But circumstances which we cannot exactly trace determined his choice differently.

While Eucratidas was entangled in his Indian wars, Mithridates invaded the Bactrian territory where it adjoined Parthia, and added to his Empire, after a short struggle, two provinces, called respectively Turiua and that of Aspionus.

It is conjectured that these provinces lay towards the north and the north-west, the one being that of the Turanians proper, and the other that of the Aspasiacae, who dwelt between the Jaxartes and the Oxus.

But there is scarcely sufficient ground for forming even a conjecture on the subject, since speculation has nothing but the names themselves to rest upon.
Successful in this quarter, Mithridates, a few years later, having waited until the Syrian throne was occupied by the boy Eupator, and the two claimants of the regency, Lysias and Philip, were contending in arms for the supreme power, made suddenly an expedition towards the west, falling upon Media, which, though claimed by the Syrian kings as a province of their Empire, was perhaps at this time almost, if not quite, independent.

The Medes offered a vigorous resistance to his attack; and, in the war which followed, each side had in turn the advantage; but eventually the Parthian prince proved victorious, and the great and valuable province of Media Magna was added to the dominons of the Arsacidae.