year of Mithridates I, is "the first precisely established regnal date of Parthian history." Due to these and other discrepancies, Bivar outlines two distinct royal chronologies accepted by historians. A fictitious claim was later made from the 2nd-century BC onwards by the Parthians, which represented them as descendants of the Achaemenid king of kings, Artaxerxes II of Persia .

For a time, Arsaces I consolidated his position in Parthia and