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 therefo