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The Sasanian Empire

The Rise of the Sasanians

In the early third century CE the Parthian empire had entered a chronic period of civil war. It was also weakened in 217 by a Roman invasion deep into Mesopotamia. The Parthian ruling monarchy was weak, and power was slipping away from it, down to local rulers around the empire.

One such was Ardashir. He was a minor vassal of the king of Parthia, the grandson of a man called Sasan, after whom his dynasty was named. Ardashir’s fief was located in modern-day Fars (ancient Persia).

Identifying himself very closely with his Persian roots, and claiming to be the founder of a new Persian empire, Ardashir rose in open rebellion against the Parthian king in 212 CE and began to conquer neighboring local rulers. In 224 the Parthian king, Artabanus IV, having had to put down other rebellions in the empire, marched to deal with Ardashir. Ardashir defeated Artabanus’ army, killed the Parthian king, and assumed the ancient Iranian imperial title, “King of Kings”. He then went on to conquer the western provinces of the Parthian empire. He made his capital at Ctesiphon, which had been the capital of the Parthian empire. Within a few years he had won control of the entire empire, as well as parts of Armenia, northwest Arabia and the western portions of the Kushan empire.

Some changes

Internally, Ardashir continued the Parthian practice of entrusting the highest civil and military offices to the great noble families, but in other respects he was able to depart from former arrangements and concentrate more power into his own hands. He replaced most of the local dynasties of vassal kings with his own sons and relatives, who also took the title of king (shah). He centralized the administration of state revenue and developed an efficient bureaucracy, with more clearly defined ranks than before and thus presumably with more clearly defined lines of authority. Ardashir strengthening royal control over the army, and seems also to have carried through a tactical innovation by introducing the more flexible Roman-style chain mail into the army.

Ardashir thus gained an enduring reputation as an administrative reformer, and the efficiencies he introduced must have increased the effectiveness of the Sasanian army over its predecessor. Another change that his regime brought was the enhanced status of the Zoroastrian religion.

Zoroastrianism on the rise

So far as we can tell, under the Parthians Zoroastrianism had enjoyed neither special status nor special privileges. Adashir’s home region of Fars, however, seems to have been a principle center of the religion, and his own family had Zoroastrian priestly connections. Once king, Ardashir continued to practice the faith of his forefathers and as a result it significantly rose in status. He stopped short of instituting it as the state religion, however.

In his final years Ardashir turned his attention to the Roman Empire, which was now experiencing a period of great turbulence. He took some Roman border towns and besieged the important fortress of Hatra, which fell to his forces in 240. However, he died the following year, leaving his son Shapur to prosecute the war.

Success against the Romans

Shapur I (reigned 241–272 CE) was one of the most energetic and able of the Sasanian rulers. He won spectacular successes against the Roman Empire, and in the late 250s he ravaged the wealthy Roman province of Syria, capturing Antioch, one of the greatest cities of the Roman world. When his army returned home they brought with them thousands of skilled craftsmen and their families, whom he settled in cities throughout Iran.

A great victory

In 260 AD, Shapur inflicted the most humiliating defeat on the Romans that they ever experienced, when he took their emperor Valerian captive, along with 70,000 of his troops. These, like the deportees from Antioch, were settled throughout the Sasanian empire. For some years thereafter the defense of Rome’s eastern frontier was left in the hands of the ruler of Palmyra, a caravan city in Syria on the borders of the two empires.

Shapur expanded Sasanian territory on other fronts as well, so that by the end of his reign the empire stretched from the River Euphrates to the River Indus. It included Armenia, over which Shapur placed his son as king.

Internally, Shapur further strengthened the central government. He reformed the coinage and took a great interest in developing trade and industry within his empire. He carried out large scale public works such as dams and bridges to aid agriculture and commerce, in which he employed thousands of skilled craftsmen deported from Antioch and other Roman cities.

Developments in religion

Amongst these deportees from Roman territory were some Christians, who now found themselves free from the persecutions they had been experiencing within the Roman empire. Communities of Christians had been living in Mesopotamia and Iran (and indeed as far east as India) since the early days of the faith, but these newcomers may have provided a boost to Christianity’s fortunes out of proportion to their numbers. The religion certainly seems to have begun to spread more widely from this time on.

Shapur was notably tolerant in religious matters. During his reign, a prophet called Mani founded a new religion, Manichaeism, to which he even tried to convert Shapur. Mani claimed that his teachings combined and purified Zoroastrianism, Buddhism, and Christianity.

Shapur’s religious toleration did not survive him. Under his son, Bahram I (reigned 271–274), the Zoroastrian church became more organized and hierarchical, and consolidated its power at court – it now became, in fact, the official religion of the Sasanian state. This enabled it to begin persecuting other faiths. The Zoroastrian clergy were particularly enraged by Mani’s teachings, and Bahram had him tried and executed in 274.


In the succeeding reigns the Sasanian empire experienced political instability, as the issue which had so weakened the Parthian empire before it reappeared – the destabilizing power of the nobility. This class now pushed back against the forceful rule of the first two Sasanian monarchs. Rebellions, civil wars, the deposing and murder of reigning kings and royal princes were all features of the period. Unsurprisingly, the Sasanians experienced mixed fortunes in their wars with the Romans, who even managed to reach the gates of Ctesiphon on one occasion (283). Armenia slipped out of Sasanian control at this time.

Shapur II

The most bizarre episode may have occurred when the nobles elected an as-yet unborn baby as king (though there is no reliable evidence that this event actually took place). In any event, Shapur II came to the throne as an infant, and enjoyed one of the longest reigns of any monarch in world history (309-79).

Shapur II’s reign marked one of the high points in the history of the Sasanian empire. As a youth he demonstrated his effectiveness as a leader by acting vigorously against Arab raiders in Mesopotamia. He strengthened the empire’s desert border there with a line of fortifications.

Shapur spent much of his reign fighting against the Romans. These started when Constantine granted asylum to a refugee Sasanian prince. Also, having converted to Christianity himself, Constantine asserted protection over Christians in all lands, including the Persian empire.

Campaigns of varying significance were waged almost annually between 337 and 359, frequently to the advantage of the Persians. In 363, the emperor Julian marched as far as Ctesiphon, but a heavy Persian counterattack forced him to retreat, and he was killed in battle. His successor, Jovian (363-64) signed a “thirty-year peace treaty,” which obliged the Romans to return territory they had previously won, and surrender several border forts, some, such as Nisibis, of considerable importance. They also agreed to refrain from interfering in Armenia.

Limited local wars continued until Shapur’s death, but the frontier between the two empires remained stable for many years.

With Christianity the dominant religion in the Roman Empire, Persia’s great enemy, it is hardly surprising that that religion came to be seen as a threat by the Sasanian regime. Christians were viewed as a fifth column, and it was claimed that they refused to submit to the authority of the king of kings. Wars with Rome were normally accompanied by persecutions of Christians. These fears also strengthened the hand of the Zoroastrian clergy at court, and it was at this time that this faith was organized along the lines of a national church. The Zoroastrians developed an official hierarchy of priests modeled on that of the Christian Church.

External dangers did not come only from the west. On the northeastern frontier, a tribe related to the Huns now posed a growing threat to the Persians. Several times Shapur had to interrupt campaigns against the Romans and hurry east to deal with their raids.


After Shapur’s death, the Persian empire experienced another prolonged period of instability, with the Zoroastrian clergy and the nobility opposing the kings’ attempts to impose their will on the state, particularly if this meant toleration towards Christians and peaceful co-existence with Rome. All Shapur’s immediate successors were either deposed (383) or murdered (388, 399, 421). Bahram (reigned 421-39) was only allowed to ascend the throne on condition that he recognize the nobility’s privileges. Persecution of Christians resumed again during his reign, causing a short war with the Roman Empire (422). By the terms of the peace between the two empires both the Romans and the Persians agreed to tolerate each others’ religions within their realms.

By this time, developments within central Asia had led to the emergence of a powerful confederacy, ruled by a tribe called the White Huns, centered on Afghanistan. In the reign of Yazdegerd II (439-57) they inflicted a resounding defeat on Persian forces (454), and the Persians agreed to pay a heavy tribute to the Huns.

Yazdegerd’s death was followed by a round of civil wars, from which his elder son Peroz (reigned 459-84) emerged victorious. In 484 he attacked the White Huns, and he and his entire army were annihilated. The White Huns annexed a large area of the east of the empire, and imposed a heavy annual tribute on the empire. The nobility blamed Peroz for not consulting with them, and murdered his son Zarer. Instead they chose Peroz’ brother (and Zarer’s uncle), Balas, as king, first forcing him to agree to respect their privileges and consult with them in matters of policy.

Balas (reigned 484-8) pursued a peaceful foreign policy, and at home allowed Christians freedom of worship. By this time, in fact, the position of the Christian community within the Persian Empire had undergone a radical change with regard to the authorities. They had chosen to follow a branch of Christianity, the Nestorian, which was now being persecuted within the Roman Empire. This made them far less suspect to the Persian authorities. Indeed, when the Romans closed down the Nestorian school at Edessa in 471, it moved to Nisibis, within the Persian Empire’s borders, and continued to flourish with the support of the Persian authorities.


However, the payment of the heavy annual tribute to the White Huns, plus the various wars and a three year famine in Iran, sapped the strength of the Persian Empire. The troops became mutinous, and the nobility lost confidence in Balas. They deposed and blinded him and chose his nephew, Peroz’ son Kavadh (reigned 484-96, 496-531), to replace him.

At this moment, an extraordinary series of events began to unfold. A religious and social movement called the Mazdakites appeared, calling for the redistribution of land. Unsurprisingly this movement found widespread appeal amongst the poor, and bitter hostility amongst the nobility. As an indication of how poisoned relations between king and nobility had now become, Kavadh threw his weight behind the Mazdakites, seeing in it a means to cut down the power of the nobility.

Social anarchy engulfed some areas as groups of peasants dispossessed landowners by force. The nobility and clergy deposed and imprisoned Kavad and replacing him with his brother, Jamasp (reigned 496-8). However, Kavadh escaped to the White Huns. They sent him back at the head of a powerful army to regain his throne.


Kavadh now changed tack. Having seen the violence and misery caused by the Mazdakite movement, he massacred them. He also moved against the nobility. Many of these had lost their lives and their lands to the Mazdakites, and the class as a whole were in weakened state. Kavadh seized the opportunity to carry out a series of administrative reforms to centralize more power in his own hands. He revised the tax system so that it was administered by royal officials rather than being under the control of the nobles, and he reduced the power of the higher Zoroastrian clergy. He insisted on the right of the king to choose his heir, taking it out of the hands of the high nobility and clergy.

Kavadh also launched the first war against the Romans in sixty years, between 502 and 506, and again between 527 and 531. These swung one way, then the other; they achieved little, but are notable for the use of Arab allies along both empires’ southern borders.  Their chief result was to create Arab allied states, the Lakhmids for the Persians, and the Ghazzanids for the Romans.

Kavadh’s successor, Kosrow I (reigned 531-79), signed the “Endless Peace” with the Roman empire (or Byzantine Empire, as modern scholars call the late Roman empire of this period) which left the situation more or less as it had been before the wars. It lasted less than 10 years, and Kosrow fought several long wars with  the Byzantines (540-545, 549-557, 572 until his death – the war lasted until 591). These wars were expensive and destructive; several cities were sacked and their populations taken into captivity.

Internally, Kosrow consolidated the reforms of his father, Kavad. The administration was further centralized, and the army was retrained and re-equipped. A plot be some nobles to assassinate him was discovered and those involved killed.

Kosrow was determined to regain control of the eastern provinces of the empire from the White Huns. In alliance with Turkish tribes of central Asia he attacked them and destroyed their power. Unfortunately for the Persians, however, the Turks themselves were soon menacing their empire, and Kosrow was obliged to fortify the defenses along the north east frontier.

In the south, Kosrow conquered Yemen. This allowed him to control the sea routes between the Middle East and India.

Although Kosrow had been brought up as a Zoroastrian, he was broad-minded in his religious views. He granted freedom of religion to Jews and Christians; he studied Greek philosophy, and collected books of all the faiths and schools of thought that he knew about. He patronized scholarship and learning, arranging for the translation of works on science, medicine and astronomy from Greek and Indian originals into Persian. In this, Kosrow anticipated the Abbasid caliphs of Baghdad.


Immediately on Kosrow’s death the higher nobility and Zoroastrian clergy tried to regain the power they had lost in recent times. Kosrow’s successor, Hormozd IV (579-89), strenuously opposed them. Unfortunately for him, the seemingly endless wars with the Byzantines, serious raids by Arab tribes, invasions of Turkish nomads and internal rebellions sapped his prestige, and he was deposed and murdered by the nobility. His son Kosrow II, was appointed in his stead, but he was driven from his capital by rebels (590). He fled to Byzantine territory, and a Byzantine army helped him regain his throne.

The revolts were not fully suppressed for some 6 years, but with the re-establishment of peace, the Persian empire experienced a period of peace and stability. Kosrow (reigned 589-628) was able to build more splendid palaces and surround himself with a more brilliant court than any of his predecessors.

In about 600 Kosrow destroyed the power of the Arab dynasty of the Lakhmids, Persia’s long-standing allies. He thus removed an important barrier between the rich Persian province of Mesopotamia and the warlike Arabs of the Arabian desert. A generation later these would overrun Persian territory with remarkable ease.

The Great War

Kosrow is most famous for fighting one of the greatest wars in ancient history. In 602 he invaded the Byzantine Empire, with the clear aim of annexing as much territory as possible.  In the following years, Persian armies invaded and plundered Syria and Asia Minor. In 613 and 614, they besieged and captured Damascus and Jerusalem, and carried the most holy relic in Christendom, the “True Cross”, away in triumph. They conquered Egypt in 618. The Byzantines, beset by major invasions of Avars and Slavs from the Balkans, could put up little resistance, and the tide of Persian advance was barely interrupted by the need to deal with a major invasion of Turks and Huns in the east.

In 622, however, the Byzantine counter-attack at last began. The very capable emperor Heraclius collected a powerful force and, by-passing the traditional lines of Roman attack to the east, launched an invasion into northern Iran. Here he was joined by forces rebelling against Kosrow.

In 626  Persian army marched to Constantinople itself, and, with the help of Byzantium’s other enemies, the Avars and Slavs, laid siege to the city.  This besiegers failed to penetrate the great walls of Constantinople,  and Kosrow was forced to withdraw from Asia Minor (628).

Heraclius defeated the Persian army at Nineveh, in northern Mesopotamia, and then advanced on Ctesiphon, the Persian capital. However, rebel Persian forces captured Ctesiphon before he arrived, and Kosrow was imprisoned and then executed, along with other members of the royal family. His son, Kavadh II, then proclaimed himself king, with the backing of the nobility. He then made peace with the Byzantines.

The fall of the Persian empire

By the terms of this peace, the Byzantines regained all lost territory, as well as all the relics captured from Jerusalem in 614. The long war had left both empires exhausted, and the Persian Empire descending into anarchy. Kosrow II had been toppled by a group of leading nobles, but on his death they divided into various hostile factions. Civil wars followed, and kings – and two queens – came and went, few reigning more than a year.

Finally, in 632, a boy named Yazdegerd III ascended the throne. The next year, an Arab army invaded the empire carrying with it the new religion of Islam. They defeated a Persian army at Hira and occupied that city, but in 634 a Persian army defeated the Arabs at the Battle of the Bridge. In 636, at the Battle of Qadisiyya, a huge Persian army was heavily defeated, clearing the way for the Arabs to march on Ctesiphon and occupy Mesopotamia. Yazdegerd fled his capital for northern Iran, while another Persian army suffered a severe defeat, at Jalula (637). The Arabs began occupying Iran, against stiff resistance from local Persian lords, but at the battle of Nahavand (642) they inflicted a third great defeat on the Persians. Yazdegerd tried to organize resistance from a base in the north, but his demands for resources there rapidly lost him the support of the local population. Attempting to flee again, with just a few followers, he was killed by a local miller. By this time the rest of the Persian Empire had fallen to the Arabs.