Sasanian Empire

Officially, the Sasanian Empire was known as the "Empire of the Iranians" (Middle Persian: 𐭠𐭩𐭥𐭠𐭭𐭱𐭲𐭥𐭩 Ērānšahr; Parthian: 𐭀𐭓𐭉𐭀𐭍𐭇𐭔𐭕𐭓 Aryānxšahr; Greek: Ἀριανῶν ἔθνος Arianōn Ethnos). The term is first attested in the trilingual Great Inscription of Shapur I, in which the king declares "I am the lord of the Empire of the Iranians."

More commonly, the empire, like the Sasanian dynasty itself, is named directly after Sasan in historical and academic sources. This term is variously recorded in English as the Sassanian Empire, the Sasanid Empire, and the Sassanid Empire.

Conflicting accounts shroud the details of the fall of the Parthian Empire and subsequent rise of the Sasanian Empire in mystery. The Sasanian 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 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 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 (formerly Gur, modern day Firuzabad). 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. It was surrounded by a high, circular wall, probably copied from that of Darabgerd. Ardashir's palace was on the north side of the city; remains of it are extant. After establishing his rule over Pars, Ardashir rapidly extended his territory, demanding fealty from the local princes of Pars, and gaining control over the neighboring provinces of Kerman, Isfahan, Susiana and Mesene. This expansion quickly came to the attention of Artabanus IV, 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. In a second attempt to destroy Ardashir, Artabanus himself met Ardashir in battle at Hormozgan, where the former met his death. Following the death of the Parthian ruler, Ardashir went on to invade the western provinces of the now defunct Parthian Empire.

At that time the Arsacid dynasty was divided between supporters of Artabanus IV and Vologases VI, which probably allowed Ardashir to consolidate his authority in the south with little or no interference from the Parthians. Ardashir was aided by the geography of the province of Pars, which was separated from the rest of Iran. 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 banbishnan banbishn, "Queen of Queens", but her relationship with Ardashir has not been fully established), bringing the 400-year-old Parthian Empire to an end, and beginning four centuries of Sassanid rule.

In the next few years, local rebellions occurred throughout the empire. Nonetheless, Ardashir I further expanded his new empire to the east and northwest, conquering the provinces of Sakastan, Gorgan, Khorasan, Marw (in modern Turkmenistan), Balkh and Chorasmia. He also added Bahrain and Mosul to the Sassanid possessions. Later Sassanid inscriptions also claim the submission of the kings of Kushan, Turan and Makuran 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, Armenia and Adiabene met with less success. In 230, Ardashir raided deep into Roman territory, and a Roman counter-offensive two years later ended inconclusively. Ardashīr began leading campaigns into Greater Khurasan as early as 233, extending his power to Khwarazm in the north and Sistan in the south while capturing lands from Gorgan to Abarshahr, Marw, and as far east as Balkh.

Ardashir I's son Shapur I continued the expansion of the empire, conquering Bactria and the western portion of the Kushan Empire, while leading 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. 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 denarii and further annual payments.

Shapur soon resumed the war, defeated the Romans at Barbalissos (253), and then probably took and plundered Antioch. 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. In 262 AD, Shapur attacked the Kushans destroying the cities of Begram and Taxila.

Shapur ordered the construction of the first dam bridge in Iran and founded many cities. 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.

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. When Shapur's son Bahram I acceded to the throne, he was pressured by the Zoroastrian high-priest Kartir Bahram I to kill Mani and persecute his followers. Bahram II was also amenable to the wishes of the Zoroastrian priesthood. During his reign, the Sasanian 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.

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, he was eventually decisively defeated by them. Galerius had been reinforced, probably in the spring of 298, by a new contingent collected from the empire's Danubian holdings. Narseh did not advance from Armenia and Mesopotamia, leaving Galerius to lead the offensive in 298 with an attack on northern Mesopotamia via Armenia. Narseh retreated to Armenia to fight Galerius's force, to the former's disadvantage: the rugged Armenian terrain was favourable to Roman infantry, but not to Sassanid cavalry. Local aid gave Galerius the advantage of surprise over the Persian forces, and, in two successive battles, Galerius secured victories over Narseh.

During the second encounter, Roman forces seized Narseh's camp, his treasury, his harem, and his wife. Galerius advanced into Media and Adiabene, winning successive victories, most prominently near Erzurum, and securing Nisibis (Nusaybin, Turkey) before 1 October 298. He then advanced down the Tigris, taking Ctesiphon. Narseh had previously sent an ambassador to Galerius to plead for the return of his wives and children. Peace negotiations began in the spring of 299, with both Diocletian and Galerius presiding.

The conditions of the peace were heavy: Persia would give up territory to Rome, making the Tigris the boundary between the two empires. Further terms specified that Armenia was returned to Roman domination, with the fort of Ziatha as its border; Caucasian Iberia would pay allegiance to Rome under a Roman appointee; Nisibis, now under Roman rule, would become the sole conduit for trade between Persia and Rome; and Rome would exercise control over the five satrapies between the Tigris and Armenia: Ingilene, Sophanene (Sophene), Arzanene (Aghdznik), Corduene, and Zabdicene (near modern Hakkâri, Turkey).

The Sasanians ceded five provinces west of the Tigris, and agreed not to interfere in the affairs of Armenia and Georgia. In the aftermath of this defeat, Narseh gave up the throne and died a year later, leaving the Sasanian throne to his son, Hormizd II. Unrest spread throughout the land, and while the new king suppressed revolts in Sakastan and Kushan, he was unable to control the nobles and was subsequently killed by Bedouins on a hunting trip in 309.

Following Hormizd II's death, northern Arabs started to ravage and plunder the western cities of the empire, even attacking the province of pars, the birthplace of the Sasanian kings. Meanwhile, Persian nobles killed Hormizd II's eldest son, blinded the second, and imprisoned the third (who later escaped into Roman territory). The throne was reserved for a younger son, Shapur II. During his youth the empire was controlled by his mother and the nobles. Upon coming of age, Shapur II assumed power and quickly proved to be an active and effective ruler.

He first led his small but disciplined army south against the Arabs, whom he defeated, securing the southern areas of the empire. He then began 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 had previously fallen 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.

In the east around 325, Shapur II regained the upper hand against the Kushano-Sasanian Kingdom and took control of large territories in areas now known as Afghanistan and Pakistan. Cultural expansion followed this victory, and Sasanian art penetrated Transoxiana, 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 retaking Singara and Amida. In response the Roman emperor Julian struck deep into Persian territory and defeated Shapur's forces at Ctesiphon. He failed to take the capital, however, and was killed while trying to retreat to Roman territory. His successor Jovian, trapped on the east bank of the Tigris, had to hand over all the provinces the Persians had ceded to Rome in 298, as well as Nisibis and Singara, to secure safe passage for his army out of Persia. Hostilities with the Roman Empire soon resumed in the Armeno-Sasanian War of 363–371, when Shapur II attempted to consolidate control over Armenia, which led to the subsequent intervention of Emperor Valens and the victory of joint Roman-Armenian forces at Bagavan in 371. According to contemporary historians, the Sassanids had to cede much of the southern Caucasus and northern Mesopotamia to the Romans and their Armenian allies, largely neutralizing the gains made by Shapur II in 363. Afterwards, a seven-year truce was negotiated, which ensured relative peace on the border until 378/379, shortly before Shapur II's death.

From around 370, towards the end of the reign of Shapur II, the Sasanians lost the control of Bactria to invaders from the north: first the Kidarites, then the Hephthalites and finally the Alchon Huns, who would follow up with an invasion of India. These invaders initially issued coins based on Sasanian designs.

The Sasanians established an empire roughly within the frontiers achieved by the Parthian Arsacids, with the capital at Ctesiphon in the Asoristan province. In administering this empire, Sassanid rulers took the title of shahanshah (King of Kings), becoming the central overlords and also assumed guardianship of the sacred fire, the symbol of the national religion. This symbol is explicit on Sasanian coins where the reigning monarch, with his crown and regalia of office, appears on the obverse, backed by the sacred fire, the symbol of the national religion, on the coin's reverse. Sassanid queens had the title of banbishnan banbishn (Queen of Queens).

On a smaller scale, the territory might also be ruled by a number of petty rulers from a noble family, known as shahrdar, overseen directly by the shahanshah. The districts of the provinces were ruled by a shahrab and a mowbed (chief priest). The mowbed dealt with estates and other legal matters. Sasanian rule was characterized by considerable centralization, ambitious urban planning, agricultural development, and technological improvements. Below the king, a powerful bureaucracy carried out much of the affairs of government; the head of the bureaucracy was the wuzurg framadar (vizier or prime minister). Within this bureaucracy the Zoroastrian priesthood was immensely powerful. Below the emperor, the most powerful men of the Sassanid state were his chief officials: the mowbedan mowbed, the head of the priestly class (magi); the spahbed, the commander-in-chief; the hutukhshbed, the head of traders and merchants' syndicate; and the minister of agriculture, the wastaryoshan-salar, who was also head of farmers.

Formally absolute monarchs, the Sasanian rulers usually considered the advice of their ministers. A 10th-century Muslim historian, al-Masudi, praised the "excellent administration of the Sasanian kings, their well-ordered policy, their care for their subjects, and the prosperity of their domains". In normal times, the monarchical office was hereditary, but might be transferred by the king to a younger son; in two instances the supreme power was held by queens. When no direct heir was available, the nobles and prelates chose a ruler, but their choice was restricted to members of the royal family.

The Sasanian nobility was a mixture of old Parthian clans, Persian aristocratic families, and noble families from subjected territories. Many new noble families had risen after the dissolution of the Parthian dynasty, while several of the once-dominant Seven Parthian clans remained of high importance. At the court of Ardashir I, the old Arsacid families of the House of Karen and the House of Suren, along with several other families, the Varazes and Andigans, held positions of great honor. Alongside these Iranian and non-Iranian noble families, the kings of Merv, Abarshahr, Kirman, Sakastan, Iberia, and Adiabene, who are mentioned as holding positions of honor amongst the nobles, appeared at the court of the shahanshah. Indeed, the extensive domains of the Surens, Karens, and Varazes, had become part of the original Sassanid state as semi-independent states. Thus, the noble families that attended at the court of the Sassanid empire continued to be ruling lines in their own right, although subordinate to the shahanshah.

In general, wuzurgan from Iranian families held the most powerful positions in the imperial administration, including governorships of border provinces (marzban). Most of these positions were patrimonial, and many were passed down through a single family for generations. The marzbans of greatest seniority were permitted a silver throne, while marzbans of the most strategic border provinces, such as the Caucasus province, were allowed a golden throne. In military campaigns, the regional marzbans could be regarded as field marshals, while lesser spahbeds could command a field army.

Culturally, the Sasanians implemented a system of social stratification. This system was supported by Zoroastrianism, which was established as the state religion. Other religions appear to have been largely tolerated, although this claim has been debated. Sassanid emperors consciously sought to resuscitate Persian traditions and to obliterate Greek cultural influence.

According to historian Scott McDonough and Kaveh Farrokh, a key principle of the Sasanian Empire's monarchy was to defend the Aryan settlers and culture of the realm. This included the integration and protection of the Parthians and other Iranic peoples. The Sasanians extended Aryan identity to Armenians who already had strong ties to the Iranic world, notably due to their admixture with the Parthians.

The active army of the Sasanian Empire originated from Ardashir I, the first shahanshah of the empire. Ardashir restored the Achaemenid military organizations, retained the Parthian cavalry model, and employed new types of armour and siege warfare techniques.

The relationship between priests and warriors was important, because the concept of Ērānshahr had been revived by the priests. Disagreements between the priests and the warriors led to fragmentation within the empire, which led to its downfall.

The Paygan formed the bulk of the Sasanian infantry, and were often recruited from the peasant population. Each unit was headed by an officer called a "Paygan-salar", which meant "commander of the infantry" and their main task was to guard the baggage train, serve as pages to the Asvaran (a higher rank), storm fortification walls, undertake entrenchment projects, and excavate mines.

Those serving in the infantry were fitted with shields and lances. To make the size of their army larger, the Sasanians added soldiers provided by the Medes and the Dailamites to their own. The Medes provided the Sasanian army with high-quality javelin throwers, slingers, and heavy infantry. Iranian infantry are described by Ammianus Marcellinus as "armed like gladiators" and "obey orders like so many horse-boys". The Dailamite people also served as infantry and were Iranian people who lived mainly within Gilan, Iranian Azerbaijan and Mazandaran. They are reported as having fought with weapons such as daggers, swords, and javelins and reputed to have been recognized by Romans for their skills and hardiness in close-quarter combat. One account of Dailamites recounted their participation in an invasion of Yemen where 800 of them were led by the Dailamite officer Vahriz. Vahriz would eventually defeat the Arab forces in Yemen and its capital Sana'a making it a Sasanian vassal until the invasion of Persia by Arabs.

The Sasanian navy was an important constituent of the Sasanian military from the time that Ardashir I conquered the Arab side of the Persian Gulf. Because controlling the Persian Gulf was an economic necessity, the Sasanian navy worked to keep it safe from piracy, prevent Roman encroachment, and keep the Arab tribes from getting hostile. However, it is believed by many historians that the naval force could not have been a strong one, as the men serving in the navy were those who were confined in prisons. The leader of the navy bore the title of nāvbed.

The cavalry used during the Sasanian Empire were two types of heavy cavalry units: Clibanarii and Cataphracts. The first cavalry force, composed of elite noblemen trained since youth for military service, was supported by light cavalry, infantry and archers. Mercenaries and tribal people of the empire, including the Turks, Kushans, Sarmatians, Khazars, Georgians, and Armenians were included in these first cavalry units. The second cavalry involved the use of the war elephants. In fact, it was their specialty to deploy elephants as cavalry support.

Unlike the Parthians, the Sasanians developed advanced siege engines. The development of siege weapons was a useful weapon during conflicts with Rome, in which success hinged upon the ability to seize cities and other fortified points; conversely, the Sassanids also developed a number of techniques for defending their own cities from attack. The Sasanian army was much like the preceding Parthian army, although some of the Sassanid's heavy cavalry were equipped with lances, while Parthian armies were heavily equipped with bows. The Roman historian Ammianus Marcellinus's description of Shapur II's clibanarii cavalry manifestly shows how heavily equipped it was, and how only a portion were spear equipped:

All the companies were clad in iron, and all parts of their bodies were covered with thick plates, so fitted that the stiff-joints conformed with those of their limbs; and the forms of human faces were so skillfully fitted to their heads, that since their entire body was covered with metal, arrows that fell upon them could lodge only where they could see a little through tiny openings opposite the pupil of the eye, or where through the tip of their nose they were able to get a little breath. Of these, some who were armed with pikes, stood so motionless that you would have thought them held fast by clamps of bronze.

Horsemen in the Sasanian cavalry lacked a stirrup. Instead, they used a war saddle which had a cantle at the back and two guard clamps which curved across the top of the rider's thighs. This allowed the horsemen to stay in the saddle at all times during the battle, especially during violent encounters.

The Byzantine emperor Maurikios also emphasizes in his Strategikon that many of the Sassanid heavy cavalry did not carry spears, relying on their bows as their primary weapons. Conversely the Taq-e Bostan reliefs and Al-Tabari's famed list of equipment required for dihqan knights included the lance.

The amount of money involved in maintaining a warrior of the Asawaran (Azatan) knightly caste required a small estate, and the Asawaran (Azatan) knightly caste received that from the throne, and in return, were the throne's most notable defenders in time of war.

The Sasanians, like the Parthians, were in constant hostilities with the Roman Empire. The Sasanians, who succeeded the Parthians, were recognized as one of the leading world powers alongside its neighboring rival the Byzantine Empire, or Eastern Roman Empire, for a period of more than 400 years. Following the division of the Roman Empire in 395, the Byzantine Empire, with its capital at Constantinople, continued as Persia's principal western enemy, and main enemy in general. Hostilities between the two empires became more frequent. The Sasanians, similar to the Roman Empire, were in a constant state of conflict with neighboring kingdoms and nomadic hordes. Although the threat of nomadic incursions could never be fully resolved, the Sasanians generally dealt much more successfully with these matters than did the Romans, due to their policy of making coordinated campaigns against threatening nomads.

The last of the many and frequent wars with the Byzantines, the climactic Byzantine–Sasanian War of 602–628, which included the siege of the Byzantine capital Constantinople, ended with both rivaling sides having drastically exhausted their human and material resources. Furthermore, social conflict within the Empire had considerably weakened it further. 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 forces swiftly conquered the entire Sasanian Empire and in the Byzantine–Arab Wars deprived the Byzantine Empire of its territories in the Levant, the Caucasus, Egypt, and North Africa. Over the following centuries, half the Byzantine Empire and the entire Sasanian Empire came under Muslim rule.

In general, over the span of the centuries, in the west, Sasanian territory abutted that of the large and stable Roman state, but to the east, its nearest neighbors were the Kushan Empire and nomadic tribes such as the White Huns. The construction of fortifications such as Tus citadel or the city of Nishapur, which later became a center of learning and trade, also assisted in defending the eastern provinces from attack.

In south and central Arabia, Bedouin Arab tribes occasionally raided the Sasanian Empire. The Kingdom of Al-Hirah, a Sasanian vassal kingdom, was established to form a buffer zone between the empire's heartland and the Bedouin tribes. The dissolution of the Kingdom of Al-Hirah by Khosrow II in 602 contributed greatly to decisive Sasanian defeats suffered against Bedouin Arabs later in the century. These defeats resulted in a sudden takeover of the Sasanian Empire by Bedouin tribes under the Islamic banner.

In the north, Khazars and the Western Turkic Khaganate frequently assaulted the northern provinces of the empire. They plundered Media in 634. Shortly thereafter, the Persian army defeated them and drove them out. The Sasanians built numerous fortifications in the Caucasus region to halt these attacks, such as the imposing fortifications built in Derbent (Dagestan, North Caucasus, now a part of Russia) that to a large extent, have remained intact up to this day.

On the eastern side of the Caspian Sea, the Sasanians erected the Great Wall of Gorgan, a 200 km-long defensive structure probably aimed to protect the empire from northern peoples, such as the White Huns.

In 522, before Khosrow's reign, a group of Monophysite Axumites led an attack on the dominant Himyarites of southern Arabia. The local Arab leader was able to resist the attack but appealed to the Sasanians for aid, while the Axumites subsequently turned towards the Byzantines for help. The Axumites sent another force across the Red Sea and this time successfully killed the Arab leader and replaced him with an Axumite man to be king of the region.

In 531, Emperor Justinian suggested that the Axumites of Yemen should cut out the Persians from Indian trade by maritime trade with the Indians. The Ethiopians never met this request because an Axumite general named Abraha took control of the Yemenite throne and created an independent nation. After Abraha's death one of his sons, Ma'd-Karib, went into exile while his half-brother took the throne. After being denied by Justinian, Ma'd-Karib sought help from Khosrow, who sent a small fleet and army under commander Vahriz to depose the new king of Yemen. After capturing the capital city San'a'l, Ma'd-Karib's son, Saif, was put on the throne.

Justinian was ultimately responsible for Sasanian maritime presence in Yemen. By not providing the Yemenite Arabs support, Khosrow was able to help Ma'd-Karib and subsequently established Yemen as a principality of the Sassanian Empire.

Like their predecessors the Parthians, the Sasanian Empire actively sought foreign relations with China, and ambassadors from Persia frequently travelled to China. Chinese documents mention sixteen Sassanid embassies to China from 455 to 555. Commercially, land and sea trade with China was important to both the Sasanians and the Chinese. Large numbers of Sasanian coins have been found in southern China, confirming the existence of maritime trade.

On different occasions, Sasanian kings sent their most talented Persian musicians and dancers to the Chinese imperial court at Luoyang during the Jin and Northern Wei dynasties, and to Chang'an during the Sui and Tang dynasties. Both empires benefited from trade along the Silk Road and shared a common interest in preserving and protecting that trade. They cooperated in guarding the trade routes through central Asia, and both built outposts in border areas to keep caravans safe from nomadic tribes and bandits.

Politically, there is evidence that on several occasions the Sasanians and the Chinese formed alliances to counter their common enemy, the Hephthalites. Upon the rise of the nomadic Göktürks in Inner Asia, there seems to have been what looks like an alliance between China and the Sasanians to check the Turkic advances. Documents from Mt. Mogh report the presence of a Chinese general in the service of the king of Sogdiana at the time of the Arab invasions.

Following the invasion of Iran by Muslim Arabs, Peroz III, son of Yazdegerd III, escaped along with a few Persian nobles and took refuge in the Chinese imperial court. Both Peroz and his son Narsieh (Chinese neh-shie) were given high titles at the Chinese court. In 661, Peroz III was appointed Governor of Persia. On at least two occasions, the last possibly in 670, Chinese troops were sent with Peroz in order to restore him to the Sasanian throne. Narsieh later attained the position of a commander of the Chinese imperial guards, and his descendants lived in China as respected princes. Sasanian refugees who fled the Arab conquests settled in China, during the reign of the Chinese emperor Gaozong of Tang.

Following the conquest of Iran and neighboring regions, Shapur I extended his authority northwest of the Indian subcontinent. The previously autonomous Kushans were obliged to accept his suzerainty. These were the western Kushans which controlled Afghanistan while the eastern Kushans were active in India. Although the Kushan empire declined at the end of the 3rd century, to be replaced by the Indian Gupta Empire in the 4th century, it is clear that the Sasanians remained relevant in India's northwest throughout this period.

Persia and northwestern India, the latter that made up formerly part of the Kushans, engaged in cultural as well as political exchange during this period, as certain Sasanian practices spread into the Kushan territories. In particular, the Kushans were influenced by the Sasanian conception of kingship, which spread through the trade of Sasanian silverware and textiles depicting emperors hunting or dispensing justice.

This cultural interchange did not, however, spread Sasanian religious practices or attitudes to the Kushans. Lower-level cultural interchanges also took place between India and Persia during this period. For example, Persians imported the early form of chess, the chaturanga (Middle Persian: chatrang) from India. In exchange, Persians introduced backgammon (Nēw-Ardašēr) to India.

During Khosrow I's reign, many books were brought from India and translated into Middle Persian. Some of these later found their way into the literature of the Islamic world and Arabic literature. A notable example of this was the translation of the Indian Panchatantra by one of Khosrow's ministers, Borzuya. This translation, known as the Kalīlag ud Dimnag, later made its way into the Arabic literature and Europe. The details of Borzuya's legendary journey to India and his daring acquisition of the Panchatantra are written in full detail in Ferdowsi's Shahnameh, which says:

In Indian books, Borzuya read that on a mountain in that land there grows a plant which when sprinkled over the dead revives them. Borzuya asked Khosrau I for permission to travel to India to obtain the plant. After a fruitless search, he was led to an ascetic who revealed the secret of the plant to him: The "plant" was word, the "mountain" learning, and the "dead" the ignorant. He told Borzuya of a book, the remedy of ignorance, called the Kalila, which was kept in a treasure chamber. The king of India gave Borzuya permission to read the Kalila, provided that he did not make a copy of it. Borzuya accepted the condition but each day memorized a chapter of the book. When he returned to his room he would record what he had memorized that day, thus creating a copy of the book, which he sent to Iran. In Iran, Bozorgmehr translated the book into Pahlavi and, at Borzuya's request, named the first chapter after him.

In contrast to Parthian society, the Sasanians renewed emphasis on a charismatic and centralized government. In Sasanian theory, the ideal society could maintain stability and justice, and the necessary instrument for this was a strong monarch. Thus, the Sasanians aimed to be an urban empire, at which they were quite successful. During the late Sasanian period, Mesopotamia had the largest population density in the medieval world. This can be credited to, among other things, the Sasanians founding and re-founding a number of cities, which is talked about in the surviving Middle Persian text Šahrestānīhā ī Ērānšahr (the provincial capitals of Iran). Ardashir I himself built and re-built many cities, which he named after himself, such as Veh-Ardashir in Asoristan, Ardashir-Khwarrah in Pars and Vahman-Ardashir in Meshan. During the Sasanian period, many cities with the name "Iran-khwarrah" were established. This was because Sasanians wanted to revive Avesta ideology.

Many of these cities, both new and old, were populated not only by native ethnic groups, such as the Iranians or Syriacs, but also by the deported Roman prisoners of war, such as Goths, Slavs, Latins, and others. Many of these prisoners were experienced workers, who were used to build things such as cities, bridges, and dams. This allowed the Sasanians to become familiar with Roman technology. The impact these foreigners made on the economy was significant, as many of them were Christians, and the spread of the religion accelerated throughout the empire.

Unlike the amount of information about the settled people of the Sasanian Empire, there is little about the nomadic/unsettled ones. It is known that they were called "Kurds" by the Sasanians, and that they regularly served the Sasanian military, particularly the Dailamite and Gilani nomads. This way of handling the nomads continued into the Islamic period, where the service of the Dailamites and Gilanis continued unabated.

The head of the Sasanian Empire was the shahanshah (king of kings), also simply known as the shah (king). His health and welfare was of high importance—accordingly, the phrase "May you be immortal" was used to reply to him. The Sasanian coins which appeared from the 6th-century and afterwards depict a moon and sun, which, in the words of the Iranian historian Touraj Daryaee, "suggest that the king was at the center of the world and the sun and moon revolved around him." In effect he was the "king of the four corners of the world", which was an old Mesopotamian idea. The king saw all other rulers, such as the Romans, Turks, and Chinese, as being beneath him. The king wore colorful clothes, makeup, a heavy crown, while his beard was decorated with gold. The early Sasanian kings considered themselves of divine descent; they called themselves "bay" (divine).

When the king went out in public, he was hidden behind a curtain, and had some of his men in front of him, whose duty was to keep the masses away from him and to clear the way. When one came to the king, one was expected to prostrate oneself before him, also known as proskynesis. The king's guards were known as the pushtigban. On other occasions, the king was protected by a discrete group of palace guards, known as the darigan. Both of these groups were enlisted from royal families of the Sasanian Empire, and were under the command of the hazarbed, who was in charge of the king's safety, controlled the entrance of the kings palace, presented visitors to the king, and was allowed military commands or used as a negotiator. The hazarbed was also allowed in some cases to serve as the royal executioner. During Nowruz (Iranian new year) and Mihragan (Mihr's day), the king would hold a speech.

Sasanian society was immensely complex, with separate systems of social organization governing numerous different groups within the empire. Historians believe society comprised four social classes:

Asronan (priests)

Arteshtaran (warriors)

Wastaryoshan (commoners)

Hutukhshan (artisans)

At the center of the Sasanian caste system the shahanshah ruled over all the nobles. The royal princes, petty rulers, great landlords and priests, together constituted a privileged stratum, and were identified as wuzurgan, or grandees. This social system appears to have been fairly rigid.

This social system was strictly stratified with virtually no social mobility. State and religious laws explicitly forbade intermarriage and movement between classes. The lower classes (Wastaryoshan and Hutukhshan) bore the overwhelming majority of the state's tax burden. Furthermore, formal education was legally monopolized by the nobility and priesthood, while commoners were intentionally barred from education to ensure they remained in their inherited caste-ordained professions.

The Sasanian caste system outlived the empire, continuing in the early Islamic period. The Sasanian caste system was directly based on Zoroastrian doctrine.

In general, mass slavery was never practiced by the Iranians, and in many cases the situation and lives of semi-slaves (prisoners of war) were, in fact, better than those of the commoner. In Persia, the term "slave" was also used for debtors who had to use some of their time to serve in a fire-temple.

Some of the laws governing the ownership and treatment of slaves can be found in the legal compilation called the Mādayān ī Hazār Dādestān, a collection of rulings by Sasanian judges. Principles that can be inferred from the laws include:

Sources of slaves were both foreign (e.g., non-Zoroastrians captives from warfare or raiding or slaves imported from outside the Empire by traders) or domestic (e.g., hereditary slaves, children sold into slavery by their fathers, or criminals enslaved as punishment). Some cases suggest that a criminal's family might also be condemned to servitude. At the time of the manuscript's composition, Iranian slavery was hereditary on the mother's side (so that a child of a free man and a slave woman would be a slave), although the author reports that in earlier Persian history it may have been the opposite, being inherited from the father's side.

Slave owners had the right to the slaves' income.

While slaves were formally chattel (property) and were liable to the same legal treatment as nonhuman property (for example, they could be sold at will, rented, owned jointly, inherited, given as security for a loan, etc.), Sasanian courts did not treat them completely as objects; for example, slaves were allowed to testify in court in cases concerning them, rather than only permitted to be represented by their owners.

Slaves were often given to the Zoroastrian fire temples as a pious offering, in which case they and their descendants would become temple-slaves.

Excessive cruelty towards slaves could result in the owners' being brought to court; a court case involving a slave whose owner tried to drown him in the Tigris River is recorded, though without stating the outcome of the case.

If a non-Zoroastrian slave, such as a Christian slave, converted to Zoroastrianism, he or she could pay their price and attain freedom; i.e., as long as the owner was compensated, manumission was required.

Owners could also voluntarily manumit their slaves, in which case the former slave became a subject of the Sasanian King of Kings and could not lawfully be re-enslaved later. Manumissions were recorded, which suggests that a freedman who was challenged would be able to document their free status.

Uniquely in comparison to Western slave systems, Sasanian slavery recognized partial manumission (relevant in the case of a jointly owned slave, only some of whose owners were willing to manumit). In case of a slave who was, e.g., one-half manumitted, the slave would serve in alternating years.

To free a slave (irrespective of their faith) was considered a good deed. Slaves had some rights including keeping gifts from the owner and at least three days of rest in the month.

The most common slaves in the Sasanian Empire were the household servants, who worked in private estates and at the fire-temples. Usage of a woman slave in a home was common, and her master had outright control over her and could even produce children with her if he wanted to. Slaves also received wages and were able to have their own families whether they were female or male. Harming a slave was considered a crime, and not even the king himself was allowed to do it.

The master of a slave was allowed to free the person whenever he wanted to. A slave could also be freed at the death of his/her master.

There was a major school, called the Grand School, in the capital. In the beginning, only 50 students were allowed to study at the Grand School. In less than 100 years, enrollment at the Grand School was over 30,000 students.

On a lower level, Sasanian society was divided into Azatan (freemen). The Azatan formed a large low-aristocracy of low-level administrators, mostly living on small estates. The Azatan provided the cavalry backbone of the Sasanian army.

The Sasanian kings were patrons of letters and philosophy. Khosrow I had the works of Plato and Aristotle, translated into Pahlavi, taught at Gundishapur, and read them himself. During his reign, many historical annals were compiled, of which the sole survivor is the Karnamak-i Artaxshir-i Papakan (Deeds of Ardashir), a mixture of history and romance that served as the basis of the Iranian national epic, the Shahnameh. When Justinian I closed the schools of Athens, seven of their professors went to Persia and found refuge at Khosrow's court. In his treaty of 533 with Justinian, the Sasanian king stipulated that the Greek sages should be allowed to return and be free from persecution.

Under Khosrow I, the Academy of Gundishapur, which had been founded in the 5th century, became "the greatest intellectual center of the time", drawing students and teachers from every quarter of the known world. Nestorian Christians were received there, and brought Syriac translations of Greek works in medicine and philosophy. The medical lore of India, Persia, Syria, and Greece mingled there to produce a flourishing school of therapy.

The Sasanian period saw an open exchange of ideas with other people, in particular with India and Byzantium. From India, works on medicine, astronomy, mirrors for princes and fables such as the panchatantra were imported and translated. Indian works on astrology were especially prized and much effort was dedicated to their translation. Chess was also imported from India, where it was adopted and underwent further development. From Byzantium came musical instruments, scientific, medical, and philosophical works. The decision of emperor Justinian to close down the neo-platonic school in Athens caused many philosophers to travel to Persia and seek work at the academy of Gondishapur.

Artistically, the Sasanian period witnessed some of the highest achievements of Iranian civilization. Much of what would later become known as Islamic culture, including architecture and writing, was originally drawn from Persian culture. At its peak, the Sasanian Empire stretched from western Anatolia to northwest India (today Pakistan), but its influence was felt far beyond these political boundaries. Sasanian motifs found their way into the art of Central Asia and China, the Byzantine Empire, and even Merovingian France. Islamic art however, was the true heir to Sasanian art, whose concepts it was to assimilate while at the same time instilling fresh life and renewed vigor into it. According to Will Durant:

Sasanian art exported its forms and motifs eastward into India, Turkestan and China, westward into Syria, Asia Minor, Constantinople, the Balkans, Egypt and Spain. Probably its influence helped to change the emphasis in Greek art from classic representation to Byzantine ornament, and in Latin Christian art from wooden ceilings to brick or stone vaults and domes and buttressed walls.

Sasanian carvings at Taq-e Bostan and Naqsh-e Rustam were colored; so were many features of the palaces; but only traces of such painting remain. The literature, however, makes it clear that the art of painting flourished in Sasanian times. Painting, sculpture, pottery, and other forms of decoration shared their designs with Sasanian textile art. Silks, embroideries, brocades, damasks, tapestries, chair covers, canopies, tents, and rugs were woven with patience and masterly skill, and were dyed in warm tints of yellow, blue and green. Great colorful carpets had been an appendage of wealth in the East since Assyrian days. The two dozen Sasanian textiles that have survived are among the most highly valued fabrics in existence. Even in their own day, Sasanian textiles were admired and imitated from Egypt to the Far East; and during the Middle Ages, they were favored for clothing the relics of Christian saints.

Studies on Sasanian remains show over 100 types of crowns being worn by Sasanian kings. The various Sasanian crowns demonstrate the cultural, economic, social and historical situation in each period. The crowns also show the character traits of each king in this era. Different symbols and signs on the crowns—the moon, stars, eagle and palm, each illustrate the wearer's religious faith and beliefs.

The Sasanian dynasty, like the Achaemenid, originated in the province of Pars. The Sasanians saw themselves as successors of the Achaemenids, after the Hellenistic and Parthian interlude, and believed that it was their destiny to restore the greatness of Persia.

When reviving the glories of the Achaemenid past, the Sasanians went beyond imitation. The art of this period reveals an astonishing virility, in certain respects anticipating key features of Islamic art. Sasanian art combined elements of traditional Persian art with Hellenistic elements and influences. The conquest of Persia by Alexander the Great helped introduce Hellenistic art to the East. Though the East accepted the outward form of this art, it never really assimilated its spirit. By the Parthian period, Hellenistic art was being interpreted freely by the peoples of the Near East, and during the Sasanian period, there was reaction against it. Sasanian art revived forms and traditions native to Persia, and in the Islamic period, these reached the shores of the Mediterranean. According to Fergusson:

"With the accession of the [Sasanians], Persia regained much of that power and stability to which she had been so long a stranger ... The improvement in the fine arts at home indicates returning prosperity, and a degree of security unknown since the fall of the Achaemenidae."

Surviving palaces illustrate the splendor in which the Sasanian monarchs lived. Examples include palaces at Firuzabad and Bishapur in pars, and the capital city of Ctesiphon in the Asoristan province (present-day Iraq). In addition to local traditions, Parthian architecture influenced Sasanian architectural characteristics. All are characterized by the barrel-vaulted iwans introduced in the Parthian period. During the Sasanian period, these reached massive proportions, particularly at Ctesiphon. There, the arch of the great vaulted hall, attributed to the reign of Shapur I (241–272), has a span of more than 80 feet (24 m) and reaches a height of 118 feet (36 m). This magnificent structure fascinated architects in the centuries that followed and has been considered one of the most important examples of Persian architecture. Many of the palaces contain an inner audience hall consisting, as at Firuzabad, of a chamber surmounted by a dome. The Persians solved the problem of constructing a circular dome on a square building by employing squinches, or arches built across each corner of the square, thereby converting it into an octagon on which it is simple to place the dome. The dome chamber in the palace of Firuzabad is the earliest surviving example of the use of the squinch, suggesting that this architectural technique was probably invented in Persia.

Among the unique characteristics of Sasanian architecture was its distinctive use of space. The Sasanian architect conceived his building in terms of masses and surfaces; hence the use of massive walls of brick decorated with molded or carved stucco. Stucco wall decorations appear at Bishapur, but better examples are preserved at Chal Tarkhan near Rey, which date to the late Sasanian or early Islamic period, and from Ctesiphon and Kish in Mesopotamia. The panels show animal figures set in roundels, human busts, and geometric and floral motifs.