Written by Strabo circa 7 BC
As for the Parthian country, it is not large; at any rate, it paid its tribute along with the Hyrcanians in the Persian times, and also after this, when for a long time the Macedonians held the mastery. And, in addition to its smallness, it is thickly wooded and mountainous, and also poverty-stricken, so that on this account the kings send their own throngs through it in great haste, since the country is unable to support them even for a short time. At present, however, it has increased in extent. Parts of the Parthian country are Comisenê and Chorenê, and, one may almost say, the whole region that extends as far as the Caspian Gates and Rhagae and the Tapyri, which formerly belonged to Media. And in the neighborhood of Rhagae are the cities Apameia and Heracleia. The distance from the Caspian Gates to Rhagae is five hundred stadia, as Apollodorus says, and to Hecatompylus, the royal seat of the Parthians, one thousand two hundred and sixty. Rhagae is said to have got its name from the earthquakes that took place in that country, by which numerous cities and two thousand villages, as Poseidonius says, were destroyed. The Tapyri are said to live between the Derbices and the Hyrcanians. It is reported of the Tapyri that it was a custom of theirs to give their wives in marriage to other husbands as soon as they had had two or three children by them; just as in our times, in accordance with an ancient custom of the Romans, Cato gave Marcia in marriage to Hortensius at the request of the later.
But when revolutions were attempted by the countries outside the Taurus, because of the fact that the kings of Syria and Media, who were in possession also of these countries, were busily engaged with others, those who had been entrusted with their government first caused the revolt of Bactriana and of all the country near it, I mean Euthydemus and his followers; and then Arsaces, a Scythian, with some of the Däae (I mean the Aparnians, as they were called, nomads who lived along the Ochus), invaded Parthia and conquered it. Now at the outset Arsaces was weak, being continually at war with those who had been deprived by him of their territory, both he himself and his successors, but later they grew so strong, always taking the neighboring territory, through successes in warfare, that finally they established themselves as lords of the whole country inside the Euphrates. And they also took a part of Bactriana, having forced the Scythians, and still earlier Eucratides and his followers, to yield to them; and at the present time they rule over so much land and so many tribes that in the size of their empire they have become, in a way, rivals of the Romans. The cause of this is their mode of life, and also their customs, which contain much that is barbarian and Scythian in character, though more that is conducive to hegemony and success in war.
They say that the Aparnian Däae were emigrants from the Däae above Lake Maeotis, who are called Xandii or Parii. But the view is not altogether accepted that the Däae are a part of the Scythians who live about Maeotis. At any rate, some say that Arsaces derives his origin from the Scythians, whereas others say that he was a Bactrian, and that when in flight from the enlarged power of Diodotus and his followers he caused Parthia to revolt. The Council of the Parthians, according to Poseidonius, consists of two groups, one that of kinsmen, and the other that of wise men and Magi, from both of which groups the kings were appointed.