According to Diodorus, who probably followed Ctesias, they passed from the dominion of the Assyrians to that of the Medes, and from dependence upon the Medes to a similar position under the Persians.

But the balance of evidence is against these views.

It is, on the whole, most probable that neither the Assyrian nor the Median empire extended so far eastward as the country of the Parthians.

The Parthians probably maintained their independence from the time of their settlement in the district called after their name until the sudden arrival in their country of the great Persian conqueror, Cyrus.

This prince, as Herodotus tells us, subdued the whole of Western Asia, proceeding from nation to nation, and subjugating one people after another.