quarter to which Phraates I. directed his arms was the country of the Mardians, a poor but warlike people, who appear to have occupied a portion of the Elburz range, probably that immediately south of Mazanderan and Asterabad. The reduction of these fierce mountaineers is likely to have occupied him for some years, since their country was exceedingly strong and difficult. Though the Mardi were (nominally, at any rate) subjects of the Seleucidae, we do not hear of any assistance being rendered them, or, indeed, of any remonstrance being made against the unprovoked aggression of the Parthian monarch. The reign of Phraates I. in Parthia coincides with that of Seleucus IV. (Philopator) in Syria; and we may account for the inactivity of this prince, in part by his personal character, which was weak and pacific, in part by the exhaustion of Syria at the time, in consequence of his father’s great war with Rome (B.C. 197-190), and of the heavy contribution which was imposed upon him at the close of it. Syria may scarcely have yet recovered sufficient strength to enter upon a new struggle, especially one with a distant and powerful enemy. The material interests of the Empire may also have seemed to be but little touched by the war, since the Mardi were too poor to furnish much tribute; and it is possible, if not even probable, that their subjection to Syria had long been rather formal than real. Seleucus therefore allowed the Mardians to be reduced, conceiving, probably, that their transfer to the dominion of the Arsacidse neither increased the Parthian power nor diminished his own.