Sasanian Empire

Conflicting accounts shroud the details of the fall of the Parthian Empire and subsequent rise of the Sassanian Empire in mystery. The Sassanian Empire was established in Estakhr by Ardashir I.

Ardashir's father, Papak, was originally the ruler of a region called Khir. However, by 200, Papak had managed to overthrow Gochihr and appoint himself the new ruler of the Bazrangids. Papak's mother, Rodhagh, was the daughter of the provincial governor of Pars. Papak and his eldest son Shapur managed to expand their power over all of Pars. Subsequent events are unclear due to the elusive nature of the sources. It is certain, however, that following the death of Papak, Ardashir, the governor of Darabgerd, became involved in a power struggle with his elder brother Shapur. Sources reveal that Shapur, leaving for a meeting with his brother, was killed when the roof of a building collapsed on him. By 208, over the protests of his other brothers, who were put to death, Ardashir declared himself ruler of Pars.

Once Ardashir was appointed shah (King), he moved his capital further to the south of Pars and founded Ardashir-Khwarrah. The city, well protected by high mountains and easily defensible due to the narrow passes that approached it, became the center of Ardashir's efforts to gain more power. After establishing his rule over Pars, Ardashir rapidly extended his territory, demanding fealty from the local princes of Fars, and gaining control over the neighbouring provinces of Kerman, Isfahan, Susiana and Mesene. This expansion quickly came to the attention of Artabanus V, the Parthian king, who initially ordered the governor of Khuzestan to wage war against Ardashir in 224, but Ardashir was victorious in the ensuing battles.

Around 208 Vologases VI succeeded his father Vologases V as king of the Arsacid Empire. He ruled as the uncontested king from 208 to 213, but afterwards fell into a dynastic struggle with his brother Artabanus IV, who by 216 was in control of most of the empire, even being acknowledged as the supreme ruler by the Roman Empire. The Sasanian family had meanwhile quickly risen to prominence in their native Pars, and had now under prince Ardashir I begun to conquer the neighboring regions and more far territories, such as Kirman. At first, Ardashir I's activities did not alarm Artabanus IV, until later, when the Arsacid king finally chose to confront him.

The Battle of Hormozdgan was the climactic battle between the Arsacid and the Sasanian dynasties that took place on April 28, 224. The Sasanian victory broke the power of the Parthian dynasty, effectively ending almost five centuries of Parthian rule in Iran, and marking the official start of the Sasanian era.

Ardashir I assumed the title of shahanshah ("King of Kings") and started the conquest of an area which would be called Iranshahr (Ērānshahr). Vologases VI was driven out of Mesopotamia by Ardashir I's forces soon after 228. The leading Parthian noble-families (known as the Seven Great Houses of Iran) continued to hold power in Iran, now with the Sasanians as their new overlords. The early Sasanian army (spah) was identical to the Parthian one. Indeed, the majority of the Sasanian cavalry composed of the very Parthian nobles that had once served the Arsacids. This demonstrates that the Sasanians built up their empire thanks to the support of other Parthian houses, and has due to this has been called "the empire of the Persians and Parthians".

As late as the Parthian period, a form of Zoroastrianism was without a doubt the dominant religion in the Armenian lands. The Sassanids aggressively promoted the Zurvanite form of Zoroastrianism, often building fire temples in captured territories to promote the religion. During the period of their centuries-long suzerainty over the Caucasus, the Sassanids made attempts to promote Zoroastrianism there with considerable successes, and it was prominent in the pre-Christian Caucasus (especially modern-day Azerbaijan).

Shapur I was the second Sasanian King of Kings of Iran. During his co-regency, he helped his father with the conquest and destruction of the Arab city of Hatra, whose fall was facilitated, according to Islamic tradition, by the actions of his future wife al-Nadirah. Shapur also consolidated and expanded the empire of Ardashir I, waged war against the Roman Empire , and seized its cities of Nisibis and Carrhae while he was advancing as far as Roman Syria. Although he was defeated at the Battle of Resaena in 243 by Roman emperor Gordian III (r. 238–244), he was the following year able to win the Battle of Misiche and force the new Roman Emperor Philip the Arab (r. 244–249) to sign a favorable peace treaty that was regarded by the Romans as "a most shameful treaty".

Shapur later took advantage of the political turmoil within the Roman Empire by undertaking a second expedition against it in 252/3–256, sacking the cities of Antioch and Dura-Europos. In 260, during his third campaign, he defeated and captured the Roman emperor, Valerian.

Shapur had intensive development plans. He ordered the construction of the first dam bridge in Iran and founded many cities, some settled in part by emigrants from the Roman territories, including Christians who could exercise their faith freely under Sassanid rule. Two cities, Bishapur and Nishapur, are named after him. He particularly favoured Manichaeism, protecting Mani (who dedicated one of his books, the Shabuhragan, to him) and sent many Manichaean missionaries abroad. He also befriended a Babylonian rabbi called Samuel.

The Eastern provinces of the fledgling Sasanian Empire bordered on the land of the Kushans and the land of the Sakas (roughly today's Turkmenistan, Afghanistan and Pakistan). The military operations of Shapur's father Ardashir I had led to the local Kushan and Saka kings offering tribute, and satisfied by this show of submission, Ardashir seems to have refrained from occupying their territories.

Soon after the death of his father in 241 CE, Shapur felt the need to cut short the campaign they had started in Roman Syria, and reassert Sasanian authority in the East, perhaps because the Kushan and Saka kings were lax in abiding to their tributary status. However, he first had to fight "The Medes of the Mountains" - as we will see possibly in the mountain range of Gilan on the Caspian coast - and after subjugating them, he appointed his son Bahram (the later Bahram I) as their king. He then marched to the East and annexed most of the land of the Kushans, and appointing his son Narseh as Sakanshah - king of the Sakas - in Sistan. In 242 CE, Shapur conquered Khwarezm.

Ardashir I had, towards the end of his reign, renewed the war against the Roman Empire, and Shapur I had conquered the Mesopotamian fortresses Nisibis and Carrhae and had advanced into Syria. In 242, the Romans under the father-in-law of their child-emperor Gordian III set out against the Sasanians with "a huge army and great quantity of gold," (according to a Sasanian rock relief) and wintered in Antioch, while Shapur was occupied with subduing Gilan, Khorasan, and Sistan.

The Romans later invaded eastern Mesopotamia but faced tough resistance from Shapur I who returned from the East. The young emperor Gordian III went to the Battle of Misiche and was either killed in the battle or murdered by the Romans after the defeat. The Romans then chose Philip the Arab as Emperor. Philip was not willing to repeat the mistakes of previous claimants, and was aware that he had to return to Rome to secure his position with the Senate. Philip concluded a peace with Shapur I in 244; he had agreed that Armenia lay within Persia's sphere of influence. He also had to pay an enormous indemnity to the Persians of 500,000 gold denarii.

Shapur I then reconquered Armenia, and incited Anak the Parthian to murder the king of Armenia, Khosrov II. Anak did as Shapur asked, and had Khosrov murdered in 258; yet Anak himself was shortly thereafter murdered by Armenian nobles. Shapur then appointed his son Hormizd I as the "Great King of Armenia". With Armenia subjugated, Georgia submitted to the Sasanian Empire and fell under the supervision of a Sasanian official. With Georgia and Armenia under control, the Sasanians' borders on the north were thus secured.

Shapur I used Roman incursions into Armenia as pretext and resumed hostilities with the Romans. The Sassanids attacked a Roman force of 60,000 strong at Barbalissos and the Roman army was destroyed. The defeat of this large Roman force left the Roman east open to attack and led to the eventual capture of Antioch and Dura Europos three years later.

During Shapur's invasion of Syria he captured important Roman cities like Antioch. The Emperor Valerian (253–260) marched against him and by 257 Valerian had recovered Antioch and returned the province of Syria to Roman control. The speedy retreat of Shapur's troops caused Valerian to pursue the Persians to Edessa. Valerian met the main Persian army, under the command of Shapur I, between Carrhae and Edessa, with units from almost every part of the Roman Empire, together with Germanic allies, and was thoroughly defeated and captured with his entire army.

In 295 or 296, Narseh declared war on Rome. He appears to have first invaded western Armenia, retaking the lands delivered to King Tiridates III of Armenia in the peace of 287. Narseh then moved south into Roman Mesopotamia, where he inflicted a severe defeat on Galerius, then commander of the Eastern forces, in the region between Carrhae (Harran, Turkey) and Callinicum (Raqqa, Syria).

However in 298, Galerius defeated the Persians in the Battle of Satala in 298, sacking the capital Ctesiphon, capturing the treasury and the royal harem.

The battle was followed by the Treaty of Nisibis, highly advantageous to Rome. It ended the Roman–Sasanian war; Tiridates was restored to his throne in Armenia as a Roman vassal, and the Georgian Kingdom of Iberia was acknowledged as also falling under Roman authority. Rome itself received a part of Upper Mesopotamia that extended even beyond the Tigris - including the cities of Tigranokert, Saird, Martyropolis, Balalesa, Moxos, Daudia, and Arzan.

Shapur II was the tenth Sasanian King of Kings of Iran. The longest-reigning monarch in Iranian history, he reigned for the entirety of his 70-year life, from 309 to 379.

His reign saw the military resurgence of the country, and the expansion of its territory, which marked the start of the first Sasanian golden era. He is thus along with Shapur I, Kavad I and Khosrow I, regarded as one of the most illustrious Sasanian kings. His three direct successors, on the other hand, were less successful. At the age of 16, he launched enormously successful military campaigns against Arab insurrections and tribes who knew him as 'Dhū'l-Aktāf ("he who pierces shoulders").

Shapur II pursued a harsh religious policy. Under his reign, the collection of the Avesta, the sacred texts of Zoroastrianism, was completed, heresy and apostasy were punished, and Christians were persecuted. The latter was a reaction against the Christianization of the Roman Empire by Constantine the Great. Shapur II, like Shapur I, was amicable towards Jews, who lived in relative freedom and gained many advantages in his period. At the time of Shapur's death, the Sasanian Empire was stronger than ever, with its enemies to the east pacified and Armenia under Sasanian control.

In 337, just before the death of Constantine the Great, Shapur II, provoked by the Roman rulers' backing of Roman Armenia, broke the peace concluded in 297 between emperors Narseh and Diocletian, which had been observed for forty years. This was the beginning of two long drawn-out wars (337–350 and 358-363) which were inadequately recorded.

After crushing a rebellion in the south, Shapur II invaded Roman Mesopotamia and captured Armenia. Apparently, nine major battles were fought. The most renowned was the inconclusive Battle of Singara (modern Sinjar, Iraq) in which Constantius II was at first successful, capturing the Persian camp, only to be driven out by a surprise night attack after Shapur had rallied his troops. The most notable feature of this war was the consistently successful defence of the Roman fortress city of Nisibis in Mesopotamia. Shapur besieged the city thrice (in 338, 346, 350 CE), and was repulsed each time.

Although victorious in battle, Shapur II could make no further progress with Nisibis un-taken. At the same time he was attacked in the east by Scythian Massagetae and other Central Asia nomads. He had to break off the war with the Romans and arrange a hasty truce in order to pay attention to the east. Roughly around this time the Hunnic tribes, most likely the Kidarites, whose king was Grumbates, make an appearance as an encroaching threat upon Sasanian territory as well as a menace to the Gupta Empire. After a prolonged struggle (353–358) they were forced to conclude a peace, and Grumbates agreed to enlist his light cavalrymen into the Persian army and accompany Shapur II in renewed war against the Romans, particularly participating in the Siege of Amida in 359.

In 358 Shapur II was ready for his second series of wars against Rome, which met with much more success. In 359, Shapur II invaded southern Armenia, but was held up by the valiant Roman defence of the fortress of Amida, which finally surrendered in 359 after a seventy-three-day siege in which the Persian army suffered great losses. 

In 363 the Emperor Julian, at the head of a strong army, advanced to Shapur's capital city of Ctesiphon and defeated a presumably larger Sassanian force at the Battle of Ctesiphon; however, he was unable to take the fortified city, or engage with the main Persian army under Shapur II that was approaching. Julian was killed by the enemy in a skirmish during his retreat back to Roman territory. His successor Jovian made an ignominious peace in which the districts beyond the Tigris which had been acquired in 298 were given to the Persians along with Nisibis and Singara, and the Romans promised to interfere no more in Armenia.

According to the peace treaty between Shapur and Jovian, Georgia and Armenia were to be ceded to Sasanian control, and the Romans forbidden from further involvement in the affairs of Armenia. Under this agreement Shapur assumed control over Armenia and took its King Arsaces II (Arshak II), the faithful ally of the Romans, as prisoner, and held him in the Castle of Oblivion (Fortress of Andməš in Armenian or Castle of Anyuš in Ḵuzestān).

Confrontations with nomadic tribes from Central Asia soon started to occur. Ammianus Marcellinus reports that in 356 CE, Shapur II was taking his winter quarters on his eastern borders, "repelling the hostilities of the bordering tribes" of the Chionites and the Euseni (Kushans), finally making a treaty of alliance with the Chionites and the Gelani in 358 CE.

From around 360 CE however, during his reign, the Sasanids lost the control of Bactria to invaders from the north, first the Kidarites, then the Hephthalites and the Alchon Huns, who would follow up with the invasion of India.

Sasanian Armenia refer to the periods in which Armenia was under the suzerainty of the Sasanian Empire or specifically to the parts of Armenia under its control such as after the partition of 387 when parts of western Armenia were incorporated into the Roman Empire while the rest of Armenia came under Sasanian suzerainty but maintained its existing kingdom until 428.

In 428 marked the start of a new era known as the Marzpanate period, a period when marzbans, nominated by the Sasanian emperor, governed eastern Armenia, as opposed to the western Byzantine Armenia which was ruled by several princes, and later governors, under Byzantine suzerainty. The Marzpanate period ended with the Arab conquest of Armenia in the 7th century, when the Principality of Armenia was established. An estimated three million Armenians were under the influence of the Sasanian marzpans during this period.

The marzban was invested with supreme power, even imposing death sentences; but he could not interfere with the age-long privileges of the Armenian nakharars. The country as a whole enjoyed considerable autonomy. The office of Hazarapet, corresponding to that of Minister of the Interior, public works and finance, was mostly entrusted to an Armenian, while the post of Sparapet (commander-in-chief) was only entrusted to an Armenian. Each nakharar had his own army, according to the extent of his domain. The "National Cavalry" or "Royal force" was under the Commander-in-chief.

The Hephthalites were originally vassals of the Rouran Khaganate but split from their overlords in the early fifth century. The next time they were mentioned was in Persian sources as foes of Yazdegerd II, who from 442, fought 'tribes of the Hephthalites', according to the Armenian Elisee Vardaped.

In 453, Yazdegerd moved his court east to deal with the Hephthalites or related groups.

In 458, a Hephthalite king called Akhshunwar helped the Sasanian Emperor Peroz I gain the Persian throne from his brother. Before his accession to the throne, Peroz had been the Sasanian for Sistan in the far east of the Empire, and therefore had been one of the first to enter into contact with the Hephthalites and request their help.

The Hephthalites may have also helped the Sasanians to eliminate another Hunnic tribe, the Kidarites: by 467, Peroz I, with Hephthalite aid, reportedly managed to capture Balaam and put an end to Kidarite rule in Transoxiana once and for all. The weakened Kidarites had to take refuge in the area of Gandhara.

The Battle of Avarayr was fought on 2 June 451 on the Avarayr Plain in Vaspurakan between a Christian Armenian army under Vardan Mamikonian and Sassanid Persia. It is considered one of the first battles in defense of the Christian faith. Although the Persians were victorious on the battlefield, it was a pyrrhic victory as Avarayr paved the way to the Nvarsak Treaty of 484, which affirmed Armenia's right to practise Christianity freely. The battle is seen as one of the most significant events in Armenian history.

From 474 CE, Peroz I fought three wars with his former allies the Hephthalites. In the first two, he himself was captured and ransomed. Following his second defeat, he has to offer thirty mules loaded with silver drachms to the Hephthalites, and also had to leave his son Kavad as a hostage.

In the third battle, at the Battle of Herat (484), he was vanquished by the Hepthalite king Kun-khi, and for the next two years the Hephthalites plundered and controlled the eastern part of the Sasanian Empire. From 474 until the middle of the 6th century, the Sasanian Empire paid tribute to the Hephthalites.

Bactria came under formal Hephthalite rule from that time. Taxes were levied by the Hephthalites over the local population: a contract in the Bactrian language from the archive of the Kingdom of Rob, has been found, which mentions taxes from the Hephthalites, requiring the sale of land in order to pay these taxes.

In 376, unmanageable numbers of Goths and other non-Roman people, fleeing from the Huns, entered the Empire. In 395, after winning two destructive civil wars, Theodosius I died, leaving a collapsing field army, and the Empire, still plagued by Goths, divided between the warring ministers of his two incapable sons. Further barbarian groups crossed the Rhine and other frontiers and, like the Goths, were not exterminated, expelled or subjugated. The armed forces of the Western Empire became few and ineffective, and despite brief recoveries under able leaders, central rule was never effectively consolidated.

By 476, the position of Western Roman Emperor wielded negligible military, political, or financial power, and had no effective control over the scattered Western domains that could still be described as Roman. Barbarian kingdoms had established their own power in much of the area of the Western Empire. In 476, the Germanic barbarian king Odoacer deposed the last emperor of the Western Roman Empire in Italy, Romulus Augustulus, and the Senate sent the imperial insignia to the Eastern Roman Emperor Flavius Zeno.

While its legitimacy lasted for centuries longer and its cultural influence remains today, the Western Empire never had the strength to rise again. The Eastern Roman, or Byzantine Empire, survived and although lessened in strength, remained for centuries an effective power of the Eastern Mediterranean.

Following their victory over Peroz I, the Hepthalites became protectors and benefactors of his son Kavad I, as Balash, a brother of Peroz took the Sasanian throne. In 488, a Hepthalite army vanquished the Sasanian army of Balash, and was able to put Kavad I on the throne.

In 496–498, Kavad I was overthrown by the nobles and clergy, escaped, and restored himself with a Hephthalite army. Joshua the Stylite reports numerous instances in which Kavadh led Hepthalite ("Hun") troops, in the capture of the city of Theodosiupolis of Armenia in 501–502, in battles against the Romans in 502–503, and again during the siege of Edessa in September 503.

Kavad I was the Sasanian King of Kings of Iran from 488 to 531, with a two or three-year interruption. A son of Peroz I (r. 459–484), he was crowned by the nobles to replace his deposed and unpopular uncle Balash.

Inheriting a declining empire where the authority and status of the Sasanian kings had largely ended, Kavad tried to reorganize his empire by introducing many reforms whose implementation was completed by his son and successor Khosrow I. They were made possible by Kavad's use of the Mazdakite preacher Mazdak leading to a social revolution that weakened the authority of the nobility and the clergy. Because of this, and the execution of the powerful king-maker Sukhra, Kavad was imprisoned in the Castle of Oblivion ending his reign. He was replaced by his brother Jamasp. However, with the aid of his sister and an officer named Siyawush, Kavad and some of his followers fled east to the territory of the Hephthalite king who provided him with an army. This enabled Kavad to restore himself to the throne in 498/9.

Bankrupted by this hiatus, Kavad applied for subsidies from the Byzantine emperor Anastasius I. The Byzantines had originally paid the Iranians voluntarily to maintain the defense of the Caucasus against attacks from the north. Anastasius refused the subsidies, which led Kavad to invade his domains, thus starting the Anastasian War. Kavad first seized Theodosiopolis and Martyropolis respectively, and then Amida after holding the city under siege for three months. The two empires made peace in 506, with the Byzantines agreeing to pay subsidies to Kavad for the maintenance of the fortifications on the Caucasus in return for Amida. Around this time, Kavad also fought a lengthy war against his former allies, the Hephthalites; by 513 he had re-taken the region of Khorasan from them.

In 528, war between the Sasanians and Byzantines erupted again, because of the Byzantines refusal to acknowledge Khosrow as Kavad's heir, and a dispute over Lazica. Although Kavad's forces suffered two notable losses at Dara and Satala, the war was largely indecisive, with both sides suffering heavy losses. In 531, while the Iranian army was besieging Martyropolis, Kavad died from an illness. He was succeeded by Khosrow I, who inherited a reinvigorated and mighty empire that equaled that of the Byzantines.

Because of the many challenges and issues Kavad successfully overcame, he is considered one of the most effective and successful kings to rule the Sasanian Empire.

The Anastasian War was fought from 502 to 506 between the Byzantine Empire and the Sasanian Empire. It was the first major conflict between the two powers since 440, and would be the prelude to a long series of destructive conflicts between the two empires over the next century.

The Iberian War was fought from 526 to 532 between the Byzantine Empire and the Sasanian Empire over the eastern Georgian kingdom of Iberia—a Sasanian client state that defected to the Byzantines. Conflict erupted among tensions over tribute and the spice trade.

The Sasanians maintained the upper hand until 530 but the Byzantines recovered their position in battles at Dara and Satala while their Ghassanid allies defeated the Sasanian-aligned Lakhmids. A Sasanian victory at Callinicum in 531 continued the war for another year until the empires signed the "Perpetual Peace".

Khosrow I was the Sasanian King of Kings of Iran from 531 to 579. He was the son and successor of Kavad I. Inheriting a reinvigorated empire at war with the Byzantines, Khosrow I made a peace treaty with them in 532, known as the Perpetual Peace, in which the Byzantine emperor Justinian I paid 11,000 pounds of gold to the Sasanians. Khosrow then focused on consolidating his power, executing conspirators, including his uncle Bawi. Dissatisfied with the actions of the Byzantine clients and vassals, the Ghassanids, and encouraged by the Ostrogoth envoys from Italy, Khosrow violated the peace treaty and declared war against the Byzantines in 540. He sacked the city of Antioch, bathed in the Mediterranean Sea at Seleucia Pieria, and held chariot races at Apamea where he made the Blue Faction—which was supported by Justinian—lose against the rival Greens. In 541, he invaded Lazica and made it an Iranian protectorate, thus initiating the Lazic War. In 545, the two empires agreed to halt the wars in Mesopotamia and Syria, while it waged on in Lazica. A truce was made in 557, and by 562 a Fifty-Year Peace Treaty was made.

In 572, Justin II, the successor of Justinian, broke the peace treaty and sent a Byzantine force into the Sasanian region of Arzanene. The following year, Khosrow besieged and captured the important Byzantine fortress-city of Dara, which drove Justin II insane. The war would last till 591, outliving Khosrow. Khosrow's wars were not only based in the west. To the east, in an alliance with the Göktürks, he finally put an end to the Hephthalite Empire, which had inflicted a handful of defeats on the Sasanians in the 5th-century, killing Khosrow's grandfather Peroz I. To the south, Iranian forces led by Wahrez defeated the Aksumites and conquered Yemen.

Khosrow I was known for his character, virtues and knowledge. During his ambitious reign, he continued his father's project of making major social, military, and economic reforms, promoting the welfare of the people, increasing state revenues, establishing a professional army, and founding or rebuilding many cities, palaces, and much infrastructure. He was interested in literature and philosophy, and under his reign, art and science flourished in Iran. He was the most distinguished of the Sasanian kings, and his name became, like that of Caesar in the history of Rome, a designation of the Sasanian kings. Due to his accomplishments, he was hailed as the new Cyrus.

At the time of his death, the Sasanian Empire had reached its greatest extent since Shapur II, stretching from Yemen in the west to Gandhara in the east. He was succeeded by his son Hormizd IV.

The Lazic War, also known as the Colchidian War was fought between the Byzantine Empire and the Sasanian Empire for control of the ancient Georgian region of Lazica. The Lazic War lasted for twenty years, from 541 to 562, with varying success and ended in a victory for the Persians, who obtained an annual tribute in exchange for ending the war.

After Kavad I, the Hephthalites seem to have shifted their attention away from the Sasanian Empire, and Kavad's successor Khosrow I (531–579) was able to resume an expansionist policy to the east. According to al-Tabari, Khosrow I managed, through his expansionsit policy, to take control of "Sind, Bust, Al-Rukkhaj, Zabulistan, Tukharistan, Dardistan, and Kabulistan" as he ultimately defeated the Hephthalites with the help of the First Turkic Khaganate, the Göktürks.

In 552, the Göktürks took over Mongolia, formed the First Turkic Khaganate, and by 558 reached the Volga. Circa 555–567, the Turks of the First Turkic Khaganate and the Sasanians under Khosrow I allied against the Hephthalites and defeated them after an eight-day battle near Qarshi, the Battle of Bukhara, perhaps in 557.

These events put an end to the Hephthalite Empire, which fragmented into semi-independent Principalities, paying tribute to either the Sasanians or the Turks, depending on the military situation. After the defeat, the Hephthalites withdrew to Bactria and replaced king Gatfar with Faghanish, the ruler of Chaghaniyan. Thereafter, the area around the Oxus in Bactria contained numerous Hephthalites principalities, remnants of the great Hephthalite Empire destroyed by the alliance of the Turks and the Sasanians.

The Sasanians and Turks established a frontier for their zones of influence along the Oxus river, and the Hephthalite Principalities functioned as buffer states between two Empires. But when the Hephthalites chose Faghanish as their king in Chaganiyan, Khosrow I crossed the Oxus and put the Principalities of Chaghaniyan and Khuttal under tribute.

The Byzantine–Sasanian War of 572–591 was a war fought between the Sasanian Empire of Persia and the Byzantine Empire. It was triggered by pro-Byzantine revolts in areas of the Caucasus under Persian hegemony, although other events also contributed to its outbreak. The fighting was largely confined to the southern Caucasus and Mesopotamia, although it also extended into eastern Anatolia, Syria, and northern Iran. It was part of an intense sequence of wars between these two empires which occupied the majority of the 6th and early 7th centuries. It was also the last of the many wars between them to follow a pattern in which fighting was largely confined to frontier provinces and neither side achieved any lasting occupation of enemy territory beyond this border zone. It preceded a much more wide-ranging and dramatic final conflict in the early 7th century.

In 557, Khosrow I allied with the Göktürks and defeated the Hephthalites. An agreement was established between Khosrow I and the Turkic Khagan Istämi which set the Oxus as the frontier between the two empires. However, in 588, the Turkic Khagan Bagha Qaghan (known as Sabeh/Saba in Persian sources), together with his Hephthalite subjects, invaded the Sasanian territories south of the Oxus, where they attacked and routed the Sasanian soldiers stationed in Balkh, and then proceeded to conquer the city along with Talaqan, Badghis, and Herat. They were finally repelled by the Sasanian general Vahram Chobin.

The First Perso-Turkic War was fought during 588–589 between the Sasanian Empire and Hephthalite principalities and its lord the Göktürks. The conflict started with the invasion of the Sasanian Empire by the Turks and ended with a decisive Sasanian victory and the reconquest of lost lands.

Khosrow II is considered to be the last great Sasanian king (shah) of Iran, ruling from 590 to 628, with an interruption of one year. Khosrow II was the son of Hormizd IV, and the grandson of Khosrow I. He was the last king of Iran to have a lengthy reign before the Muslim conquest of Iran, which began five years after his execution. He lost his throne, then recovered it with the help of the Byzantine emperor Maurice, and, a decade later, went on to emulate the feats of the Achaemenids, conquering the rich Roman provinces of the Middle East; much of his reign was spent in wars with the Byzantine Empire and struggling against usurpers such as Bahram Chobin and Vistahm.

After the Byzantines killed Maurice, Khosrow II began a war in 602 against the Byzantines. Khosrow II's forces captured much of the Byzantine Empire's territories, earning the king the epithet "the Victorious". A siege of the Byzantine capital of Constantinople in 626 was unsuccessful, and Heraclius, now allied with Turks, started a risky but successful counterattack deep into Persia's heartland. Supported by the feudal families of the empire, Khosrow II's imprisoned son Sheroe (Kavad II) imprisoned and killed Khosrow II. This led to a civil war and interregnum in the empire and the reversal of all Sasanian gains in the war against the Byzantines.

The Byzantine–Sasanian War of 602–628 was the final and most devastating of the series of wars fought between the Byzantine Empire and the Sasanian Empire of Iran. The previous war between the two powers had ended in 591 after Emperor Maurice helped the Sasanian king Khosrow II regain his throne. In 602 Maurice was murdered by his political rival Phocas. Khosrow proceeded to declare war, ostensibly to avenge the death of the deposed emperor Maurice. This became a decades-long conflict, the longest war in the series, and was fought throughout the Middle East: in Egypt, the Levant, Mesopotamia, the Caucasus, Anatolia, Armenia, the Aegean Sea and before the walls of Constantinople itself.

While the Persians proved largely successful during the first stage of the war from 602 to 622, conquering much of the Levant, Egypt, several islands in the Aegean Sea and parts of Anatolia, the ascendancy of the emperor Heraclius in 610 led, despite initial setbacks, to a status quo ante bellum. Heraclius' campaigns in Iranian lands from 622 to 626 forced the Persians onto the defensive, allowing his forces to regain momentum. Allied with the Avars and Slavs, the Persians made a final attempt to take Constantinople in 626, but were defeated there. In 627, allied with Turks, Heraclius invaded the heartland of Persia. A civil war broke out in Persia, during which the Persians killed their king, and sued for peace.

By the end of the conflict, both sides had exhausted their human and material resources and achieved very little. Consequently, they were vulnerable to the sudden emergence of the Islamic Rashidun Caliphate, whose forces invaded both empires only a few years after the war. The Muslim armies swiftly conquered the entire Sasanian Empire as well as the Byzantine territories in the Levant, the Caucasus, Egypt, and North Africa. In the following centuries, the Byzantine and Arab forces would fight a series of wars for control of the Near East.

The Second Perso-Turkic War began in 606/607 with an invasion of the Sasanian Empire by the Göktürks and Hephthalites. The war ended in 608 with the defeat of the Turks and Hephthalites by the Sasanians under the Armenian general Smbat IV Bagratuni.

The Sasanian conquest of Jerusalem occurred after a brief siege of the city by the Sasanian military in 614 CE, and was a significant event in the Byzantine–Sasanian War of 602–628 that took place after the Sasanian king Khosrow II appointed his spahbod (army chief), Shahrbaraz, to take control of the Byzantine-ruled areas of the Near East for the Sasanian Persian Empire. Following the Sasanian victory in Antioch a year earlier, Shahrbaraz had successfully conquered Caesarea Maritima, the administrative capital of the Byzantine province of Palaestina Prima. By this time, the grand inner harbour had silted up and was useless; however, the Byzantine emperor Anastasius I Dicorus had reconstructed the outer harbour, and Caesarea Maritima remained an important maritime city. The city and its harbour gave the Sasanian Empire strategic access to the Mediterranean Sea.

Following the outbreak of a Jewish revolt against the Byzantine emperor Heraclius, the Sasanian Persians were joined by the Jewish leaders Nehemiah ben Hushiel and Benjamin of Tiberias, who enlisted and armed Jewish rebels from Tiberias, Nazareth and the mountain cities of the Galilee as well as from other parts of the southern Levant, after which they marched on the city of Jerusalem with the Sasanian military. Some 20,000–26,000 Jewish rebels joined the war against the Byzantine Empire. The joint Jewish–Sasanian force later captured Jerusalem; this occurred either without resistance: 207 or after a siege and breaching of the wall with artillery, depending on the source.

By 615, the Persians had driven the Romans out of northern Mesopotamia, Syria, and Palestine. Determined to eradicate Roman rule in Asia, Khosrow turned his sights on Egypt, the Eastern Roman Empire's granary.

The Sasanian conquest of Egypt took place between 618 and 621 CE, when the Sasanian Persian army defeated the Byzantine forces in Egypt and occupied the province. The fall of Alexandria, the capital of Roman Egypt, marked the first and most important stage in the Sasanian campaign to conquer this rich province, which eventually fell completely under Persian rule within a couple of years.

In 622, the Byzantine emperor Heraclius, was ready to mount a counter-offensive against the Sassanid Persians who had overrun most of the eastern provinces of the Byzantine Empire. He left Constantinople the day after celebrating Easter on Sunday, 4 April 622. His young son, Heraclius Constantine, was left behind as regent under the charge of Patriarch Sergius and the patrician Bonus. In order to threaten both the Persian forces in Anatolia and Syria, his first move was to sail from Constantinople to Pylae in Bithynia (not in Cilicia). He spent the summer training so as to improve the skills of his men and his own generalship. In the autumn, Heraclius threatened the Persian communications to Anatolia from the Euphrates valley by marching to northern Cappadocia. This forced the Persian forces in Anatolia under Shahrbaraz to retreat from the front-lines of Bithynia and Galatia to eastern Anatolia in order to block his access to Persia.

What followed next is not entirely clear, but Heraclius certainly won a crushing victory over Shahrbaraz somewhere in Cappadocia. The key factor was Heraclius' discovery of hidden Persian forces in ambush and responding to this ambush by feigning retreat during the battle. The Persians left their cover to chase the Byzantines, whereupon Heraclius' elite Optimatoi assaulted the chasing Persians, causing them to flee.

The siege of Constantinople in 626 by the Sassanid Persians and Avars, aided by large numbers of allied Slavs, ended in a strategic victory for the Byzantines. The failure of the siege saved the empire from collapse, and, combined with other victories achieved by Emperor Heraclius the previous year and in 627, enabled Byzantium to regain its territories and end the destructive Roman–Persian Wars by enforcing a treaty with borders status quo c. 590.

Following the First Siege of Constantinople by the Avars and Persians, the beleaguered Byzantine Emperor Heraclius found himself politically isolated. He could not rely on the Christian Armenian potentates of Transcaucasia, since they were branded as heretics by the Orthodox Church, and even the king of Iberia preferred to befriend the religiously tolerant Persians. Against this dismal background, he found a natural ally in Tong Yabghu. Earlier in 568, the Turks under Istämi had turned to Byzantium when their relations with Persia soured over commerce issues. Istämi sent an embassy led by the Sogdian diplomat Maniah directly to Constantinople, which arrived in 568 and offered not only silk as a gift to Justin II, but also proposed an alliance against Sassanid Persia. Justin II agreed and sent an embassy to the Turkic Khaganate, ensuring the direct Chinese silk trade desired by the Sogdians.

In 625, Heraclius dispatched to the steppes his emissary, named Andrew, who promised to the Khagan some "staggering riches" in return for military aid. The khagan, on his part, was anxious to secure the Chinese-Byzantine trade along the Silk Route, which had been disrupted by the Persians in the aftermath of the Second Perso-Turkic War. He sent word to the Emperor that "I shall take revenge on your enemies and will come with my valiant troops to your help". A unit of 1,000 horsemen fought their way through Persian Transcaucasia and delivered the Khagan's message to the Byzantine camp in Anatolia.

The Third Perso-Turkic War was the third and final conflict between the Sassanian Empire and the Western Turkic Khaganate. Unlike the previous two wars, it was not fought in Central Asia, but in Transcaucasia. Hostilities were initiated in 627 AD by Tong Yabghu Qaghan of the Western Göktürks and Emperor Heraclius of the Byzantine Empire. Opposing them were the Sassanid Persians, allied with the Avars. The war was fought against the background of the last Byzantine-Sassanid War and served as a prelude to the dramatic events that changed the balance of powers in the Middle East for centuries to come.

In April 630 Böri Shad determined to expand his control of Transcaucasia and sent his general Chorpan Tarkhan with as little as 30,000 cavalry to invade Armenia. Using a characteristic ploy of nomadic warriors, Chorpan Tarkhan ambushed and annihilated a Persian force of 10,000 dispatched by Shahrbaraz to counter the invasion. The Turks knew the Sassanid response would be harsh, and so they plundered cities and withdrew their forces back to the steppes.

The Battle of Nineveh was the climactic battle of the Byzantine-Sassanid War of 602–628. In mid-September 627, Heraclius invaded Sasanian Mesopatamia in a surprising, risky winter campaign. Khosrow II appointed Rhahzadh as the commander of an army to confront him. Heraclius' Göktürk allies quickly deserted, while Rhahzadh's reinforcements did not arrive in time. In the ensuing battle, Rhahzadh was slain and the remaining Sasanians retreated. The Byzantine victory later resulted in civil war in Persia, and for a period of time restored the (Eastern) Roman Empire to its ancient boundaries in the Middle East. The Sasanian civil war significantly weakened the Sasanian Empire, contributing to the Islamic conquest of Persia.

The Sasanian civil war of 628–632, also known as the Sasanian Interregnum was a conflict that broke out after the execution of the Sasanian king Khosrau II between the nobles of different factions, notably the Parthian (Pahlav) faction, the Persian (Parsig) faction, the Nimruzi faction, and the faction of general Shahrbaraz. Rapid turnover of rulers and increasing provincial landholder power further diminished the empire. Over a period of 4 years and 14 successive kings, the Sasanian Empire weakened considerably, and the power of the central authority passed into the hands of its generals, contributing to its fall.

The rise of the Muslims in Arabia coincided with an unprecedented political, social, economic, and military weakness in Persia. Once a major world power, the Sassanid Empire had exhausted its human and material resources after decades of warfare against the Byzantine Empire. The Sassanid state's internal political situation quickly deteriorated after the execution of King Khosrow II in 628. Subsequently, ten new claimants were enthroned within the next four years. Following the Sassanid Civil War of 628–632, the empire was no longer centralized.

Arab Muslims first attacked Sassanid territory in 633, when Khalid ibn al-Walid invaded Mesopotamia, which was the political and economic centre of the Sassanid state. Following the transfer of Khalid to the Byzantine front in the Levant, the Muslims eventually lost their holdings to Sassanid counterattacks. The second Muslim invasion began in 636, under Sa'd ibn Abi Waqqas, when a key victory at the Battle of al-Qadisiyyah led to the permanent end of Sassanid control west of modern-day Iran. For the next six years, the Zagros Mountains, a natural barrier, marked the border between the Rashidun Caliphate and the Sassanid Empire. In 642, Umar ibn al-Khattab, then-Caliph of the Muslims, ordered a full-scale invasion of Persia by the Rashidun army, which led to the complete conquest of the Sassanid Empire by 651. Directing from Medina, a few thousand kilometres away, Umar's quick conquest of Persia in a series of well-coordinated, multi-pronged attacks became his greatest triumph, contributing to his reputation as a great military and political strategist. In 644, prior to the complete annexation of Persia by the Arab Muslims, Umar was assassinated by Abu Lu'lu'a Firuz, a Persian craftsman who was captured in battle and brought to Arabia as a slave.

By 651, most of the urban centres in Iranian lands, with the notable exception of the Caspian provinces (Tabaristan and Transoxiana), had come under the domination of Arab Muslim forces. Many localities fought against the invaders; although Arabs had established hegemony over most of the country, many cities rose in rebellion by killing their Arab governors or attacking their garrisons. Eventually, Arab military reinforcements quashed the Iranian insurgencies and imposed complete Islamic control. The Islamization of Iran was gradual and incentivized in various ways over a period of centuries with some Iranians never converting and widespread cases of Zoroastrian scriptures being burnt and priests being executed, particularly in areas that experienced violent resistance.

The Battle of al-Qadisiyyah was fought between the Rashidun Caliphate and the Sasanian Empire. It occurred during the early Muslim conquests and marked a decisive victory for the Rashidun army during the Muslim conquest of Persia.

The Rashidun offensive at Qadisiyyah is believed to have taken place in November of 636; at the time, the Sasanian army was led by Rostam Farrokhzad, who died in uncertain circumstances during the battle. The collapse of the Sasanian army in the region led to a decisive Arab victory over the Iranians, and the incorporation of territory that comprises modern-day Iraq into the Rashidun Caliphate.

Arab successes at Qadisiyyah were key to the later conquest of the Sasanian province of Asoristan, and were followed by major engagements at Jalula and Nahavand. The battle allegedly saw the establishment of an alliance between the Sasanian Empire and the Byzantine Empire, with claims that the Byzantine emperor Heraclius married off his granddaughter Manyanh to the Sasanian king Yazdegerd III as a symbol of the alliance.

The Battle of Nahavand was fought in 642 between the Rashidun Muslim forces under caliph Umar and Sasanian Persian armies under King Yazdegerd III. Yazdegerd escaped to the Merv area, but was unable to raise another substantial army. It was a victory for the Rashidun Caliphate and the Persians consequently lost the surrounding cities including Spahan (Isfahan). The former Sassanid provinces, in alliance with Parthian and White Hun nobles, resisted for about a century in the region south of the Caspian Sea, even as the Rashidun Caliphate was replaced by the Umayyads, thus perpetuating the Sassanid court styles, Zoroastrian religion, and Persian language.

Upon hearing of the defeat in Nihawānd, Yazdegerd along with Farrukhzad and some of the Persian nobles fled further inland to the eastern province of Khorasan. Yazdegerd was assassinated by a miller in Merv in late 651. His sons, Peroz and Bahram, fled to Tang China. Some of the nobles settled in Central Asia, where they contributed greatly to spreading the Persian culture and language in those regions and to the establishment of the first native Iranian Islamic dynasty, the Samanid dynasty, which sought to revive Sassanid traditions.

The abrupt fall of the Sassanid Empire was completed in a period of just five years, and most of its territory was absorbed into the Islamic caliphate; however, many Iranian cities resisted and fought against the invaders several times. Islamic caliphates repeatedly suppressed revolts in cities such as Rey, Isfahan, and Hamadan. The local population was initially under little pressure to convert to Islam, remaining as dhimmi subjects of the Muslim state and paying a jizya. In addition, the old Sassanid "land tax" (known in Arabic as Kharaj) was also adopted. Caliph Umar is said to have occasionally set up a commission to survey the taxes, to judge if they were more than the land could bear.

The influence of the Sasanian Empire continued long after it fell. The empire, through the guidance of several able emperors prior to its fall, had achieved a Persian renaissance that would become a driving force behind the civilization of the newly established religion of Islam. In modern Iran and the regions of the Iranosphere, the Sasanian period is regarded as one of the high points of Iranian civilization.

In Europe

Sasanian culture and military structure had a significant influence on Roman civilization. The structure and character of the Roman army was affected by the methods of Persian warfare. In a modified form, the Roman Imperial autocracy imitated the royal ceremonies of the Sasanian court at Ctesiphon, and those in turn had an influence on the ceremonial traditions of the courts of medieval and modern Europe.

In Jewish history

Important developments in Jewish history are associated with the Sassanian Empire. The Babylonian Talmud was composed between the third and sixth centuries in Sasanian Persia and major Jewish academies of learning were established in Sura and Pumbedita that became cornerstones of Jewish scholarship.

In India

The collapse of the Sasanian Empire led to Islam slowly replacing Zoroastrianism as the primary religion of Iran. A large number of Zoroastrians chose to emigrate to escape Islamic persecution. According to the Qissa-i Sanjan, one group of those refugees landed in what is now Gujarat, India, where they were allowed greater freedom to observe their old customs and to preserve their faith. The descendants of those Zoroastrians would play a small but significant role in the development of India. Today there are over 70,000 Zoroastrians in India.