Alexander the Great’s conquest of the vast Persian empire was followed, on his premature death in 321 BC, by struggles between his generals which, after some years, resulted in one of them, Seleucus acquiring most of Alexander’s Asiatic domains. He was able to found a huge kingdom, the rule over which he passed down to succeeding generations of his family, called the Seleucids.
The power of the Seleucids was always based in Syria and was concentrated in the western half of their extensive realm. Here they could focus their attention on their constant rivalries with the kings of Egypt, of Macedonia and of other states in the Hellenistic world.
The Seleucids’ eastern provinces received comparatively little of their attention. Unsurprisingly this led to a slackening of their hold on this region, until, in the 240s BC, the satraps of Parthia and Bactria made themselves independent of the Seleucid king. Exploiting this situation, Arsaces, the chief of an Iranian tribe called the Parni (originally from central Asia but recently settled along the Seleucid frontier), occupied Parthia. The line of kings which Arsaces founded was called the Arsacid dynasty, and the state they founded is often called the Arsacid empire.
Having established themselves on cultivated lands, the Parni began developing the most effective cavalry force yet seen. Some modern scholars think that they did this by turning over portions of their farmland to alfalfa, which provides an excellent fodder for horses. This enabled them to breed bigger and stronger horses which could carry the weight of armoured men on their backs, and even carry armour to protect their own bodies. The Parthians were thus able to develop the first heavy cavalry in history. Their armour gave them a much greater degree of protection than their foes, and their large, powerful horses allowed them to pursue retreating enemies faster and farther than before.
This new cavalry consumed much more fodder than previous mounted troops had done, and so had to be stationed in scattered strong points at some distance from each other across the land. These strongpoints soon formed the centres of political-military units in which nobles and their mounted warriors controlled and defended groups of farming villages, which in turn supported them in their warrior way of life. These fiefs constituted the local power-bases of a feudal aristocracy, which thus dominated the indigenous population.
This cavalry force seems to have been fully developed by 100 BC at the latest, and providing an effective defence against the steppe nomads.
Preoccupied with rivalries with other Hellenistic states in the Mediterranean region, the Seleucids were unable to organize a campaign in the east until the end of the 230s. Even then, rebellions in Asia Minor soon forced the king Seleucus II to return west with little achieved. It would be two decades before the next Seleucid effort to regain these eastern regions, under Antiochus the Great. This led to a treaty by which the Parthians and Greco-Bactrians nominally recognized the Seleucids as their overlords, but in reality retained their independence.
The Seleucid kings soon slacked their grip on the east again. The Parthians, under their king, Mithridates I (reigned c. 164-132 BC), conquered the neighbouring kingdom of Media in c. 148 BC. Soon after this they brought the eastern Seleucid capital of Seleucia, in southern Mesopotamia, under their control. Mithridates had himself crowned there.
In Phraates II’s reign (139-128 BC) the Seleucids made a final attempt to regain their eastern provinces, but this met with disaster when the Seleucid king, Antiochus VII, was killed (129 BC).
The Parthians were unable to rest of their laurels. A nomadic people from the steppes of central Asia, the Scythians, had come to dominate the central Asian steppes north of Iran, and then conquered the kingdom of Bactria (c. 150 BC) and then founded large empires in Afghanistan and the Indian sub-continent. They posed a grave threat to Parthian power in eastern Iran. Both Phraates II and his successor Artabanus I (127-23 BC) lost their lives whilst fighting against them, but gradually they were pushed back.
Mithridates II (reigned 123-87 BC) was a vigorous ruler who reduced several kingdoms in Mesopotamia - Characene, Adiabene, Gordyene, and Osrhoene - to vassal status. Then he deposed the king of Armenia, replacing him with his own son, Tigranes. He also annexed some Armenian territory. Mithridates assumed the traditional Iranian imperial title “King of Kings”, and established a new capital for his empire, Ctesiphon. This was a short distance away from the old Seleucid capital of Seleucia, which itself was very near the ancient city of Babylon.
Around 115 BC the Parthian court was visited by ambassadors from the Chinese emperor Wudi, and the two states reached an agreement on opening up the trade route across central Asia which would later become famous as the Silk Road. This would significantly boost long-distance trade within the empire and enrich the treasury of the Parthian kings.
The Parthians’ conquests had taken their kings from ruling a comparatively small-scale, feudal society on the margins of civilization, to governing a large, multinational empire of world significance. This dramatic expansion exacerbated tensions between kings and nobles. These had already been present before the conquests began and would never really be properly resolved, weakening the Parthian empire throughout its existence.
It was not so long before that the Parthians had been a semi-nomadic people on the steppes of central Asia. In such groups the authority of kings and chiefs was respected - so long as they retained the support of their nobles. In the tough conditions of the steppes this meant providing effective leadership in war. In the very different circumstances of running a large state, keeping this support was not so straightforward.
The kings followed the Iranian practice of giving leading nobles high office in government and army. As well as serving the kings as top ministers and generals, these aristocrats naturally maintained close links, by marriage and friendship, with the nobility at large. This class was keenly jealous of its ancestral privileges and deeply suspicious of the new powers an imperial monarchy might potentially acquire; the nobles feared that they could lose their rightful (as they saw it) influence in affairs of state.
This latent tension was fuelled by another factor. The Parthians now ruled numerous Hellenistic cities, thriving centres of Greek civilization. These had originally been planted by Alexander the Great and his Seleucid successors, and were scattered throughout Iran and in particular Mesopotamia. To win the support of these cities (and perhaps to lessen their own dependency on their troublesome nobility), the Parthian kings allowed them to continue to exercise the autonomy which they had enjoyed under the Seleucids.
The Hellenistic cities prospered under their new Parthian rulers. More than any other element within Parthian society they benefited from the opening of the Silk Road, and from the expansion of maritime trade across the Indian Ocean during Parthian times.
The Parthian kings presented themselves as philhellenes, champions of Greek civilization; nor was this mere propaganda - the Parthian kings became Hellenistic in their ways, patronizing Greek art, architecture and literature and having Greek plays put on at their court.
This situation had a baneful influence on the high politics of the empire. The sophisticated, urban, philhellenism of the Parthian kings was deeply unpopular with the nobility, which had, with the conquests, become the leading element within the broader Iranian aristocracy. This already nursed a sense of grievance from being excluded from the levers of power during more than a century of Seleucid rule, under which foreigners - Macedonians and Greeks - had a lock on power. The aristocracy's inate conservative tendencies were thus amplified by strong anti-Hellenistic sentiments.
Moreover, the nobility had chaffed under the masterful style of rule of both Mithridates I and Mithrditates II, and towards the end of the latter’s reign disorders seem to have broken out. A series of power struggles resulted in a succession of obscure kings sitting briefly on the Parthian throne. The empire was thus weakened to the extent that the Armenians were able to retake territory lost to Mithridates II.
Clashes with Rome
In 53 BC, Orodes II (reigned 57-37 BC) was able to dispose of his rivals and restore some stability. Just in time: Orodes was hardly on the throne when Parthia found itself involved in the first of a long series of struggles with a great new power in the Middle East, the Roman empire. A Roman commander, Crassus, led a huge army into Parthia, only to meet defeat and death at the battle of Carrhae (53 BC). Orodes had his skull encrusted with jewels and used it as a wine cup.
The Parthian general responsible for this brilliant success, Surena, was murdered soon after this on the orders of Orodes, who saw him as a potential threat to his position.
A wasted opportunity
In the event, this great Parthian victory changed very little. Orodes failed to follow up with an attack on Roman territory until ten years later, and when he did launch a major attack in 41 BC, the Parthians were defeated.
After Orodes there followed another long bout of political instability. The Romans naturally exploited this situation by invading Armenia (20 BC), at that time ruled by the pro-Parthian king Artaxes. This led the Parthians to agree to Roman demands for the return of the captives and legionary standards which had been captured at Carrhae, and to accept Roman overlordship over Armenia. In exchange, Rome recognized the Euphrates as the frontier with the Parthians.
This treaty ushered in many years of peace between the two empires. During this time, members of the Parthian royal family regularly went to live in Rome for periods of time, becoming even more Hellenised in outlook and culture than before. This alienated the Iranian nobles still more; for them the Romans were almost indistinguishable from the Hellenistic conquerors who had occupied their country for so long.
Political instability and its effects
The nobles became increasingly nationalistic in their outlook, and increasingly wished to suppress alien influences. Instability continued as the nobility repeatedly challenged royal power, and they were able to get rid of kings they did not like and replace them with more amenable princes of the royal family. The last of the philhellenic kings, Vonones I, was ousted from the throne in AD 12, and in his place they chose Artabanus III (reigned 12-38), well known for his anti-Hellenistic, pro-Iranian sympathies (he had produced a genealogy of the Parthian royal family purporting to show its descent from the great Achaemenid kings). From then on Hellenistic cultural influences began to decline, whilst native Iranian elements grew stronger.
Despite coming to the throne with the support of the nobles, Artabanus’ reign was a turbulent one (he was deposed - and reinstated - three times). The end of his reign found the nobles effectively in charge, and under Artabanus' successors different aristocratic factions struggled for power. Coups, assassinations and civil wars became a regular feature of Parthian politics. The authority of the kings weakened, and the Parthian empire gradually ceased to function as a unified state. It effectively became divided into several kingdoms, each under native monarchs who owed only loose allegiance to the Parthian king. The only circumstances in which any concerted action could take place was to repel an invasion. It is hardly surprising that, in these circumstances, the Parthian kingd should be unable to prevent the break-away of their eastern possessions under an Indo-Parthian king called Gondophares.
Political instability also sapped Parthia’s ability to consistently oppose Roman ambitions in Armenia. Despite regular bouts of warfare between the two empires, this country generally remained within the Roman sphere of influence. In one spectacular episode, the King of Parthia, Osroes, having installed his own nominee as king of Armenia in 114 AD, the Romans, under their ambitious emperor, Trajan, reacted by marching into Armenia, then on into Mesopotamia and Iran, occupying the Parthian capital, Ctesiphon, itself. They then travelled onwards, reaching as far as the Persian Gulf.
Risings against Roman rule began almost at once, led by members of the Iranian nobility. The Romans soon found themselves getting bogged down, throwing more and more resources at holding the territory they had so easily won. On Trajan’s death (117 AD), therefore, his successor Hadrian pulled the Roman forces back to their frontier.
Ironically, the main casualties of this episode had been the numerous cities of Mesopotamia, the scene of most of the fighting. These were the main seats of Hellenistic culture within the Parthian empire, and the upshot was a further weakening of Hellenism in the region.
The latent hostility between kings and nobles, and the instability that this produced, continued to plague the Parthian empire for the rest of the 2nd century AD, and on into the 3rd. Civil wars were a frequent occurrence, and the struggle with Rome for control of Armenia also flared up at regular intervals. Twice again, in 166 and 195 AD, the Romans were able to advance to the Parthian capital; neither time could they hold it. In the second episode, however, under the emperor Septimius Severus, the Romans were able to permanently push their frontier eastward at Parthian expense.
In the 3rd century the Roman empire was entering a less stable period in its history, and this gave the Parthians a slight reprieve. Another Roman invasion in 217 ended in a Parthian victory and the Romans having to pay a large indemnity.
Shortly after this success the Parthian regime itself fell from power. By the beginning of the 3rd century, the Parthian empire was weak and divided. Underneath the veneer of a single empire lay a multitude of small kingdoms. The ruler of one of these states, Persis (modern Fars), was called Ardashir. In 215 he rebelled against the Parthian king and began to bring neighbouring territories under his control. The Parthian king, Artabanus IV, was as usual having to deal with rebellions elsewhere, and it was not until 224 that he was able to march against Ardashir. Ardashir decisively defeated him. The Parthian King was killed, and power swiftly passed to Ardashir.
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