PA'RTHIA originally comprised a small and mountainous country (Strabo,xL p. 514) south-east of the Caspian Sea, between Hyrcania and Aria; bat the name was sometimes applied to the countries Included in the later Parthian empire. It is difficult to define the boundaries of Parthia proper, as they differed at various times. In the time of Strabo (xi. 514) Parthia extended on the west as far as Magas and the Tapuri to the Caspian passes, and included the districts of Komisode (Kumla) and Choarene (Khuar). Pliny (vi. 29) says that it was bounded E. by the .Arii, S. by the Carmauil and Arinni, W. by the Pratitee Medi, and N. by the Hyreani.
The chief town of Parthia, and the only one in the country of any importance, was Ilecatompylon, which, according to Strabo (xi. 514), was 1260 stadia from the Caspian gates. The site of it is doubtfuL Some writers identify it with the modern Damghan.
The Parthians were apparently of Scythian origin. According to Justin Oa 1) their name signified in the Scythian language banished,' or exiles.' The l'arthians were subject to the Poreieu monarchy, and iu (Herod., iii. 93) the army of Xerxes they marched together with the Chorasmii, Sogdi, Ganderii, and Dadiere (Herod., vii. 97); and in that of the lest Darius they were united with the Hyrcanii and Tapuri under one commander (Arrian, iii. S). Under Alexander, Parthia and Hyrcania together formed a satrapy (iii. 22).
On the death of Alexander the Parthians espoused the side of Eumenes, and afterwards became subject successively to Autigonus and the Seleucidre, till about n.c. 256, when they threw off the authority of the Syrian kings and were formed into an independent kingdom under the rule of Arsaces I., from whom the succeeding kings received the title of Areacidre. His reign was the beginning of the great Parthian empire, which was gradually increased at the expense of the Syrian kingdom in the west and the Bactrian in the east ; and at length extended from the Euphrates to the Indus, and from the Oxus to the Persian Gulf.
The Parthian empire lasted from B.C. 256 to A.D. 226. Under Arsaces L, Mithridates I., and Phraates II. the dominions of Parthia were extended as far as the Euphrates and the Indus; after the defeat of Antiochus Sidetes of Syria in n.0.130, the Parthiane were constantly engaged in wars with the nomad tribes of central Asia, who, after the destruction of the Greek kingdom in Bactria, attempted to obtain possession of the western parts of Asia. Tigranes, king of Armenia, also obtained some successes over Mithridates IL, but after his conquest by the Romans the Parthians again acquired the ascendancy. The invasion of Cassius during the reign of Orodes terminated in the death of the Roman general and the destruction of his army, n.c. 53, and the Parthians obtained a great increase of power. In the war between Caesar and Pompey they took the side of Pompey; and after the death of Caesar they sided with Brutus and Cassius. In D.C. 37 Orodea was murdered by his son Phraates IV., and from this time the history of Parthia is a succession of civil ware, with occasional inter ventions by the Romans, until A.D. 217, when Artaxerxes, who had served with great reputation in the army of Artabenus, the last king of l'arthia, took advantage of the weakened state of the monarchy to found a new dynasty. He represented himself as n descendant of the ancient kings of Persia, and called upon the Persians to recover their independence. This call was readily responded to ; a large Persian army was collected; the Parthians were defeated in three great battles, and Artaxerxes succeeded to all the dominions of the Parthian kings, and became the founder of the new Persian empire, which is usually known by that of the Sassanidee.