But the intention of Tiridates, if we have truly defined it, failed of taking permanent effect.

He may himself have fixed his abode at Dara, but his successors did not inherit his predilections; and Hecatompylos remained, after his reign, as before it, the head-quarters of the government, and the recognized metropolis of Parthia Proper.
After passing in peace and prosperity the last twenty years of his reign, Tiridates died in a good old age, leaving his crown to a son, whose special name is a little uncertain, but who is called by most moderns Artabanus I.
Artabanus, having ascended the Parthian throne about B.C.214, and being anxious to distinguish himself, took advantage of the war raging between Antiochus III., the second son of Seleucus Callinicus, and Achseus, one of his rebel satraps, to advance into Media, and to add to his dominions the entire tract between Hyrcania and the Zagros mountains.

Of the manner in which he effected his conquests we have no account; but they seem to have been the fruit of a single campaign, which must have been conducted with great vigor and military skill.

The Parthian prince appears to have occupied Ecbatana, the ancient capital of the Median Empire, and to have thence threatened the Mesopotamian countries.

Upon receiving intelligence of his invasion, Antiochus levied a vast army, and set out towards the East, with a determination to subjugate all the revolted provinces, and to recover the limits of the old Empire of Nicator.