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Sassanid Empire


Sassanid Empire or Sassanian Dynasty is the name used for the third Iranian dynasty and the second Empire. The dynasty was founded by Ardashir I after defeating the last Parthian (Arsacid) king, Artabanus IV Ardavan). It ended when the last Sassanid Shahanshah (King of Kings), Yazdegerd III (632-651), lost a 14-year struggle to drive out the expanding Islamic empires. The Empire's territory encompassed all of what is now Iran, Iraq, Armenia, Afghanistan, eastern parts of Turkey, and parts of Syria, Pakistan, Caucasia, Central Asia and Arabia. The Sassanids called their empire Eranshahr "Empire of the Aryans (Persians)". The Sassanid era is considered to be one of Iran's most important and influential historical periods. In many ways the Sassanid period witnessed the highest achievement of Persian civilization, constituting the last great Iranian Empire before the Muslim conquest. Persia influenced Roman civilization considerably during the Sassanids' times, and the Romans reserved for the Sassanid Persians alone the status of equals.

Often tolerant of religious minorities, Jewish life flourished during the Sassanid period, producing the Babylonian Talmud. Their cultural influence extended far beyond the empire's territorial borders, reaching Western Europe, Africa, China and India and played a prominent role in the formation of European and Asiatic medieval art. This influence carried forward to the early Islamic world with the Muslim conquest of Iran, including the idea of a paid, professional army. Although often engaged in conquest, the Sassanids also entered into peace treaties and engaged in widespread trade. They served humanity as cultural catalysts, helping to create a more interconnected and inter-dependent world.


Origins and early history (205-310)

Ghal'eh Dokhtar (or "The Maiden's Castle") in present-day Fars, Iran, built by Ardashir in 209, before he was finally able to defeat the Parthian empire.

Scanty and conflicting stories obscure the end of the Arsacids and the rise of the Sassanids.1 The Sassanid Dynasty was established by Ardashir I, a descendant of a line of the priests of goddess Anahita in Istakhr, who was governor of Persis at the start of the third century. However, his ancestry is a little vague, since it is unclear whether he was a natural or adopted son of Papag, and whether Sasan was the eponymous founder of the dynasty or Ardashir's real father or father-in-law. In general, sources are not consistent about the relationships between the early Sassanids, Sassan, Papag, Ardashir and Shapur.2

Papag was originally the ruler of a small town called Kheir, but by 200 C.E. had deposed Gocihr, the last king of the Bazrangids (the local rulers of Persis as a client of the Arsacids) and appointed himself as ruler. His mother, Rodhagh, was the daughter of the provincial governor of Persis. Papag and his eldest son Shapur expanded their power over all of Persis. The subsequent events are unclear, due to the sketchy nature of the sources. It is certain, though, that following the death of Pabag, Ardashir who was then governor of Darabgird, became involved in a power struggle of his own with his elder brother Shapur. The sources tell us 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 Persis.3

Moving his capital further to the south of Persis, Ardashir founded Ardashir-Khwarrah (formerly Gur, modern day Firouzabad). The city, well supported by high mountains and east to defend through narrow passes, became the center of Ardashir's efforts to gain more power. The city was surrounded by a high, circular wall, probably copied from Darabgird's; on the north-side was a large palace, remains of which still survive. After establishing his rule over Persis, Ardashir I rapidly extended his territory, demanding fealty from the local princes and gaining control over the neighboring provinces of Kerman, Isfahan, Susiana, and Mesene. When this expansion came to the attention of Artabanus IV, the Parthian king, he ordered the governor of Khuzestan to march against Ardashir in 224. This resulted in a major victory for Ardashir. Artabanus himself marched against Ardashir I in 224. Their armies clashed at Hormozgan, where Artabanus was killed and Ardashir I went on to invade the western provinces of the now defunct Parthian Empire.

The Humiliation of Valerian by Shapur (Hans Holbein the Younger, 1521, pen and black ink on a chalk sketch, Kunstmuseum Basel).

A dynastic struggle for the Parthian throne at the time helped Ardashir consolidate his authority in the south with little or no interference. This was also assisted by the geography of the Fars province, which was separate from the rest of Iran,4 Crowned in 224 at Ctesiphon as the sole ruler of Persia, Ardashir took the title Shahanshah, or "King of Kings" (the inscriptions mention Adhur-Anahid as his "Queen of Queens," but her relationship with Ardashir is not established). Thus 400-years of Parthian rule ended and four centuries of Sassanid rule began.5

Over the next few years, following local rebellions around the empire, Ardashir I further expanded his empire to the east and northwest, conquering the provinces of Sistan, Gorgan, Khorasan, Margiana (in modern Turkmenistan), Balkh, and Chorasmia. He also added Bahrain and Mosul to Sassanid possessions. Later Sassanid inscriptions also claim the submission of the Kings of Kushan, Turan, and Mekran to Ardashir, although based on numismatic evidence, it is more likely that these actually submitted to Ardashir's son, the future Shapur I. In the west, assaults against Hatra, Kingdom of Armenia, and Adiabene met with less success. In 230 he raided deep into Roman territory, and a Roman counter-offensive two years later ended inconclusively, although the Roman emperor, Alexander Severus, celebrated a triumph in Rome.6

Ardashir I's son Shapur I continued to expand the empire, conquering Bactria and the western portion of the Kushan Empire and led several campaigns against Rome. Invading Roman Mesopotamia, Shapur I captured Carrhae and Nisibis, but in 243 the Roman general Timesitheus defeated the Persians at Rhesaina and regained the lost territories.7 The emperor Gordian III's (238-244) subsequent advance down the Euphrates was defeated at Meshike (244), leading to Gordian's murder by his own troops and enabling Shapur to conclude a highly advantageous peace treaty with the new emperor Philip the Arab, by which he secured the immediate payment of 500,000 denari and further annual payments. Shapur soon resumed the war, defeated the Romans at Barbalissos (252), and then probably took and plundered Antioch.7 Roman counter-attacks under the emperor Valerian ended in disaster when the Roman army was defeated and besieged at Edessa and Valerian was captured by Shapur, remaining his prisoner for the rest of his life. Shapur celebrated his victory by carving the impressive rock reliefs in Naqsh-e Rostam and Bishapur, as well as a monumental inscription in Persian and Greek in the vicinity of Persepolis. He exploited his success by advancing into Anatolia (260), but withdrew in disarray after defeats at the hands of the Romans and their Palmyrene ally Odaenathus, suffering the capture of his harem and the loss of all the Roman territories he had occupied.8

Coin of Hormizd I, issued in Afghanistan, and derived from Kushan designs

Shapur had intensive development plans; he 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 favored Manichaeism, protected Mani (who dedicated one of his books, the "Shabuhragan," to him) and sent many Manichaean missionaries abroad. He also befriended a Babylonian rabbi called Shmuel. This friendship was advantageous for the Jewish community and gave them a respite from the oppressive laws enacted against them. Later kings reversed Shapur's policy of religious tolerance. Under pressure from Zoroastrian Magi and influenced by the high-priest Kartir, Bahram I killed Mani and persecuted his followers. Bahram II was, like his father, amenable to the wishes of the Zoroastrian priesthood.9 During his reign the Sassanid capital Ctesiphon was sacked by the Romans under emperor Carus, and most of Armenia, after half a century of Persian rule, was ceded to Diocletian.10

Succeeding Bahram III (who ruled briefly in 293), Narseh embarked on another war with the Romans. After an early success against the Emperor Galerius near Callinicum on the Euphrates in 296, Narseh was decisively defeated in an ambush while he was with his harem in Armenia in 298. In the treaty that concluded this war, the Sassanids ceded five provinces east of the Tigris and agreed not to interfere in the affairs of Armenia and Georgia.11 Following this crushing defeat, Narseh resigned in 301 and died in grief a year later. Narseh's son Hormizd II suppressed revolts in Sistan and Kushan, but was unable to control the nobles; he was killed by Bedouins while hunting in 309.

First Golden Era (309-379)

Following Hormizd II's death, Arabs from the south started to ravage and plunder the southern cities of the empire, even attacking the province of Fars, the birthplace of the Sassanid kings. Meanwhile, Persian nobles killed Hormizd II's eldest son, blinded the second, and imprisoned the third (who later escaped to Roman territory). The throne was reserved for Shapur II, the unborn child of one of Hormizd II's wives, who was crowned in utero: the crown was placed upon his mother's stomach. Until Shapur II came of age, the empire was controlled by his mother and the nobles. Once he assumed power, he quickly proved to be an active and effective ruler.

Shapur II first led his small but disciplined army south against the Arabs, whom he defeated, securing the southern areas of the empire.12 He then started his first campaign against the Romans in the west, where Persian forces won a series of battles but were unable to make territorial gains due to the failure of repeated sieges of the key frontier city of Nisibis and Roman success in retaking the cities of Singara and Amida after they fell to the Persians. These campaigns were halted by nomadic raids along the eastern borders of the empire, which threatened Transoxiana, a strategically critical area for control of the Silk Road. Shapur therefore marched east toward Transoxiana to meet the eastern nomads, leaving his local commanders to mount nuisance raids on the Romans. He crushed the Central Asian tribes, and annexed the area as a new province. He completed the conquest of the area now known as Afghanistan. Cultural flourished followed this victory, and Sassanid art penetrated Turkistan, reaching as far as China. Shapur, along with the nomad King Grumbates, started his second campaign against the Romans in 359, and soon succeeded in taking Singara and Amida again. In response to this, the Roman emperor Julian struck deep into Persian territory, and defeated Shapur's forces at Ctesiphon. However, having failed to take the capital, he was killed while trying to retreat back to Roman territory. His successor Jovian, trapped on the east bank of the Tigris, had to agree to hand over all the provinces which the Persians had ceded to Rome in 298 as well as Nisibis and Singara, in order to secure safe conduct for his army out of Persia.

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 Persian Empire was stronger than ever, with its enemies to the east pacified and Armenia under Persian control.

Intermediate Era (379-498)

Asia in 400 C.E., the Sassanid Empire, Roman Empire, the Kidarites, and Indo-Sassanid KushanshahsBahram Gur is a great favorite in Persian literature and poetry. "Bahram and the Indian princess in the black pavilion." Depiction of a Khamsa (Quintet) by the great Persian poet Nizami, mid-sixteenth-century Safavid era

From Shapur II's death until Kavadh I's first coronation was a largely peaceful period with the Romans, interrupted only by two brief wars, the first in 421-422 and the second in 440.13 Throughout this era Sassanid religious policy differed dramatically from king to king. Despite a series of weak leaders, the administrative system established during Shapur II's reign remained strong, and the empire continued to function effectively.

Shapur II died in 379, leaving a powerful empire to his half-brother Ardashir II (379-383; son of Vahram of Kushan) and his son Shapur III (383-388). Neither demonstrated their predecessor's talent. Bahram IV (388 - 399), although not as inactive as his father, still failed to achieve anything of significance for the empire. During this time Armenia was divided by treaty between the Roman and Sassanid empires, the Sassanids reestablished their rule over Greater Armenia, with the Byzantine Empire holding a small portion of western Armenia.

Bahram IV's son Yazdegerd I (399-421) is often compared to Constantine I. Like him, he was physically and diplomatically powerful and an opportunist. Like Constantine the Great, Yazdgerd I practiced religious tolerance and provided freedom for the rise of religious minorities. He stopped the persecution of Christians and even punished nobles and priests who persecuted them. His reign marked a relatively peaceful era. He made lasting peace with the Romans and even took the young Theodosius II (408-450) under his guardianship. He also married a Jewish princess who bore him a son called Narsi.

Yazdegerd I's successor was his son Bahram V (421-438), one of the most well-known Sassanid kings and the hero of many myths which persisted even after the destruction of the Sassanid empire. Bahram V, better known as Bahram-e Gur, gained the crown after Yazdgerd I's sudden death (or assassination) against the opposition of the grandees with the help of al-Mundhir, the Arabic dynast of al-Hirah. Bahram V's mother was Soshandukht, the daughter of the Jewish Exilarch. In 427 he crushed an invasion in the east by the nomadic Hephthalites, extending his influence into Central Asia, where his portrait survived for centuries on the coinage of Bukhara (in modern Uzbekistan). Bahram V deposed the vassal King of the Persian part of Armenia and made it a province.

Persian tradition relates many stories of Bahram V's valor, beauty, of his victories over the Romans, Turks, Indians and Africans, and of his adventures in hunting and in love. He is called Bahram-e Gur, Gur meaning Onager (an Asiatic wild ass), on account of his love for hunting and, in particular, hunting onagers. He symbolized a king in the height of a golden age. He had won his crown by competing with his brother and spent time fighting foreign enemies, but mostly kept himself amused by hunting and court parties with his famous band of ladies and courtiers. He embodied royal prosperity. During his time the best pieces of Sassanid literature were written, notable pieces of Sassanid music were composed, and sports such as polo became royal pastimes.

A coin of Yazdegerd II.

Bahram V's son Yazdegerd II (438 - 457) was a just, moderate ruler but, in contrast to Yazdegerd I, practiced a harsh policy towards minority religions, particularly Christianity.14 At the beginning of his reign, Yazdegerd II gathered a mixed army of various nations, including his Indian allies, and attacked the Eastern Roman Empire in 441, but peace was soon restored after small-scale fighting. He then gathered his forces in Neishabur in 443 and launched a prolonged campaign against the Kidarites. Finally after a number of battles, he crushed the Kidarites and drove them out beyond Oxus river in 450.15

During his eastern campaign, Yazdegerd II grew suspicious of the Christians in the army and expelled them all from the governing body and army. He then persecuted the Christians and, to a much lesser extent, the Jews.16 In order to reestablish Zoroastrianism in Armenia, he crushed an uprising of Armenian Christians at the Battle of Vartanantz in 451. The Armenians, however, remained primarily Christian. In his later years, he was engaged yet again with Kidarites until his death in 457. Hormizd III (457 - 459), younger son of Yazdegerd II, ascended to the throne. During his short rule, he continually fought with his elder brother Peroz, who had the support of nobility16 and with the Hephthalites in Bactria. Peroz killed him in 459.

In the beginning of the fifth century, the Hephthalites (White Huns), along with other nomadic groups, attacked Persia. At first Bahram V and Yazdegerd II inflicted decisive defeats against them and drove them back eastward. The Huns returned at the end of fifth century and defeated Peroz I (457-484) in 483. Following this victory the Huns invaded and plundered parts of eastern Persia for two years, exacting tribute for several years.

These attacks brought instability and chaos to the kingdom. Peroz I tried again to drive out the Hephthalites, but on the way to Herat, he and his army were trapped by the Huns in the desert. Peroz I was killed and his army wiped out. After this victory the Hephthalites advanced to the city of Herat, throwing the empire into chaos. Eventually, a noble Persian from the old family of Karen, Zarmihr (or Sokhra), restored some degree of order. He raised Balash, one of Peroz I's brothers, to the throne, although the Hunnic threat persisted until the reign of Khosrau I. Balash (484-488) was a mild and generous monarch, who made concessions to the Christians; however, he took no action against the empire's enemies, particularly, the White Huns. Balash, after a reign of four years, was blinded and deposed (attributed to magnates), and his nephew Kavadh I became emperor.

Kavadh I (488-531) was an energetic and reformist ruler. Kavadh I gave his support to the communistic sect founded by Mazdak, son of Bamdad, who demanded that the rich should divide their wives and their wealth with the poor. His intention evidently was, by adopting the doctrine of the Mazdakites, to break the influence of the magnates and the growing aristocracy. These reforms led to his deposition and imprisonment in the "Castle of Oblivion" (Lethe) in Susa, and his younger brother Jamasp (Zamaspes) was raised to the throne in 496. Kavadh I, however, escaped in 498 and was given refuge by the White Hun king.

Djamasp (496-498) was installed on the Sassanid throne after Kavadh I was deposed by members of the nobility. Djamasp reduced taxes to relieve the peasants and the poor. Unlike Kavadh I, he supported the mainstream Mazdean religion. His reign soon ended when Kavadh I, at the head of a large army loaned by the Hephthalite king, returned to the empire's capital. Djamasp stepped down from his position and restored the throne to his brother. Although Djamasp disappears from the records, it is widely believed that he was treated favorably at the court of his brother.

Second Golden Era (498-622)

The Sassanid Empire in 500 C.E. Map also shows borders of Hephthalite Khanate and the Eastern Roman Empire.Hunting scene on a gilded silver bowl showing king Khosrau I

The second golden era began after the second reign of Kavadh I. With the support of the Hephtalites, Kavadh I launched a campaign against the Romans. In 502, he took Theodosiopolis (Erzurum) in Modern Turkey, but lost it soon afterwards. In 503 he took Amida (Diarbekr) on the Tigris. In 504, an invasion of Armenia by the western Huns from the Caucasus led to an armistice, the return of Amida to Roman control and a peace treaty in 506. In 521/2 Kavadh lost control of Lazica, whose rulers switched their allegiance to the Romans; an attempt by the Iberians in 524/5 to do likewise triggered a war between Rome and Persia. In 527 a Roman offensive against Nisibis was repulsed and Roman efforts to fortify positions near the frontier were thwarted. In 530, Kavadh sent an army under Firouz the Mirranes to attack the important Roman frontier city of Dara. The army was met by the Roman general Belisarius, and though superior in numbers, was defeated at the Battle of Dara. In the same year, a second Persian army under Mihr-Mihroe was defeated at Satala by Roman forces under Sittas and Dorotheus, but in 531 a Persian army accompanied by a Lakhmid contingent under al-Mundhir IV defeated Belisarius at the Battle of Callinicum, and in 532 an "eternal" peace was concluded.17 Although he could not free himself from the yoke of the Ephthalites, Kavadh succeeded in restoring order in the interior and fought with general success against the Eastern Romans. He founded several cities, some of which were named after him and began to regulate the taxation and internal administration.

Kavadh I was succeeded by his son Khosrau I (531-579) also known as Anushirvan ("with the immortal soul"). One of the most celebrated Sassanid ruler, he is famous for reforming the aging Sassanid governing body by rationalizing taxation, based on a survey of landed possessions, which his father had begun. He also tried to increase the welfare and the revenues of his empire. Previous great feudal lords fielded their own military equipment, followers and retainers. Khosrau I developed a new force of dehkans or "knights" paid and equipped by the central government and the bureaucracy, tying the army and bureaucracy more closely to the central government than to local lords.

Although the Emperor Justinian I (527-565) had paid him a bribe of 440,000 pieces of gold to keep the peace, in 540 Khosrau I broke the "eternal peace" of 532 and invaded Syria, sacking the city of Antioch and extorting large sums of money from a number of other cities. Further successes followed: in 541 Lazica defected to the Persian side, and in 542 a major Byzantine offensive in Armenia was defeated at Anglon. A five-year truce agreed in 545 was interrupted in 547 when Lazica again switched sides and eventually expelled its Persian garrison with Byzantine help; the war resumed, but remained confined to Lazica, which was retained by the Byzantines when peace was concluded in 562.

In 565, Justinian I died and was succeeded by Justin II (565-578), who resolved to stop subsidies to Arab chieftains to restrain them from raiding Byzantine territory in Syria. A year earlier the Sassanid governor of Armenia built a fire temple at Dvin near modern Yerevan, and he put to death an influential member of the Mamikonian family, touching off a revolt which led to the massacre of the Persian governor and his guard in 571, while rebellion also broke out in Iberia. Justin II took advantage of the Armenian revolt to stop his yearly payments to Khosrau I for the defense of the Caucasus passes. The Armenians were welcomed as allies, and an army was sent into Sassanid territory to besiege Nisibis in 573. However, dissension among the Byzantine generals not only led to the siege's abandonment, but they in turn were besieged in the city of Dara, which was taken by the Persians. They then ravaged Syria, causing Justin II to agree to make annual payments in exchange for a five-year truce on the Mesopotamian front, although the war continued elsewhere. In 576 Khosrau I led his last campaign, an offensive into Anatolia which sacked Sebasteia and Melitene, but ended in disaster: defeated outside Melitene, the Persians suffered heavy losses as they fled across the Euphrates under Byzantine attack. Taking advantage of Persian disarray, the Byzantines raided deep into Khosrau's territory, even mounting amphibious attacks across the Caspian Sea. Khosrau sued for peace, but he decided to continue the war after a victory by his general Tamkhosrau in Armenia in 577 and fighting resumed in Mesopotamia. The Armenian revolt came to an end with a general amnesty, which brought Armenia back into the Sassanid Empire.

Asia in 600 C.E., showing the Sassanid Empire before the Arab conquest

Around 570 "Ma 'd-Karib," half-brother of the King of Yemen, requested Khosrau I's intervention. Khosrau I sent a fleet and a small army under a commander called Vahriz to the area near present Aden, and they marched against the capital San'a'l, which was occupied. Saif, son of Mard-Karib, who had accompanied the expedition, became King sometime between 575 and 577. Thus the Sassanids were able to establish a base in south Arabia to control the sea trade with the east. Later the south Arabian kingdom renounced Sassanid overlordship, and another Persian expedition was sent in 598 that successfully annexed southern Arabia as a Sassanid province, which lasted until the time of troubles after Khosrau II.

Khosrau I's reign witnessed the rise of the dihqans (literally, village lords), the petty landholding nobility who were the backbone of later Sassanid provincial administration and the tax collection system. Khosrau I was a great builder, embellishing his capital, founding new towns, and constructing new buildings. He rebuilt the canals and restocked the farms destroyed in the wars. He built strong fortifications at the passes and placed subject tribes in carefully chosen towns on the frontiers to act as guardians against invaders. He was tolerant of all religions, though he decreed that Zoroastrianism should be the official state religion, and was not unduly disturbed when one of his sons became a Christian.

The Sassanid Empire at its greatest extent, under king Khosrau II

After Khosrau I, Hormizd IV (579-590) took the throne. War with the Byzantines continued to rage intensely but inconclusively until the general Bahram Chobin, dismissed and humiliated by Hormizd, rose in revolt in 589. The following year Hormizd was overthrown by a palace coup and his son Khosrau II (590-628) placed on the throne, but this change of ruler failed to placate Bahram, who defeated Khosrau, forcing him to flee to Byzantine territory, and seized the throne for himself as Bahram VI. With the aid of troops provided by the Byzantine emperor Maurice (582-602), Khosrau II raised a new rebellion against Bahram, and the combined armies of Khosrau and the Byzantine generals Narses and John Mystacon won a decisive victory over Bahram at Ganzak (591), restoring Khosrau to power. In return for Maurice's help, Khosrau was obliged to return all Byzantine territory occupied during the war and to hand over control of the western parts of Armenia and Iberia.

When Maurice was overthrown and killed by Phocas (602-610) in 602, Khosrau II used his benefactor's murder as a pretext to begin a new invasion, which benefited from continuing civil war in the Byzantine Empire and met little effective resistance. Khosrau's generals systematically subdued the heavily fortified frontier cities of Byzantine Mesopotamia and Armenia, laying the foundations for unprecedented expansion. The Persians overran Syria and captured Antioch in 611. In 613, outside Antioch, the Persian generals Shahrbaraz and Shahin decisively defeated a major counter-attack led in person by the Byzantine emperor Heraclius. After this, the Persian advance continued unchecked. Jerusalem fell in 614, Alexandria in 619 and the rest of Egypt by 621. The Sassanid dream of restoring the Achaemenid boundaries was close to completion. A blossoming of art, music and architecture accompanied this peak of expansion. The Byzantine Empire was on the verge of collapse while the borders of the Achaemenid Empire were close to being restored on all fronts.

Decline and fall (622 - 651)

Queen Purandokht, daughter of Khosrau II, the last woman and one of the last rulers on the throne of the Sassanid dynasty, 630.

Although hugely successful at first glance, Khosrau II's campaign had overextended the Persian army and overtaxed the people. The Byzantine emperor Heraclius (610 - 641) drew on all his diminished and devastated empire's remaining resources, reorganized his armies and mounted a remarkable counter-offensive. Between 622 and 627 he campaigned against the Persians in Anatolia and the Caucasus, winning a string of victories against Persian forces under Khosrau, Shahrbaraz, Shahin and Shahraplakan, sacking the great Zoroastrian temple at Ganzak and securing assistance from the Khazars and Western Turkic Khaganate. In 626 Slavic and Avar forces sieged Constantinople supported by a Persian army under Shahrbaraz on the far side of the Bosphorus. However, the Byzantinen fleet blocked attempts to ferry the Persians across and the siege ended in failure. In 627-628 Heraclius mounted a winter invasion of Mesopotamia and, despite the departure of his Khazar allies, defeated a Persian army commanded by Rhahzadh in the Battle of Nineveh. Marching down the Tigris, he devastated the country and sacked Khosrau's palace of Dastagerd. He was prevented from attacking Ctesiphon by the destruction of the bridges on the Nahrawan Canal but conducted further raids before withdrawing up the Diyala river into north-western Iran.18

Heraclius' victories, the devastation of the richest territories of the Sassanid Empire and the humiliating destruction of high-profile targets such as Ganzak and Dastagerd fatally undermined Khosrau's prestige. Early in 628 he was overthrown and murdered by his son Kavadh II (628), who immediately brought an end to the war, agreeing to withdraw from all occupied territories. In 629 C.E. Heraclius restored the True Cross to Jerusalem in a majestic ceremony. Kavadh died within months and chaos and civil war followed. Over a period of four years and five successive kings, including a daughters of Khosrau II (Purandokht, queen 629-331), the Sassanid Empire weakened considerably as power passed into the hands of the generals. Purandokht renewed peace with Byzantium, lowered taxes but was unable to prevent the outbreak of civil war.19 It would take several years for a strong king to emerge from a series of coups, and the Sassanids never had