for this last gift, which brought the Indian frontier still nearer than before to that of Bactria, At any rate, the result of the Indian expedition of Antiochus seems to have been unsatisfactory to Euthydemus, who shortly afterwards commenced what are called “Indian Wars” on his south-eastern frontier, employing in them chiefly the arms of his son, Demetrius.  During the latter years of Euthydemus and the earlier ones of Demetrius, the Bactrian rule was rapidly extended over the greater portion of the modern Afghanistan; nor did it even stop there.  The arms of Demetrius were carried across the Indus into the Punjaub region; and the city of Euthymedeia upon the Hydaspes remained to later times an evidence of the extent of his conquests.  From B.C. 206 to about B.C. 185 was the most flourishing period of the Bactrian monarchy, which expanded during that space from a small kingdom into a considerable empire.

The power and successes of the Bactrian princes at this time account sufficiently for the fact that the contemporary Parthian monarchs stood upon their guard, and undertook no great expeditions.  Arsaces III., who continued on the throne for about ten or twelve years after his peace with Antiochus, and Priapatius, or Arsaces IV., his son, who succeeded him, and had a reign of fifteen years, were content, as already observed, to watch over their own State, husbanding its resources, and living at peace with all their neighbors.  It was not till Phraates I.  (Arsaces V.), the son of Priapatius, had mounted the throne, B.C. 181, that this policy was departed from, and Parthia, which had remained tranquil for a quarter of a century, once more aroused herself, and assumed an attitude of aggression.

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.