<P> The Achaemenid line would be carried on through the Kingdom of Pontus, based in the Pontus region of northern Asia Minor . This Pontic Kingdom, a state of Persian origin, may even have been directly related to Darius the Great and the Achaemenid dynasty . It was founded by Mithridates I in 281 BC and lasted until its conquest by the Roman Republic in 63 BC . The kingdom grew to its largest extent under Mithridates VI the Great, who conquered Colchis, Cappadocia, Bithynia, the Greek colonies of the Tauric Chersonesos and for a brief time the Roman province of Asia . Thus, this Persian dynasty managed to survive and prosper in the Hellenistic world while the main Persian Empire had fallen . </P> <P> Both the later dynasties of the Parthians and Sasanians would on occasion claim Achaemenid descent . Recently there has been some corroboration for the Parthian claim to Achaemenid ancestry via the possibility of an inherited disease (neurofibromatosis) demonstrated by the physical descriptions of rulers and from evidence of familial disease on ancient coinage . </P> <P> Part of the cause of the Empire's decline had been the heavy tax burden put upon the state, which eventually led to economic decline . An estimate of the tribute imposed on the subject nations was up to U.S. $180 M per year . This does not include the material goods and supplies that were supplied as taxes . After the high overhead of government--the military, the bureaucracy, whatever the satraps could safely dip into the coffers for themselves--this money went into the royal treasury . According to Diodorus, at Persepolis, Alexander III found some 180,000 Attic talents of silver besides the additional treasure the Macedonians were carrying that already had been seized in Damascus by Parmenion . This amounted to U.S. $2.7 B. On top of this, Darius III had taken 8,000 talents with him on his flight to the north . Alexander put this static hoard back into the economy, and upon his death some 130,000 talents had been spent on the building of cities, dockyards, temples, and the payment of the troops, besides the ordinary government expenses . Additionally, one of the satraps, Harpalus, had made off to Greece with some 6,000 talents, which Athens used to rebuild its economy after seizing it during the struggles with the Corinthian League . Due to the flood of money from Alexander's hoard entering Greece, however, a disruption in the economy occurred, in agriculture, banking, rents, the great increase in mercenary soldiers that cash allowed the wealthy, and an increase in piracy . </P> <P> Another factor contributing to the decline of the Empire, in the period following Xerxes, was its failure to ever mold the many subject nations into a whole; the creation of a national identity was never attempted . This lack of cohesion eventually affected the efficiency of the military . </P>

How did economic decline lead to the collapse of the achaemenid dynasty
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