The Muslim conquest of Persia occurred from 633 to 654 AD when the Arab Muslims of the Rashidun Caliphate invaded and conquered the powerful Persian Zoroastrian Sassanid Empire. The Sassanids had been exhausted by a devastating war with the Byzantines earlier in the 7th century, as well as by a series of civil wars, and, while they repulsed the first Arab invasion in 633, the second invasion in 636 resulted in a crushing Persian defeat at the Battle of al-Qadisiyyah, which cost Persia control over Mesopotamia and all other lands west of Iran. In 642, Caliph Umar ordered a full-scale invasion across the Zagros Mountains and into Persia proper, overseeing a series of well-coordinated, multi-pronged attacks. Persian-ruled Armenia fell to the Arabs from 643 to 644. By 651, most of Persia's urban centers, with the exception of Tabaristan near the Caspian Sea and Transoxiana in Central Asia, had fallen into Arab hands. Several Persian rebellions broke out across the former empire, killing Arab governors and attacking their garrisons. Eventually, the Rashiduns sent in military reinforcements to crush the insurgencies and impose Islamic control. Azerbaijan was conquered in 651, and Ahnaf ibn Qais began the conquest of Khorasan (Central Asia) that same year. Yazdegerd fled from his capital of Merv and relocated to Balkh, and his army was defeated at the Battle of Oxus River in Turkmenistan in 651, forcing Yazdegerd to flee to China. He was later murdered in a robbery near Merv, putting an end to organized Persian resistance. The Sassanid court went into exile at Chang'an in Tang China, where they attempted to organize Sino-Persian reconquest attempts; none of these expeditions reached Persia itself, and they came to an end in 728 with the death of the last Sassanid pretender and with Tang China's increasing instability caused by the An Lushan Rebellion. Persia was gradually Islamized over the next few centuries, but it was never Arabized, as the Persians retained their language and culture. While the Arabs had occasionally burnt Zoroastrian scriptures and executed Persian priests in retaliation for Persian revolts, thousands of Zoroastrian Persians remained unconverted into the 21st century. It would not be until the late Middle Ages that Sunni Islam became the dominant religion in Persia, and it would remain so until the rise of the Shia Safavids in the 16th century.
Background[]
Birth of Islam[]
As Sassanid Persia recovered from an exhausting war with the Byzantine Empire in the 620s, the Arabian Peninsula underwent upheaval. Its population was divided between Arab pagans, Christians, Jews, and Zoroastrians; the Sassanids controlled the province of Mazun and eastern Yemen, while the deserts of central and northern Arabia were ruled by the Bedouin Arabs. The Arab city-state of Mecca, governed by the Quraysh tribe, traded spice with the Romans, Persians, and Axum. The merchant Muhammad was influenced by the various faiths he met while on his travels, and, from 610 onwards, he began to share visions which he had purportedly received from the Archangel Gabriel, spreading the new faith of Islam. The Quraysh feared that the "Muslims" would subvert their power, leading to a persecution in 614 AD which forced the Muslims to emigrate to Medina in 622 AD. By 629, the Muslims of Medina had defeated and conquered the Quraysh of Medina. He then sent envoys to the neighboring states, urging their leaders to convert to Islam. Shah Khusrau II of Persia insulted the Muslim envoy, while the one sent to Emperor Heraclius was killed in Ghassanid territory. Muhammad retaliated by sending an army to invade Ghassanid territory, only for this army to be defeated at the Battle of Mu'tah in September 629. Muhammad decided to lead a 30,000-strong punitive expedition, taking the city of Tabuk from the Byzantines. By 631, most of the Arabian Peninsula was under Muslim control. Muhammad died a year later, and Abu Bakr succeeded him as leader of the Muslims with the title of "Caliph", becoming the first ruler of the Rashidun Caliphate.
Crisis in Persia[]
The political situation in 632
In the meantime, Shah Kavadh II began killing his brothers in order to secure his throne, leading to deepening disagreements between the Persian and Parthian nobles. Kavadh died of plague in September, and his 8-year-old son Ardashir III came to be controlled by the vizier Mah-Adhur Gushnasp. This deeply concerned the Persian party, which allied with Khusrau's general Shahbaraz; Shahbaraz took the capital of Ctesiphon in April of 630 AD, killing Ardashir and Mah-Adhur and becoming the Shah. The Sassanid realm fell into civil war, and the governors of Yemen and Mazun went on to declare independence from Ctesiphon, making them easy conquests for the Caliphate. Just 40 days later, Shahbaraz was killed, and the Parthian leader Farrukh Hormizd raised Khusrau's daughter Purandokht to the throne. She was overthrown by Shahbaraz's son Shapur shortly after, and Farrukh decided to have Shapur marry Khusrau's other daughter Azarmidokht to make peace between the factions. Azarmidokht refused, so farrukh Hormizd usurped the throne for himself in late 630; Azarmidokht's supporters proceeded to kill him in 631 and restore Azarmidokht to power. Azarmidokht was then challenged by Farrukh's son Rostam Farrokhzad, who defeated Azarmidokht's armies along the route to Ctesiphon, which he then took, reinstalling Purandokht in power. The leader of the Persian clique, Piruz Khosrow, decided to end the hostilities, but, after Rostam left the capital for the frontier, Piruz killed Purandokht in June 632. Rostam then marched for the capital again, but the two armies mutinied and forced their generals to make peace, leading to Khosrau's 8-year-old grandson Yazdegerd III becoming Shah. The Sassanid realm was now critically endangered, as the Parthian clique controlled the northeastern provinces, and Turkic raiders attacked from the Caucasus and Central Asia. In addition, the Arab tribal leader al-Muthanna ibn Haritha launched several raids on southern Mesopotamia, and, in early 633, Muthanna - who had since converted to Islam - informed the Rashidun Caliph Abu Bakr of the weakness of the Sassanid border. The Caliph decided to send Khalid ibn al-Walid to invade Iraq, and Khalid assembled an army of 18,000 at his base at Yamama before setting out for Iraq in late March 633.
War[]
First Arab invasion[]
Khalid ibn al-Walid's army advancing
Khalid sent a messenger to the Governor of Dast Meisan, Hormozd, demanding his surrender. Hormozd refused, but sent a letter to the capital, asking Yazdegerd for reinforcements. As Hormozd gathered his 20,000 troops after leaving the provincial capital of Uballa, Khalid moved his troops through the desert and threatened Hufair, forcing Hormozd to confront him to the south of Kazima. In the Battle of Chains, Khalid and his army destroyed the outmaneuvered and tired-out Sassanid army. The Persian general Karinz had concurrently been sent south with a reinforcement army of 15-25,000 troops from the capital region, crossing the Tigris and moving towards Uballa. He then found the remaining 10,000 men from Hormozd's army, who had told him of their defeat. Meanwhile, Muthanna led an advance guard to scout the Persian positions, while Khalid recruited men from the Arab tribes in the area of Kazima and Hufair. Karinz decided to abandon Uballa, worried that Muthanna could attack his flanks, and he withdrew to al-Hirah. Khalid then sent a small force to take Uballa before facing a new army which was moving to the south, uniting with Muthanna's army before facing off with the Sassanids at the Battle of River. There, all of the Persian commanders were killed in duels at the start of the battle, and their leaderless and disorganized army was destroyed in separate halves.
The situation in April 633
Khalid did not immediately invade Iraq, however, staying behind to organize an administration to collect taxes in the region, and refusing to overextend his supply lines and advance into territory with no Arab tribes. Khalid had the province's inhabitants pay the jizya tax, and he sent local scouts to search for new Sassanid armies. Hearing of the defeat via Persia's advanced postal system, Yazdegerd summoned troops from the northern and eastern parts of the empire to march towards the capital of Ctesiphon, and the first Persian army, led by Andarzaghar, was sent towards Walaja. There, he joined the remnants of Karinz's army, bringing his army to a strength of between 25,000 and 30,000 troops. Bahman Jadhuyih commanded a 20,000-strong reinforcement army which guarded al-Hira halfway from a base between Uballa and Walaja. Khalid left a minor garrison at Uballa and decided to defeat Andarzaghar before alerting Bahman, reinforcing his men from the supportive Arab tribes as he marched; the Arabs appreciated the lower tax rate. Khalid met Andarzaghar's army at the Battle of Walaja, where he annihilated the 25,000-strong Persian army. Khalid's army was too tired to pursue the Persian survivors, most of whom were Arab Christians. They gathered other Arab Christian tribes from the northwest and alerted the Shah in Ctesiphon, and the Arab Christian tribesmen joined forces with the Persian general Jaban, who replaced Bahman, who returned to Ctesiphon. Khalid moved his troops towards Ullais, where he annihilated the 70,000-strong Persian and Arab army. Khalid then approached Hira, the initial goal of his campaign, and he captured the town after convincing its defenders to settle for paying the jizya tax.
The raids on the Iraqi border
Over the next few months, the Arabs halted their advance as they set up a new administration in the region to collect taxes, and raiding parties were sent to burn Ain al-Tamr, Zumeil, Saniyy, and Muzayyah and bring back loot and information on enemy movement. Khalid's scouts did not receive much resistance, but his scouts warned him of large garrisons at Anbar and Ain al-Tamr. In late June, Khalid left half of his army to guard Hira as he brought 10,000 troops to attack Anbar, which was further away from Ain al-Tamr, giving him the element of surprise. al-Anbar surrendered after a quick battle, and Ain al-Tamr followed in July. Khalid then set up an administration in the newly-conquered region and sent most of his non-garrisoned troops to finish off the remnants of the Arab rebels at Dumat al-Jandal in Arabia. This inactivity gave some time to the Sassanids, who recruited and concentrated five armies in the region.
The situation before the Battle of Muzayya
At the end of September, Khalid ibn al-Walid returned to Iraq, and, throughout October, the Sassanids suffered several minor defeats at the hands of the Muslims. The Sassanid armies withdrew towards Muzayya, giving Khalid an open route to the Persian capital of Ctesiphon. However, he resolved to destroy the Persian armies at Muzayya first. The three Arab armies bypassed Saniyy and Zumeil and ambushed the Persian army as its slept, wiping out half of its strength. He then destroyed the Christian Arab armies at Saniyy and Zumeil, and an appeal against Khalid from the family of some recent Muslim converts slain while fighting for the Sassanids would be rejected by Caliph Abu Bakr, only to later be re-examined by the Caliph Umar and play a role in Khalid's downfall. By now, the region between Muzayya and Hira fell under the control of the caliphate, and the Persians living in the cities were often taken captive and enslaved, while the local Arabs were granted autonomy and freedom of worship in exchange for paying the jizya tax. Khalid then sent raiding parties across the Euphrates as he made new plans. Attacking Ctesiphon would overextend his supply lines, so his only option was to attack the Sassanid base at Firaz on the border of the Sassanid and Byzantine empires. The ensuing Battle of Firaz saw Khalid win another masterful victory over a combined Persian-Byzantine army, but, before he could push deeper into Persian territory, he received a letter from Abu Bakr which ordered him to move into Syria to battle the Romans.
Persian counterattack[]
The Persian counterattack in 634
By late 634, al-Muthanna ibn Haritha had been given command of the Arab army in Mesopotamia, and his 9,000-strong army raided central Mesopotamia to keep the superior Sassanid forces at bay. The Sassanids had a difficult time containing the raids, one of which reached Babylon. The Sassanid vizier Rostam Farrokhzad took command of an army in Ctesiphon and marched south, supported by the Sassanid generals Bahman Jaduya, Jaban, and Narsi and the Armenian prince Jalinus. Even before the multi-pronged counterattack began, Muthanna called for reinforcements, and, by August, this messenger was in Medina, just in time for Umar's ascension. Umar sent Abu Ubayd al-Thaqafi to command in Iraq, giving him 6,000 troops to reinforce Muthanna. When Jaban got close to al-Hira in September, Muthanna withdrew to Khaffan, where he was joined by Abu Ubayd in early October; the Caliphate's army now totalled 15,000, facing Jaban's similarly sized army and engaging him at the Battle of Namaraq. The Persians suffered a minor defeat, and Abu Ubayd then decided to fight the approaching Sassanid armies in detail. He won another minor victory at the Battle of Kaskar, but he was forced to retreat back across the Euphrates to avoid having his escape route cut off. In late October, the Persians tried to ford the river near Kufa, and the 20,000-strong Persian army faced off against Abu Ubayd's 15,000 troops. The Persian elephants created disarray among the Arab lines, and most of the Arab leaders - including Abu Ubayd - were killed, while Muthanna was heavily wounded while fighting off the pursuing Persians. The last months of the year saw Bahram return to Ctesiphon to put down another revolt against Rostam and fight off Turkic raiders, while Muthanna defeated a new Persian army under Mihran bin Badhan at the Battle of Buwaib.
Second invasion[]
In the aftermath of the Battle of the Bridge, Sassanid forces made no move to capitalize on their victory, as they were preoccupied with other matters. Umar then released another army from the previously untapped tribes who had been conquered during the Ridda Wars, and they were supplemented by additional contingents posted by Umar. Umar appointed the impartial and well-respected general Sa'd ibn Abi Waqqas to command the army, as he had been the seventh person to embrace Islam and was seen as beyond reproach. Many more warriors joined Sa'd's invasion force in May 636 as he marched on the Euphrates, and he assembled the most formidable army that the Persians had yet faced. The best Persian general Rostam Farrokhzad initially hoped to defeat the Arabs in a series of small battles, but this decision was unpopular with the nobles and citizens alike. Rostam was pressured to lead a massive imperial force to confront the Arabs at the Battle of al-Qadisiyyah, where they took advantage of a sandstorm to turn the tide against the Persians and rout the Persian army after a hard-fought battle. Rostam was killed and half of his army was destroyed, and the Arab victory cleared the way for the Arabs to conquer Mesopotamia.
Fall of Persia[]
The Battle of Nahavand
The defeat at Qadisiyyah broke the back of the Sassanid army, and, a few months later, the Persian capital of Ctesiphon fell. The remainder of those loyal to the Sassanid king withdrew beyond the Zagros Mountains into Iran. Yazdegerd ordered continuous cavalry raids into the Caliphate territory, prompting the Muslims to push east again. The waning Shah fled from his Muslim pursuers to Hulwan in Media, but soon fled deeper into the Iranian heartland. He raised another massive army, but it was defeated by the Caliphate at the decisive Battle of Nahavand. After this disaster Yazdegerd fled to Isfahan and then to Estakhr and Kirman, being closely pursued by the attacking Arabs all the way. The Shah managed to earn the hostility of both the Governor of Kirman and then Sistan. After moving to join up with the Turks at Merv, Yazdegerd was allegedly killed by a miller who did not recognize him, although the Governor of Merv may have been the real murderer. However, this was not the end of the House of Sasan, as the Sassanids had long engaged in diplomacy with rulres as far as India and China (engaging in contact with Northern Wei and other barbarian dynasties from 455 onwards).
Later Sassanid reconquest attempts[]
Yazdegerd's eldest son Peroz III took shelter in Tocharistan in northern Bactria, and local rulers send troops and money to him, allowing him to establish himself in eastern Sistan Province. In 661, he sent emissaries to Tang China to request military intervention against the Muslims. The Chinese refused to help take back the empire, but they recognized Peroz as the ruler of Zaranj. Emperor Gaozong of Tang regarded Peroz as King of Persia, and, in 663, after Arab forces pushed further to the east and defeated Peroz, Peroz fled into the Tarim Basim and to the Tang court at Chang'an, where he was appointed a Tang general. In 677, he built a Persian temple in Chang'an either as a Persian fire temple or a Christian church. In 679, Peroz died of disease and was given a simple burial as he had requested, and the entire Sassanid court-in-exile was in attendance. The Sassanid exiles were ordered to contribute to China and serve the Empire, and Peroz's son Narsieh was given an army by the Tang general Pei Xingjian to liberate Persia from Muslim rule. The Perso-Chinese army marched through the Tarim Basin, and Pei betrayed the trust of the Western Turkic Khaganate by surprising and conquering them. The Chinese army then abandoned Narsieh and focused on reinforcing the newly conquered regions, and Narsieh never reached Persia, instead fighting against the Arabs in the eastern provinces for 20 years with the help of friendly Turkish chieftains. He returned to China in 708, and he died not long after. The Sassanid pretender Khosrau attempted to take Persia again in 728 with Turkish support, but his attempt collapsed quickly. The An Lushan Rebellion ended Tang China's ability to fund the Sassanid nobles, and Persia was confirmed as an Islamic region.