is variously represented by the ancient writers as a Scythian, a Bactrian, or a Parthian. (Strab. xi. p.515; Arrian, apud Phot. Cod. 58, p. 17, ed. Bekker; Herodian, 6.2; Moses Chor. 1.7.) Justin (41.4) says, that he was of uncertain origin. He seems however to have been of the Scythian race, and to have come from the neighbourhood of the Ochus, as Strabo says (l.c.), that he was accompanied in his undertaking by the Parni Daae, who had migrated from the great race of the Scythian Daae, dwelling above the Palus Maeotis, and who had settled near the Ochus. But from whatever country the Parthians may have come, they are represented by almost all ancient writers as Scythians. (Curt. 6.2; Justin, 41.1; Plut. Crass. 24; Isidor. Orig. 9.2.) Arsaces, who was a man of approved valour, and was accustomed to live by robbery and plunder, invaded Parthia with his band of robbers, defeated Andragoras, the governor of the country, and obtained the royal power. This is the account given by Justin (l.c.), which is in itself natural and probable, but different from the common one which is taken from Arrian. According to Arrian (apud Phot. Cod. 58), there were two brothers, Arsaces and Tiridates, the descendants of Arsaces, the son of Phriapitus. Pherecles, the satrap of Parthia in the reign of Antiochus II., attempted to violate Tiridates, but was slain by him and his brother Arsaces, who induced the Parthians in consequence to revolt from the Syrians. The account of Arrian in Syncellus (p. 284) is again different from the preceding one preserved by Photius; but it is impossible to determine which has given us the account of Arrian most faithfully. According to Syncellus, Arrian stated that the two brothers Arsaces and Tiridates, who were descended from Artaxerxes, the king of the Persians, were satraps of Bactria at the same time as the Macedonian Agathocles governed Persia (by which he means Parthia) as Eparch. Agathocles had an unnatural passion for Tiridates, and was slain by the two brothers. Arsaces then became king, reigned two years, and was succeeded by his brother Tiridates, who reigned 37 years.

The time, at which the revolt of Arsaces took place, is also uncertain. Appian (App. Syr. 65) places it at the death of Antiochus II., and others in the reign of his successor, Seleucus Callinicus. According to the statement of Arrian quoted above, the revolt commenced in the reign of Antiochus II., which is in accordance with the date given by Eusebius, who fixes it at B. C. 250, and which is also supported by other authorities. (Clinton, F. H. vol. iii. sub anno 250.) Justin (41.4, 5), who is followed in the main by Ammianus Marcellinus (23.6), ascribes to Arsaces I. many events, which probably belong to his successor. According to his account Arsaces first conquered Hyrcania, and then prepared to make war upon the Bactrian and Syrian kings. He concluded, however, a peace with Theodotus, king of Bactria, and defeated Seleucus Callinicus, the successor of Antiochus II. in a great battle, the anniversary of which was ever after observed by the Parthians, as the commencement of their liberty. According to Posidonius (apud Athen. iv. p. 153a.), Seleucus was taken prisoner in a second expedition which he made against the Parthians, and detained in captivity by Arsaces for many years. After these events Arsaces devoted himself to the internal organization of his kingdom, built a city, called Dara, on the mountain Zapaortenon, and died in a mature old age. This account is directly opposed to the one given by Arrian, already referred to (apud Syncell.l.c.), according to which Arsaces was killed after a reign of two years and was succeeded by his brother. Arrian has evidently confounded Arsaces I. and II., when he says that the former was succeeded by his son. This statement we must refer to Arsaces II.