It was naturally almost as hostile to Bactria as to Syria, although danger from a common enemy might cause it sometimes to make a temporary alliance with that kingdom.

It had, no doubt, the general sympathy of the populations in the adjacent countries, and represented to them the cause of freedom and autonomy.
The exact circumstances under which the Parthian revolt took place are involved in much obscurity.

According to one account the leader of the revolt, Arsaces, was a Bactrian, to whom the success of Diodotus was disagreeable, and who therefore quitted the newly-founded kingdom, and betook himself to Parthia, where he induced the natives to revolt and to accept him for their monarch.

Another account, which is attractive from the minute details into which it enters, is the following:--"Arsaces and Tiridates were brothers, descendants of Phriapites, the son of Arsaces.
Pherecles, who had been made satrap of their country by Antiochus Theus, offered a gross insult to one of them, whereupon, as they could not brook the indignity, they took five men into counsel, and with their aid slew the insolent one.

They then induced their nation to revolt from the Macedonians, and set up a government of their own, which attained to great power." A third version says that the Arsaces, whom all represent as the first king, was in reality a Scythian, who at the head of a body of Parnian Dahce, nomads inhabiting the valley of the Attrek (Ochus), invaded Parthia, soon after the establishment of Bactrian independence, and succeeded in making himself master of it.