From that time on, Arsaces changed his policy: he acted no longer as a nomad but rather as a chief of state—a worthy successor to the Seleucids, whose example he followed, in Parthia. He had himself crowned. Besides Asaak and Dārā (an impregnable fortress), he founded such cities as Nisā, where he would be buried. These new cities were usually named for the king or the dynasty. Arsaces seems not to have infringed on the rights of the Greeks and Macedonians living in these cities, perhaps hoping to win their support. From the beginning, while maintaining the autonomy of the cities, he made use of propaganda to ensure their continuing obedience. He installed his capital at Hecatompylos, on the Silk Road. His death is dated between 217 and 211 bc. Artabanus I
Arsaces’ successor, Artabanus I (reigned c. 211–191 bc), sometimes known as Arsaces II, continued the work of consolidation. Artabanus, already solidly established in Parthia and Hyrcania, tried to extend his possessions toward Media. But events in the neighbouring Greco-Bactrian kingdom worked against him: Diodotus II (accused, it is thought, of treason to Hellenism through his alliance with the nomads) lost his throne, which passed to Euthydemus by the time the Syrian army of the Seleucid king Antiochus III (the Great) arrived in Hyrcania.
The wave of revolts by the eastern satraps, which began a movement away from unity in the state, also affected western Iran; the beginning of the reign of Antiochus (223–187 bc) was marked by the dissidence of Molon and his brother Alexander, satraps of Media and Persis, respectively. Antiochus did not undertake his campaign for recovery of the high satrapies—a project his father had planned and never carried out—until 212 bc. At that time his kingdom stretched no farther east than Media, Persis, Susiana, and Carmania. His operations against Artabanus were successful; he took Hecatompylos and crossed the mountains separating it from Parthia, which he occupied. Artabanus fled and took refuge with the friendly Apasiacae, as had his father, Arsaces. However, the conflict between the Seleucids and Parthia was ended by a compromise, just as it had been at the time of the invasion of Seleucus II. Because a much more important struggle, against the Bactrian kingdom of Euthydemus, awaited Antiochus, he preferred to make peace with Artabanus, to whom he accorded the title of king in exchange for recognition of his fealty, and he obliged the Parthian to send troops to reinforce the Syrian army. The rear of the Seleucid king was safeguarded, but the two provinces held by Artabanus were definitively lost by the Macedonians.
The period following Antiochus’s campaign against the Parthians was marked by a strong resistance by the Bactrian cavalry at the frontier and by a Seleucid siege of Bactra, for two years the Bactrian capital (208–207 bc). There, too, the Seleucid king made peace: Euthydemus, like Artabanus, kept his title of king. Demetrius, son of Euthydemus, married a daughter of Antiochus the Great, thus preserving his political prestige.
Having acquired war elephants and provisions for his army in Bactria, Antiochus crossed the Hindu Kush into the Kabul valley, where he concluded a pact with the Indian king Sophagasenos, secured still more elephants, and returned by way of southern Iran. The results of this long campaign were meagre. Antiochus recognized the independence of two kingdoms, that of the Parthians and that of Euthydemus, which previously had been no more than satrapies. The struggle must have weakened these two states, but, after their status was legalized, they proceeded to reestablish their material and military resources. Phraates I
Precise information is not available concerning the reign of Priapatius (c. 191–176 bc), who succeeded Artabanus and whose name appears in documents found in excavations at Nisā. Under his son Phraates I (reigned c. 176–171 bc), the young Parthian kingdom seems to have recuperated sufficiently to have taken up once again its expansionist activities. It attacked Media, succeeded in the conquest of the Mardi tribe near the Caspian Sea, and set up a defense of the “Caspian Gates,” an important strategic point of penetration in Phraates’ possessions. Overturning tribal tradition, which reserved the succession to the throne to the eldest son, he wisely designated as a successor—even though he had several sons—his brother Mithradates. The “phil-Hellenistic” period (c. 171 bc–ad 12)
The accession of Mithradates I about 171 bc opened a new period in the destinies of the Parthian kingdom, which historians call “phil-Hellenistic” and which lasted until ad 12. This period was characterized by a strong Hellenistic cultural influence, manifested in the use of the Greek language and in particular in the arts, where, however, national traditions were not completely abandoned. Mithradates I
Parthian military, political, and economic power expanded considerably following the accession of Mithradates I. The king began with an attack on the Greco-Bactrian kingdom, which at the time was going through a period of weakness; then he turned against the west and declared himself independent of the Seleucids. To show his complete independence—he was the first of the Parthian sovereigns to do so—he began issuing coins bearing his likeness wearing a royal diadem like the Seleucid kings. On the reverse side was a representation of Arsaces, ancestor of the Parthian dynasty, seated on an omphalos (hemispheric altar) and holding a bow, in imitation of Seleucid coins that showed Apollo in the same way, as the ancestor of the Seleucids.
The Seleucid king Antiochus IV Epiphanes took action against Mithradates but was killed at Tabae (or Gabae, probably present Eṣfahān). His death brought about a widespread dislocation of the Macedonian kingdom, which crumbled into several smaller states. Toward 160 bc the power to unite most of the high satrapies and other eastern satrapies could come only from the Parthians, who under Mithradates began the assault. They occupied Media in 155, which opened the route to Mesopotamia. In 148–147 Mithradates reached Ecbatana, where he moved his capital. Rhagae was “refounded” and given the dynastic name of Arsacia, and in 141 Mithradates took Seleucia on the Tigris and was recognized king of Babylonia. His forces conquered Susiana and Elymais, either at this time or after 139. In 141 he was obliged to leave Hyrcania for his eastern possessions, which were evidently being menaced by hostile movements of the nomads. There he spent the remaining three years of his reign.
The Seleucid king Demetrius II, probably aware of Mithradates’ difficulties in the east, undertook an effort to recover Mesopotamia, but after a few successes he suffered defeat and was taken prisoner (139 bc). He was sent to Hyrcania and was married there to a daughter of Mithradates, who by this union became related to the house of Seleucus. The army of Demetrius included Greco-Bactrian and Elymaian troops—which is understandable—as well as men from Persis, or Persians, who by their cooperation with the Macedonians seem to indicate their opposition to the expansionism of the Parthians, whom they considered foreigners and conquerors. Iran under the Parthians was an empire but not yet a nation. Phraates II
Like his father, Mithradates I, Phraates II (reigned c. 138–128 bc) was to remain for some time in the eastern provinces. He also endured a last Macedonian attempt to break the Parthian advance. Antiochus VII Sidetes—brother of Demetrius II, who had been taken prisoner—assembled a powerful army, which once more included men of Persis and Elymais. The strength in numbers and the wealth of this army made an impression on contemporaries, who reported that even the simple soldiers wore shoes cobbled with gold. Phraates was beaten in several battles, but time worked on his side. With the arrival of winter, Antiochus quartered his troops in several localities in Media. The local population, exasperated by the undisciplined Syrian soldiery, rose up in revolt. Antiochus was killed and his son taken prisoner (129 bc). Thanks to the loyalty of the Medians, whose sentiments contrasted with those of the Persians, Phraates was victorious. The year 129 bc was a turning point in the history of the eastern Mediterranean: Greco-Macedonian domination received a decisive blow; it would survive for only 46 more years.