Here Arsaces and his brother Tiridates are derived from the royal house of the Achaemenids, probably from Artaxerxes II.; the young Tiridates is insulted by the prefect Agathocles or Pherecles; in revenge the brothers with five companions (corresponding to the seven Persians of Darius) slay him, and Arsaces becomes king.
But this historical aspect of the myth is of late origin: it is nothing but a reflex of the great Iranian empire founded by the Achaemenids and restored by the Sassanids.
On the contrary, it is historically evident that before the Achaemenids there were in Bactria only small local principalities of which Vishtaspas was one:
Their institutions, court ceremonial and dress were all adopted by the Achaemenids.
There existed, in fact, under the Achaemenids a strong colonizing movement, diffused through the whole empire; traces of this policy occur more especially in Armenia, Cappadocia and, Lycia, but also in the rest of Asia Minor, and not rarely in Syria and Egypt.