Persian Empire
Deep Dive 9 min read

Founding and Rise of the Parthian Empire

The date 247 BCE, on which the Arsacid dynasty’s later regnal count began, is a Roman-era fiction. Justin’s Epitome of the Philippic History of Pompeius Trogus preserves it, and Justin was working two centuries after the event from a source (Trogus) that was working from still earlier and partly derivative material. The Parni who became “Parthians” probably began to assert themselves in the late 260s or 250s BCE; whether the figure called Arsaces I actually led the revolt, or whether he inherited a movement that was already in motion, is genuinely undecidable. A. D. H. Bivar’s chapter in the Cambridge History of Iran (1983, pp. 21–35) and Josef Wiesehöfer’s Ancient Persia (1996, pp. 116–122) both treat the problem with the caution it deserves. To my mind, the most useful thing the founding legend tells us is that the dynasty itself wanted to be counted from a single regnal year — a fact that says something about Arsacid self-image in the second century BCE, when the count was standardised, rather than about the events of 247.

This article works through what we can say about the founding and rise of the Parthian state, and what we cannot.

The Parni, the Parthava, and a confusion that has stuck

The confusion between Parthia and Parni is older than the dynasty. Herodotus already knew both names. Parthava is the Old Persian form of the name of the Achaemenid satrapy in the northeast of the Iranian plateau, south-east of the Caspian, the region the Greeks called Parthyene. The Behistun inscription (c. 520 BCE) lists Parthava among the rebellious provinces that Darius defeated in his accession-year campaign — DB §20 — and the territory remained a unit of Achaemenid administration down to the empire’s end. The Parni, by contrast, were a different group, pastoralists of the steppe east of the Caspian, neighbours of the Dahae and the Sacae, and clients of the Seleucid crown. The two populations became one in the third century BCE when the Parni invaded or migrated into the older Parthian territory, absorbed the local Iranian-speaking population, and took the name.

This matters because the dynasty’s later claim of Achaemenid descent — the genealogy that Movses Khorenats’i transmits in his History of Armenia and that Firdowsi adopts in the Shahnameh — almost certainly has its origin in the conflation. A Sasanian-Armenian-Sogdian tradition of the early common era worked the two names into a single lineage: the Arsacids as the legitimate heirs of Cyrus and Darius, and the Sasanians (from a different family) as the rightful usurpers of an Arsacid inheritance. Whether the Arsacids themselves ever made the claim is hard to say. The earliest surviving Arsacid coinage — from Arsaces II onward — uses the title king (βΑΣΙΛΕΩΣ) without genealogical ornament, and the famous “lover of Greeks” epithet (ΦΙΛΕΛΛΗΝΟΣ) is the cultural language of Hellenistic monarchy, not Achaemenid restoration. I am not aware of any external evidence that predates the second century BCE for an Arsacid Achaemenid genealogy, and I suspect the claim is a legitimation that hardened in the Sasanian period, when it suited the new dynasty to grant their predecessors some retrospective dignity.

The Seleucid collapse and the Arsacid opening

The Seleucid empire of the third century was a kingdom in slow disintegration. The loss of Coele-Syria to the Ptolemies, the succession wars of the Seleucid house, and the chronic revolt of the upper satrapies left Parthia, Hyrcania, Aria, and Bactria effectively autonomous by the 250s. Andragoras, the Seleucid satrap of Parthia, had himself struck coins in the name of independence shortly before the Parni takeover; the political space the Parni occupied was already open.

Antiochus III (r. 223–187 BCE), the most energetic of the later Seleucids, made a serious attempt to recover the east in his anabasis of 212–205 BCE. He retook Bactria, Aria, and parts of Parthia, and reduced the Arsacid king to tributary status. Justin says the Arsacid of the moment was a boy, with the real power in the hands of a regent — a detail that is impossible to verify but consistent with the general picture. The settlement collapsed within a few years of Antiochus’ withdrawal to the west. His catastrophic defeat at Magnesia in 190 BCE against the Romans, and the subsequent Treaty of Apamea (188 BCE), stripped the Seleucid crown of its Anatolian revenues and ended its capacity to project force into the upper satrapies. After Magnesia, the Arsacid state settled into a lengthening lease on the Iranian plateau. The moment of 247 is a fiction, but the moment of 188 is the real one.

Mithridates I, and the moment the state became an empire

Mithridates I (r. c. 171–138 BCE) is the figure who turned a north-eastern Iranian kingdom into something like an empire. The chronology is partly conjectural, and Bivar’s reconstruction, with Wiesehöfer’s revisions, is the working reference. The decisive moves were three. In 148 BCE Mithridates took Media — the heartland of the Iranian plateau and the source of much of its military manpower. In 141 BCE he captured Seleucia-on-the-Tigris, the great Hellenistic city that would become the Parthian winter capital. In 139 BCE the Seleucid king Demetrius II was taken prisoner in a cavalry engagement; he was sent back to Syria only after years of captivity and a marriage alliance.

Seleucid Mesopotamia fell to Mithridates within a generation. The Arsacid kings ruled as shahanshah — king of kings — and Mithridates was the first to use the title on the coinage. The drachm of Mithridates I, with the legend ΒΑΣΙΛΕΩΣ ΒΑΣΙΛΕΩΝ ΑΡΣΑΚΟΥ ΕΥΕΡΓΕΤΟΥ ΕΠΙΦΑΝΟΥΣ ΦΙΛΕΛΛΗΝΟΣ (“of the King of Kings Arsaces, the Benefactor, the Manifest, the Lover of Greeks”), set the standard Parthian silver type. The fineness of the drachm — about 70% silver under Mithridates I — declined over the next two and a half centuries to as low as 30% in the second century CE. The decline is the most quantitative single indicator of the Sasanian-vs-Arsacid comparison that the coinage allows.

Mithridates II, the silk road, and the structure of the Arsacid state

Mithridates II “the Great” (r. c. 124–88 BCE) is the first Parthian king about whom something like a connected political history is recoverable. The Chinese envoy Zhang Qian’s report in the Shi-ji of Sima Qian places a Parthian embassy, and the famous gift of crossbow bolts and iron, in the reign of Wu Di, conventionally 115 BCE. The Roman treaty, sometimes called the Treaty of Sulla, is dated to 96 or 92 BCE; the text is lost, but Justin, Plutarch, and the periochae of Livy allude to a treaty that fixed the Euphrates as the boundary and arranged for extradition. The treaty is the first formal recognition of Parthia as a peer of Rome.

The internal structure of the Arsacid state under Mithridates II is partly reconstructable. The king of kings ruled with the consent and active support of the great noble families, of which the Suren, the Karen, the Aspahapet, and the Ispahbudhan are the best attested. The Suren were hereditary generals and held the right of crowning the king of kings — a privilege that, in the second century CE, became an instrument of regicide. The dynasty was technically elective within the Arsacid house in the early period, and a strong noble faction could and frequently did depose and replace a king. A king’s authority was as much a function of his personal following, his army, and his marriage alliances as of his lineage. Parvaneh Pourshariati’s Decline and Fall of the Sasanian Empire (2008) argues, in my view persuasively, that this noble-led, federative structure was the dominant feature of late Arsacid politics and persisted into the Sasanian period — a thesis that has not gone unchallenged (see Daryaee in Oxford Handbook of Iranian History, 2012, for a more state-centred reading) but has shifted the consensus.

Ctesiphon, and the bilingual court

Mithridates I founded a capital on the Tigris, near the older Greek city of Seleucia, and named it Ctesiphon — the site is on the east bank, about thirty-five kilometres south of modern Baghdad. Ctesiphon grew rapidly; by the first century BCE it was one of the great cities of the Near East, and the Parthian chancery, mints, and court were based there. The old Seleucid foundation of Seleucia remained a largely Greek-speaking city in the early Parthian period — Strabo describes a Greek politeia with a popular assembly and a senate — and there was substantial civic friction between the Greek population of Seleucia and the new royal foundation across the river. Vologases I eventually sacked Seleucia in the first century CE and rebuilt Ctesiphon on a larger scale.

The Parthian state was bilingual at the elite level. The kings used Greek for their coin legends, the official seals, and the chancery documents that have survived at the site of Old Nisa (modern Bagir in Turkmenistan). Middle Parthian, the language of the western Iranian highlands, was the spoken language of the dynasty and the great nobles; the surviving documents from Nisa are in Parthian. The cultural synthesis was real. Greek artistic conventions, particularly the Hellenistic ruler-portrait, were adopted into Parthian royal iconography and persisted into Sasanian times; the Sasanian rock reliefs at Naqsh-e Rostam and Bishapur still show clear traces of this tradition. But the institutional weight was Iranian, and the great families, the Zoroastrian priesthood, and the agricultural populations of the Iranian plateau gave the state its essential character. Ctesiphon, in time, would become the Sasanian capital, and the great Sasanian palace — the taq-i kisra, with its 30-metre vault — still stands in modern Salman Pak.

A note on the evidence

A word of caution. There is no Persian-language narrative history of the Parthian period. The Greek and Roman sources are abundant but interested; the Armenian and Syriac sources are fragmentary; the Chinese sources are at one or two removes; the archaeological record — the documents from Nisa, the coinage, the occasional inscription — fills in some gaps but is unevenly distributed. Reconstructing the dynasty’s internal history requires patience, and the reconstructions are improving as the French-Turkmen excavations at Old Nisa (underneath the leadership first of G. A. Koshelenko and then of various successors) and the Italian-Turkish work at Merv continue to publish. What can be said with some confidence: the Arsacid state was, from the early second century BCE onward, a coherent and adaptive system that was the chief rival of Rome for control of the Near East, and the dynasty that the Sasanians overthrew in 224 CE had ruled, with interruptions, for nearly five centuries.

For further reading

  • Bivar, A. D. H. “The Political History of Iran under the Arsacids,” in The Cambridge History of Iran, vol. III (1983). Still the most thorough treatment in English, with the chronological problems honestly faced.
  • Wiesehöfer, Josef. Ancient Persia (1996). A reliable single-volume synthesis, broader in scope than Bivar.
  • Pourshariati, Parvaneh. Decline and Fall of the Sasanian Empire (2008). The revisionist account of the late Arsacid noble-led structure.
  • Curtis, Vesta Sarkhosh, ed. The Parthian Empire and its Successors (2012). The most useful collection of recent scholarship in English.
  • Sellwood, David. “Parthian Coins,” in The Cambridge History of Iran, vol. III (1983). The numismatic backbone of any Parthian chronology.
  • Koshelenko, G. A. The First Parthian State (in Russian; 2004). The Soviet/Russian tradition on Old Nisa, with details the English-language literature tends to miss.