At any rate, he ruled so harshly and cruelly that within a few years of his accession the Parthian nobles deposed him, and, recalling Orodes from his place of exile, set him up as king in his brother's room.

Mithridates was, it would seem, at first allowed to govern Media as a subject monarch; but after a while his brother grew jealous of him, and deprived him of this dignity.

Unwilling to acquiesce in his disgrace, Mithridates fled to the Romans, and being favorably received by Gabinius, then proconsul of Syria, endeavored to obtain his aid against his countrymen.

Gabinius, who was at once weak and ambitious, lent a ready ear to his entreaties, and was upon the point of conducting an expedition into Parthia, when he received a still more tempting invitation from another quarter.

Ptolemy Auletes, expelled from Egypt by his rebellious subjects, asked his aid, and having recommendations from Pompey, and a fair sum of ready money to disburse, found little difficulty in persuading the Syrian proconsul to relinquish his Parthian plans and march the force at his disposal into Egypt.
Mithridates, upon this, withdrew from Syria, and re-entering the Parthian territory, commenced a civil war against his brother, finding numerous partisans, especially in the region about Babylon.