With this account, which Strabo seems to prefer, agrees tolerably well that of Justin, who says that "Arsaces, having been long accustomed to live by robbery and rapine, attacked the Parthians with a predatory band, killed their satrap, Andragoras, and seized the supreme authority." As there was in all probability a close ethnic connection between the Dahae and the Parthians, it would be likely enough that the latter might accept for a king a chieftain of the former who had boldly entered their country, challenged the Greek satrap to an encounter, and by defeating and killing him freed them--at any rate for the time--from the Greek yoke.
An oppressed people gladly adopts as chief the head of an allied tribe if he has shown skill and daring, and offers to protect them from their oppressors.
The revolt of Arsaces has been placed by some as early as the year B.C.
256.

The Bactrian revolt is assigned by most historians to that year; and the Parthian, according to some, was contemporary.

The best authorities, however, give a short interval between the two insurrections; and, on the whole, there is perhaps reason to regard the Parthian independence as dating from about B.C.250.

This year was the eleventh of Antiochus Theus, and fell into the time when he was still engaged in his war with Ptolemy Philadelphus.

It might have been expected that when he concluded a peace with the Egyptian monarch in B.C.249, he would have turned his arms at once towards the east, and have attempted at any rate the recovery of his lost dominions.