View source for Muslim conquest of Persia

{{Short description|Rashidun Caliphate's conquest of the Sasanian Empire}}
{{Use dmy dates|date=December 2024}}
{{Use Oxford spelling|date=April 2021}}
{{Lead too long|date=December 2025}}
{{Infobox military conflict
| image             = IslamicConquestsIroon.png
| caption           = Map of [[West Asia]], depicting the approximate territorial boundaries of the [[Byzantine Empire]], the [[Rashidun Caliphate]], and the [[Sasanian Empire]] prior to the Muslim conquests
| conflict          = Muslim conquest of Persia
| partof            = the [[early Muslim conquests]]
| date              = 633–651{{sfn|Pourshariati|2008|pp=469}}
| place             = [[Mesopotamia]], [[Caucasus]], [[Persia]], and [[Greater Khorasan]]
| result            = Muslim victory
| territory         = {{bulletedlist
| Fall of [[Sasanian Empire]]
| Expansion of the Rashidun Caliphate into the [[Iranian Plateau]]}}
| combatant1        = [[Rashidun Caliphate]]
| combatant2        = {{plainlist|
*[[Sasanian Empire]]
*[[Caucasian Albania]]
*(633–636)
*[[Lakhmids]]
*(633–637)
*[[Kanarang|Kanārangīyāns]]
*(633–651)
*[[House of Ispahbudhan]]
*(633–651)
*[[House of Mihran]]
*(633–651)
*[[House of Karen]]
*(633–654)
*[[Dabuyids]]
*(642–651)
*[[Western Turkic Khaganate]]
*(651)
*[[Hephthalites]]
*(651–654)
*<small>'''Supported by:'''</small>
*[[File:Byzantine Calvary cross potent (transparent).png|10px]] '''[[Byzantine Empire under the Heraclian dynasty|Byzantine Empire]]''' (until 641)
}}
| commander1        = {{Collapsible list|title=''See list''|1= [[Abu Bakr|Abu Bakr Al Siddiq]]{{Natural Causes|bold=yes}}
{{plainlist|
*[[Umar ibn al-Khattab|Umar ibn al-Khattab]]{{Assassinated}}
*[[Uthman ibn Affan|Uthman ibn Affan]]
*[[Khalid ibn al-Walid|Khalid ibn al-Walid]]
*<small>(633–634)</small>
*[[al-Muthanna ibn Haritha|al-Muthanna ibn Haritha]]{{WIA}}
*[[Abu Ubayd al-Thaqafi|Abu Ubayd al-Thaqafi]]{{KIA}}
*[[Sa'd ibn Abi Waqqas|Sa'd ibn Abi Waqqas]]
*[[Hashim ibn Utba|Hashim ibn Utba]]
*[[Shurahbil ibn Simt|Shurahbil Simt]]
*[[Tulayha ibn Khuwaylid ibn Nawfal al-Asadi|Tulayha al-Asadi]]{{KIA}}
*[[Amr ibn Ma'adi Yakrib|Amr Yakrib]]{{KIA}}
*[[Abu Musa al-Ash'ari|Abu al-Ash'ari]]
*[[Ammar ibn Yasir|Ammar Yasir]]
*[[Al-Nu'man ibn Muqrin|Al-Nu'man Muqrin]]{{KIA}}
*[[Al-Ala al-Hadhrami]]
*[[Arfajah]]
*[[Hudhayfah ibn al-Yaman|Hudhayfah al-Yaman]]
*[[Al-Mughira ibn Shu'ba|Al-Mughira Shu'ba]]
*[[Uthman ibn Abi al-As|Uthman Abi al-As]]
*[[Al-Qa'qa' ibn Amr al-Tamimi|Al-Qa'qa' al-Tamimi]]
*[[Asim ibn 'Amr al-Tamimi|Asim al-Tamimi]]
*[[Iyad ibn Ghanm|Iyad Ghanm]]
*[[Khalid ibn Urfuta|Khalid Urfuta]]
*[[Ahnaf ibn Qais|Ahnaf Qais]]
*[[Abd Allah ibn Amir|Abd Allah Amir]]
*[[Bukayr ibn Abdallah|Bukayr Abdallah]]
*[[Kanadbak]]
*[[Busbuhra]]
*<small>(briefly)</small>
*[[Farrukhzad]]}}<small>(briefly)</small>
}}
| commander2        = {{Collapsible list|title=''See list''|1={{plainlist|
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Yazdegerd III]]{{Assassinated}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Rostam Farrokhzad]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Farrukhzad]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Hormozd Jadhuyih]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Bahman Jadhuyih]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Andarzaghar]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Piruz Khosrow]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Jaban]]{{POW}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mihran Bahram-i Chubin]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Hormuzan]]{{POW}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mardanshah]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Bahram]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Isfandiyar (Sasanian commander)|Isfandiyar]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Jalinus]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mihran Razi]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Azadbeh]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Siyavakhsh]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Shahriyar bin Kanara|Shahriyar Kanara]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Busbuhra]]{{DOW}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Shahriyar of Derbent]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mihran-i Hamadani]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Shahrvaraz Jadhuyih]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mushegh III Mamikonian|Mushegh III]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Muta (Dailamite)|Muta]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Narsi]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Kanadbak]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mardanshah of Damavand]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Javanshir]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Burzin Shah]]
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Mahoe Suri]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Siyah al-Uswari]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Aparviz of Sistan|Aparviz]]{{surrender}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Shahrag]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Faylakan]]{{KIA}}
*{{flagicon image|Derafsh Kaviani flag of the late Sassanid Empire.svg}} [[Yazdanfar]]{{surrender}}
----
*[[File:Byzantine Calvary cross potent (transparent).png|10px]] '''[[Heraclius|Emperor Heraclius]]'''
*<small>(until 641)</small>}}
}}
| strength1         = 18,000 men in [[Iraq]]<ref>{{Cite book |last=Galbinst |first=Yuri |url=https://books.google.com/books?id=fePNDwAAQBAJ |title=Fra Rashidun kalifat til abbasid kalifat |publisher=Cambridge Stanford Books |language=da |chapter=Conquest of the Sassanid Empire}}</ref>
| strength2         = Unknown
| casualties1       = 
| casualties2       = 
}}
{{Campaignbox Muslim conquest of Persia}}
{{Campaignbox Early Muslim Expansions}}
The '''Muslim conquest of Persia''' or '''Arab conquest of Iran''' occurred 622 and 654, when the [[Rashidun Caliphate]] conquered the [[Sasanian Empire]] as part of the [[early Muslim conquests]], which began under [[Muhammad]] in 622.

While [[Pre-Islamic Arabia|Arabia]] was witnessing the rise of [[Islam]] in the 7th century, Persia was struggling with unprecedented political, economic and social issues as well as military weakness; the [[Military of the Sasanian Empire|Sasanian army]] had greatly exhausted itself in the [[Byzantine–Sasanian War of 602–628]]. Following the execution of Sasanian shah [[Khosrow II]] in 628, Persia's internal political stability began to deteriorate rapidly, leading to ten new royal claimants being enthroned within the next four years.<ref name="ReferenceA">The Muslim Conquest of Persia By A.I. Akram. Ch: 1 </ref>{{bsn|date=December 2025}} Shortly afterwards, Persia was further devastated by the [[Sasanian civil war of 628–632|Sasanian Interregnum]], a large-scale civil war that began in 628 and resulted in the government's decentralization by 632.

Amidst Persia's turmoil, the first Rashidun invasion of Sasanian territory took place in 633, when the [[Rashidun army]] conquered parts of [[Asoristan]], which was the Sasanians' political and economic centre in [[Mesopotamia]].<ref>{{cite book|url=https://archive.org/details/betweenmemorydes1999hump |url-access=registration |page=[https://archive.org/details/betweenmemorydes1999hump/page/180 180] |title=Between Memory and Desire|via=Internet Archive |publisher=University of California Press |isbn=9780520214118|last1=Stephen Humphreys|first1=R.|date=January 1999}}</ref> Later, the regional Rashidun army commander [[Khalid ibn al-Walid]] was transferred to oversee the [[Muslim conquest of the Levant]], and as the Rashidun army became increasingly focused on the [[Byzantine Empire]], the newly conquered Mesopotamian territories were retaken by the Sasanian army. The second Rashidun invasion began in 636, under [[Sa'd ibn Abi Waqqas]], when a decisive victory at the [[Battle of al-Qadisiyyah]], put a permanent end to any Sasanian control west of modern-day [[Iran]]. For the next six years, the [[Zagros Mountains]], a natural barrier, marked the political boundary between the Rashidun Caliphate and the Sasanian Empire. In 642, [[Umar|Umar ibn al-Khattab]], eight years into his reign as Islam's second [[Caliphate|caliph]], ordered a full-scale invasion of the rest of the [[Sasanian Empire]]. Directing the war from the city of [[Medina]] in Arabia, Umar's quick conquest of Persia in a series of coordinated and multi-pronged attacks became his greatest triumph, contributing to his reputation as a great military and political strategist.<ref name="ReferenceA"/>{{bsn|date=December 2025}} In 644, however, he was assassinated by the Persian craftsman [[Abu Lu'lu'a Firuz]], who had been captured by Rashidun troops and brought to Arabia as a slave.

Some Iranian historians have defended their forefathers by using Arab sources to illustrate that "contrary to the claims of some historians, Iranians, in fact, fought long and hard against the invading Arabs."<ref>Milani A. ''Lost Wisdom''. 2004 {{ISBN|978-0-934211-90-1}} p.15</ref> By 651, most of the urban centres in Iranian lands, with the notable exception of the provinces along the [[Caspian Sea]] such as [[Tabaristan]] and [[Transoxiana]], had come under Muslim domination. Many localities fought against the invaders; although the Rashidun army had established hegemony over most of the country, many cities rose in rebellion by killing their Arab governors or attacking their garrisons. Eventually, military reinforcements quashed the Iranian insurgencies and imposed complete control. The [[Islamization of Iran]] was gradual and incentivized in various ways over a period of centuries, though some Iranians never converted and there is widespread evidence of [[Avesta|Zoroastrian scriptures]] and all other pre-Islamic being systematically burnt and [[Magi|Zoroastrian priests]] being executed, particularly in areas that were centers of resistance.<ref>(Balāḏori, Fotuḥ, p.&nbsp;421; Biruni, Āṯār, p.&nbsp;35)</ref> Islam had become Iran's predominant religion by the [[Late Middle Ages]];<ref>Mohammad Mohammadi Malayeri, ''Tarikh-i Farhang-i Iran'' (Iran's Cultural History). 4 volumes. Tehran. 1982.</ref><ref>{{cite book |author=ʻAbd al-Ḥusayn Zarrīnʹkūb |author-link=Abdolhossein Zarinkoob |title=Dū qarn-i sukūt : sarguz̲asht-i ḥavādis̲ va awz̤āʻ-i tārīkhī dar dū qarn-i avval-i Islām (Two Centuries of Silence) |location=Tihrān |publisher=Sukhan |year=2000 |orig-year=1379 |oclc=46632917}}</ref> the majority of Iranians were [[Sunni Islam|Sunni Muslims]] until the [[Safavid conversion of Iran to Shia Islam|Safavids forcefully converted Iran to Shia Islam]] in the 16th century.

This was the first time since the collapse of the [[Neo-Babylonian Empire]] in 539 BC at the [[Battle of Opis]], that Mesopotamia was ruled again by [[Semitic languages|Semitic]]-speaking people. This was after centuries of Persian rule under the [[Achaemenid Empire|Achaemenid]], [[Parthian Empire|Parthian]] and [[Sasanian Empire|Sasanian]] empires, as well as the Greco-Roman [[Macedonian Empire|Macedonian]], [[Seleucid Empire|Seleucid]], and [[Roman Empire|Roman]] empires.

This event led to the decline of [[Zoroastrianism]], which had been the official religion of [[Name of Iran|Persia (or Iran]]) since the time of the [[Achaemenid Empire]], circa 550 BC. The [[persecution of Zoroastrians]] by the [[early Muslims]] during and after this conflict prompted many of them to flee eastward to [[Indian subcontinent|India]], where they were [[Zoroastrianism in India|taken as refugees by various kings]].

==Historiography and recent scholarship==
{{more citations needed section|date=June 2018}}
When Western academics first investigated the [[Muslim]] conquest of [[Medieval Persia|Persia]], they relied solely on the accounts of the [[Armenian people|Armenian]] [[Christians|Christian]] bishop [[Sebeos]], and accounts in Arabic written some time after the events they describe. The most significant work was probably that of [[Arthur Christensen]], and his ''L’Iran sous les Sassanides'', published in [[Copenhagen]] and [[Paris]] in 1944.<ref>Arthur Christensen, ''L’Iran sous les Sassanides'', Copenhagen, 1944 (Christensen 1944).</ref>

Recent scholarship has begun to question the traditional narrative: [[Parvaneh Pourshariati]], in her ''Decline and Fall of the Sasanian Empire: The Sasanian-Parthian Confederacy and the Arab Conquest of Iran'', published in 2008, provides both a detailed overview of the problematic nature of trying to establish exactly what happened, and a great deal of original research that questions fundamental facts of the traditional narrative, including the timeline and specific dates.

Pourshariati's central thesis is that contrary to what was commonly assumed, the Sassanian Empire was highly decentralized, and was in fact a "confederation" with the [[Parthian Empire|Parthians]], who themselves retained a high level of independence.<ref name="auto1">Parvaneh Pourshariati, ''Decline and Fall of the Sasanian Empire'', (I.B.Tauris, 2009), 3.</ref> Despite their recent victories over the [[Byzantine Empire]], the Parthians unexpectedly withdrew from the confederation, and the Sassanians were thus ill-prepared and ill-equipped to mount an effective and cohesive defense against the [[Muslim]] armies.<ref name="auto">Parvaneh Pourshariati, ''Decline and Fall of the Sasanian Empire: The Sasanian-Parthian Confederacy and the Arab Conquest of Iran'', I.B. Tauris, 2008.</ref> Moreover, the powerful northern and eastern Parthian families, the kust-i khwarasan and kust-i adurbadagan, withdrew to their respective strongholds and made peace with the Arabs, refusing to fight alongside the [[Sasanian Empire|Sassanians]].

Another important theme of Pourshariati's study is a re-evaluation of the traditional timeline. Pourshariati argues that the [[Arab conquest of Mesopotamia]] "took place, not, as has been conventionally believed, in the years 632–634, after the accession of the last Sasanian king [[Yazdgerd III]] (632–651) to power, but in the period from 628 to 632."<ref name="Parvaneh Pourshariati 2008. p. 4">Parvaneh Pourshariati, ''Decline and Fall of the Sasanian Empire: The Sasanian-Parthian Confederacy and the Arab Conquest of Iran'', I.B. Tauris, 2008. (p. 4)</ref> An important consequence of this change in timeline means that the [[Arab]] conquest started precisely when the Sassanians and Parthians were engaged in internecine warfare over succession to the Sassanian throne.<ref name="Parvaneh Pourshariati 2008. p. 4"/>

==Sasanian Empire before the conquest==
Since the [[1st century BC]], the border between the [[Roman Empire|Roman]] (later [[Byzantine Empire|Byzantine]]) and [[Parthian Empire|Parthian]] (later [[Sasanian Empire|Sasanian]]) empires had been the [[Euphrates]] River. The border was constantly contested. Most battles, and thus most fortifications, were concentrated in the hilly regions of the north, as the vast Arabian or [[Syrian Desert]] (Roman Arabia) separated the rival empires in the south. The only dangers expected from the south were occasional raids by nomadic [[Arab]] tribesmen. Both empires therefore allied themselves with small, semi-independent Arab principalities, which served as buffer states and protected Byzantium and Persia from [[Bedouin]] attacks. The Byzantine clients were the [[Ghassanid]]s; the Persian clients were the [[Lakhmid]]s. The Ghassanids and Lakhmids feuded constantly, which kept them occupied, but that did not greatly affect the Byzantines or the Persians. In the 6th and 7th centuries, various factors destroyed the balance of power that had held for so many centuries.

The conflict with the Byzantines greatly contributed to its weakness, by draining Sassanid resources, leaving it a prime target for the Muslims.

===Social problems===
Sasanian society was divided into four classes: priests, warriors, secretaries, and commoners. The latter formed the bulk of the population, served as its sole tax base, and remained its poorest class.

At the climax of [[Khosrow II|Khosrow II's]] ambitious Byzantine territory conquests in the [[Levant]] and much of [[Asia Minor]], taxes rose dramatically, and most people could not pay. Years of Sassanid-Byzantine wars had ruined trade routes and industry, the population's main income sources. The existing Sassanid administrative structure proved inadequate when faced with the combined demands of a suddenly expanded empire, economy, and population.<ref>Khodadad Rezakhani, "Arab Conquests and Sasanian Iran" page 34 "History Today" April 2017</ref> Rapid turnover of rulers and increasing provincial landholder ([[dehqan]]) power further diminished the Sasanians. Over a period of fourteen years and twelve successive kings, the Sassanid Empire weakened considerably, and the power of the central authority passed into the hands of its generals. Even when a strong king emerged following a series of coups, the [[Sassanids]] never completely recovered.

===Events===
====Revolt of the Arab client states (602)====
[[File:The assassination of Chosroës Parvez.jpg|thumb|right|The assassination of Khosrau II in a manuscript of the ''[[Shahnameh of Shah Tahmasp]]'' made by [[Abd al-Samad]] c.&nbsp;1535]]

The Byzantine clients, the Arab [[Ghassanids]], converted to the [[Monophysite]] form of [[Christianity]], which was regarded as [[Heresy|heretical]] by the established Byzantine [[Eastern Orthodox Church]]. The Byzantines attempted to suppress the heresy, alienating the Ghassanids and sparking rebellions on their desert frontiers. The [[Lakhmids]] also revolted against the Persian king Khusrau II. [[Nu'man III]] (son of Al-Monder IV), the first Christian Lakhmid king, was deposed and killed by [[Khusrau II]] in 602, because of his attempt to throw off Persian suzerainty. After Khusrau's assassination in 628, the Persian Empire fractured and the [[Lakhmids]] were effectively semi-independent. It is now widely believed that the annexation of the Lakhmid kingdom was one of the main factors behind the fall of the Sasanian Empire and the subsequent Islamic conquest of Persia, as the [[Lakhmid]]s agreed to act as spies for the [[Muslims]] after being defeated in the [[Battle of Hira]] by [[Khalid ibn al-Walid]].<ref>Iraq After the Muslim Conquest By [[Michael G. Morony]], pg. 233</ref>

====Byzantine–Sassanid War (602–628)====
{{Main|Byzantine-Sassanid War of 602–628}}

The Persian ruler [[Khosrau II|Khosrau II (Parviz)]] defeated a dangerous rebellion within his own empire, [[Bahram Chobin]]'s rebellion. He then turned his focus to his traditional Byzantine enemies, leading to the [[Byzantine-Sassanid War of 602–628]]. For a few years, he succeeded. From 612 to 622, he extended the Persian borders almost to the same extent that they were under the [[Achaemenids|Achaemenid dynasty]] (550–330&nbsp;BC), capturing Western states as far as [[Roman Egypt|Egypt]], [[Palestine (region)|Palestine]] (the conquest of the latter being assisted by a Jewish army), and more.

The Byzantines regrouped and pushed back in 622 under [[Heraclius]]. Khosrau was defeated at the [[Battle of Nineveh (627)|Battle of Nineveh]] in 627, and the Byzantines recaptured all of [[Syria (region)|Syria]] and penetrated far into the Persian provinces of [[Mesopotamia]]. In 629, Khosrau's general [[Shahrbaraz]] agreed to peace, and the border between the two empires was once again the same as it had been in 602.

====Plague of Sheroe====
{{main|Plague of Sheroe}}

The Plague of Sheroe (627–628) was one of several epidemics that occurred in or close to Iran within two centuries after the first epidemic was brought by the Sasanian armies from its campaigns in [[Constantinople]], [[Syria (region)|Syria]], and [[Kingdom of Armenia (antiquity)|Armenia]].{{sfn|Christensen|1993|p=81}} It caused the death of many Aryan and therefore contributed to the fall of the Sasanian Empire.

====Execution of Khosrau II====
{{See also|Sasanian civil war of 628–632}}
[[Khosrau II]] was executed in 628 and, as a result, there were numerous claimants to the throne; from 628 to 632 there were ten kings and queens of Persia. The last, [[Yazdegerd III of Persia|Yazdegerd III]], was a grandson of Khosrau II and was said to be a mere child aged 8 years.<ref name="EIr-Sasanian">{{harvnb|Shapur Shahbazi|2005}}</ref>

====Muhammad's Letter====
After the [[Treaty of Hudaybiyyah]] in 628, Islamic tradition holds that [[Muhammad]] sent many letters to the princes, kings, and chiefs of the various tribes and kingdoms of the time, exhorting them to convert to Islam and bow to the order of God. These letters were carried by ambassadors to [[Greater Iran|Persia]], [[Byzantine Empire|Byzantium]], [[Kingdom of Aksum|Ethiopia]], [[Sasanian Egypt|Egypt]], [[Greater Yemen|Yemen]], and the city of [[Al-Hirah]] in Iraq on the same day.<ref name="seventhyear">{{cite web | url=http://www.al-islam.org/message/43.htm | title=The Events of the Seventh Year of Migration | publisher=[[Ahlul Bayt Digital Islamic Library Project]] | access-date=3 April 2007 | archive-url=https://web.archive.org/web/20120805184742/http://www.al-islam.org/message/43.htm | archive-date=5 August 2012 | url-status=dead }}</ref> This assertion has been brought under scrutiny by some modern historians of Islam—notably Grimme and Caetani.<ref>Leone Caetani, Annali dell' Islam, vol. 4, p. 74</ref> Particularly in dispute is the assertion that Khosrau II received a letter from Muhammad, as the Sassanid court ceremony was notoriously intricate, and it is unlikely that a letter from what at the time was a minor regional power would have reached the hands of the Shahanshah.<ref>Leone Caetani, ''Annali dell'Islam'', vol. 2, chapter 1, paragraph 45–46</ref>

With regards to Persia, Muslim histories further recount that at the beginning of the seventh year of migration, Muhammad appointed one of his officers, Abdullah Huzafah Sahmi Qarashi, to carry his letter to [[Khosrow II]] inviting him to convert:

{{blockquote|In the name of God, the Beneficent, the Merciful.

From Muhammad, the Messenger of God, to the great Kisra of Persia. Peace be upon him, who seeks truth and expresses belief in God and in His Prophet and testifies that there are no gods but one God whom has no partners, and who believes that Muhammad is His servant and Prophet. Under the Command of God, I invite you to Him. He has sent me for the guidance of all people so that I may warn them all of His wrath and may present the unbelievers with an ultimatum. Embrace Islam so that you may remain safe. And if you refuse to accept Islam, you will be responsible for the sins of the Magi.<ref>''Tabaqat-i Kubra, vol. I, page 360; Tarikh-i Tabari, vol. II, pp. 295, 296; Tarikh-i Kamil, vol. II, page 81 and Biharul Anwar, vol. XX, page 389''</ref>|author=|title=|source=}}

There are differing accounts of the reaction of [[Khosrow II]].<ref>"Kisra", M. Morony, ''The Encyclopaedia of Islam'', Vol. V, ed.C.E. Bosworth, E.van Donzel, B. Lewis and C. Pellat, (E.J.Brill, 1980), 185.[https://books.google.com/books?id=xJY3AAAAIAAJ&pg=PA185] {{Webarchive|url=https://web.archive.org/web/20230811084225/https://books.google.com/books?id=xJY3AAAAIAAJ&pg=PA185|date=11 August 2023}}</ref>

===Military===
{{more citations needed section|date=December 2020}}
Years of warfare between the Sasanians and the Byzantines, as well as the strain of the [[Third Perso-Turkic War|Khazar invasion of Transcaucasia]], had exhausted the army. No effective ruler followed [[Khosrau II]], causing chaos in society and problems in the provincial administration, until [[Yazdegerd III]] rose to power. All these factors undermined the strength of the Persian army. Yazdegerd III was merely 8 years old when he came to the throne and, lacking experience, did not try to rebuild the army. The Sasanian Empire was highly decentralized, and was in fact a "confederation" with the [[Parthian Empire|Parthians]], who themselves retained a high level of independence.<ref name="auto1"/> After the last Sasanian-Byzantine war, the Parthians wanted to withdraw from the confederation, and the Sasanians were thus ill-prepared and ill-equipped to mount an effective and cohesive defense against the [[Muslim]] armies.<ref name="auto"/> Moreover, the powerful northern and eastern Parthian families, the Kust-i Khwarasan and Kust-i Adurbadagan, withdrew to their respective strongholds and made peace with the Arabs, refusing to fight alongside the [[Sasanians]].

Pourshariati argues that the [[Arab conquest of Mesopotamia]] "took place, not, as has been conventionally believed, in the years 632–634, after the accession of the last Sasanian king [[Yazdgerd III]] (632–651) to power, but in the period from 628 to 632."<ref name="Parvaneh Pourshariati 2008. p. 4"/> An important consequence of this change in timeline means that the [[Arab]] conquest started precisely when the Sasanians and Parthians were engaged in internecine warfare over who was to succeed the Sasanian throne.<ref name="Parvaneh Pourshariati 2008. p. 4"/>

When Arab squadrons made their first raids into Sasanian territory, Yazdegerd III did not consider them a threat, and he refused to send an army to encounter the invaders. When the main Arab army reached the Persian borders, Yazdegerd III procrastinated in dispatching an army against the Arabs. Even [[Rostam-e Farokhzad]], who was both [[Spahbod|Eran Spahbod]] and [[Viceroy]], did not see the Arabs as a threat. Without opposition, the Arabs had time to consolidate and fortify their positions.

When hostilities between the Sasanians and the Arabs finally began, the Persian army faced fundamental problems. While their [[heavy cavalry]] had proved effective against the Roman forces, it was too slow and regimented to act with full force against the agile and unpredictable lightly armed Arab cavalry and foot archers.

The Persian army had a few initial successes. War elephants temporarily halted the Arab army, but when Arab veterans returned from the Syrian fronts, where they had been fighting against Byzantine forces, they provided crucial instruction on how to effectively counter the war elephants.

These factors contributed to the decisive Sassanid defeat at the Battle of al-Qādisiyyah. The Persians, who had only one generation before conquered Egypt and Asia Minor, lost decisive battles when nimble, lightly armed Arabs accustomed to skirmishes and desert warfare attacked them. The Arab squadrons defeated the Persian army in several more battles culminating in the [[Battle of Nahāvand]], the last major battle of the Sassanids. The Sassanid dynasty came to an end with the death of Yazdegerd III in 651.

==Succession of Muhammad==
{{Main|Succession of Muhammad}}
[[Muhammad]] died in June 632, and [[Abu Bakr]] took the title of [[Caliph]] and political successor at [[Medina]]. Soon after [[Abu Bakr]]'s succession, several Arab tribes revolted, in the [[Ridda Wars]] ([[Arabic]] for the Wars of Apostasy). The Ridda Wars preoccupied the [[Caliphate]] until March 633, and ended with the entirety of the Arab Peninsula under the authority of the Caliph at Medina.

Abu Bakr set in motion a historical trajectory (continued later by Umar and Uthman) that in a few decades led to one of the [[List of largest empires|largest empires in history]],<ref name="Donner">Fred M. Donner, "Muhammad and the Believers: At the Origins of Islam", Harvard University Press, 2010, {{ISBN|978-0-674-05097-6}} ''[https://books.google.com/books?id=qBzRj7OajmEC&pg=PP1] {{Webarchive|url=https://web.archive.org/web/20230811084226/https://books.google.com/books?id=qBzRj7OajmEC&pg=PP1|date=11 August 2023}}''</ref> beginning with a confrontation with the Sassanid Empire under the general [[Khalid ibn al-Walid]].

==Conquest of Mesopotamia (633–638)==
{{Main|Arab conquest of Mesopotamia}}

===First invasion (633)===
[[File:Mohammad adil-Khalid's conquest of Iraq.PNG|thumb|Map detailing the route of [[Khalid ibn al-Walid]]'s conquest of [[Mesopotamia]]]]

After the [[Ridda wars]], a tribal chief of northeastern Arabia, [[Al-Muthanna ibn Haritha]], raided the Sasanian towns in [[Mesopotamia]], actions that generated a considerable amount of booty was collected.<ref name="Najeebabadi">Akbar Shah Najeebabadi, The history of Islam. B0006RTNB4.</ref> Al-Muthanna ibn Haritha went to Medina to inform Abu Bakr about his success and was appointed commander of his people, after which he began to raid deeper into Mesopotamia. Using the mobility of his [[light cavalry]], he could easily raid any town near the desert and disappear again into the desert, beyond the reach of the [[Military of the Sasanian Empire|Sasanian army]]. Al-Muthanna's acts made Abu Bakr think about the expansion of the [[Rashidun Caliphate]].<ref name="Tabari">Tabari: Vol. 2, p. 554.</ref>

To ensure victory, Abu Bakr used a volunteer army and put his best general, [[Khalid ibn al-Walid]], in command. After defeating the self-proclaimed prophet [[Musaylimah]] in the [[Battle of Yamama]], Khalid was still at [[Al-Yamama]] when Abu Bakr ordered him to invade the Sasanian Empire. Making [[Al-Hirah]] the objective of Khalid, Abu Bakr sent reinforcements and ordered the tribal chiefs of northeastern Arabia, Al-Muthanna ibn Haritha, Mazhur bin Adi, Harmala and Sulma to operate under Khalid's command. Around the third week of March 633 (first week of [[Muharram]] 12th Hijrah) Khalid set out from Al-Yamama with an army of 10,000.<ref name="Tabari"/> The tribal chiefs, with 2,000 warriors each, joined him, swelling his ranks to 18,000. After entering Mesopotamia, he dispatched messages to every governor and deputy who ruled the provinces calling on them to either embrace Islam or pay tribute. Khalid did not receive any responses and continued with his tactical plans.<ref>{{cite book |last1=Khalid |title=Men Around the Messenger |publisher=Al Manar |pages=234}}</ref>

Khalid went on to win decisive victories in four consecutive battles: the [[Battle of Chains]], fought in April; the [[Battle of River]], fought in the third week of April; the [[Battle of Walaja]] the following month (where he successfully used a [[Pincer movement|double envelopment]] manoeuvre), and the [[Battle of Ullais]], fought in mid-May. The Persian court, already disturbed by internal problems, was thrown into chaos. In the last week of May, the important city of [[Al-Hirah]] [[Battle of Hira|fell to the Muslims]]. After resting his armies, in June, Khalid [[Battle of Al-Anbar|laid siege]] to the city of [[Anbar (town)|al-Anbar]], which surrendered in July. Khalid then moved south, and [[Battle of Ayn al-Tamr|conquered the city of Ayn al-Tamr]] in the last week of July. At this point, most of what is now Iraq was under Islamic control.

Khalid received a call for aid from northern Arabia at Dawmat al-Jandal, where another Muslim Arab general, [[Iyad ibn Ghanm]], was trapped among the rebel tribes. Khalid went there and defeated the rebels in the [[Battle of Dawmat al-Jandal]] in the last week of August. Upon his return, he received news of the assembling of a large Persian army. He decided to defeat them all separately to avoid the risk of being defeated by a large unified Persian army. Four divisions of Persian and Christian Arab auxiliaries were present at Hanafiz, Zumiel, Sanni and Muzieh. Khalid divided his army into three units, and employed them in well-coordinated attacks against the Persians from three different sides at night, in the [[Battle of Muzayyah]], then the [[Battle of Saniyy]], and finally the [[Battle of Zumail]], all during the month of November. These devastating defeats ended Persian control over Mesopotamia, and left the Persian capital [[Ctesiphon]] vulnerable. Before attacking Ctesiphon, Khalid decided to eliminate all Persian forces in the south and west. He accordingly [[Battle of Firaz|marched against the border city of Firaz]], where he allegedly defeated the [[Military of the Sasanian Empire|combined forces of the Sasanian Persians]], the [[Byzantine army|Byzantine]]s and [[Christian Arabs]] in December. However this has been disputed, as there is doubt to any large-scale Persian forces, and the suspect elements of the battle including casualty numbers and a lack of names of allied commanders point to an Islamic cover-up, which may have in fact been a defeat of Khalid.<ref name=":0">{{Citation |last=Takirtakoglou |first=Konstantinos |title=The Battle of Firāḍ: The Day on Which Khālid b. al-Walīd Did [Not] Defeat Both Byzantines and Persians |date=2021 |work=Journal of Medieval Military History: Volume XIX |pages=1–20 |editor-last=Rogers |editor-first=Clifford J. |url=https://www.cambridge.org/core/books/journal-of-medieval-military-history/battle-of-firad-the-day-on-which-khalid-b-alwalid-did-not-defeat-both-byzantines-and-persians/476A229E680237670593FEF5103A7AF7 |access-date=2024-06-16 |publisher=Boydell & Brewer |isbn=978-1-80010-228-6 |editor2-last=France |editor2-first=John |editor3-last=DeVries |editor3-first=Kelly}}</ref> This battle was the last in his conquest of Mesopotamia. While Khalid was on his way to attack Qadissiyah (a key fort en route to Ctesiphon), Abu Bakr ordered him to the Roman front in Syria to assume command there.<ref>Akram, chapters 19–26.</ref>

===Second invasion (634–636)===
====Battle of the Bridge====
{{main|Battle of the Bridge}}

According to the will of Abu Bakr, Umar was to continue the conquest of Syria and Mesopotamia. On the northeastern borders of the Empire, in Mesopotamia, the situation was rapidly deteriorating. During [[Abu Bakr]]'s era, [[Khalid ibn al-Walid]] had left Mesopotamia with half his army of 9000 soldiers to assume command in Syria, whereupon the Persians decided to take back their lost territory. The Muslim army was forced to leave the conquered areas and concentrate on the border. Umar immediately sent reinforcements to aid Muthanna ibn Haritha in Mesopotamia under the command of [[Abu Ubaid al-Thaqafi]].<ref name="ReferenceA"/>{{bsn|date=December 2025}} At that time, a series of battles between the Persians and Arabs occurred in the region of [[Sawad]], such as [[Battle of Namaraq|Namaraq]], [[Battle of Kaskar|Kaskar]] and Baqusiatha, in which the Arabs managed to maintain their presence in the area.<ref>{{cite book|author=نجاة سليم محاسيس|title=معجم المعارك التاريخية|publisher=Al Manhal|year=2011|page=285|language=ar|isbn=9796500011615}}</ref> Later on, the Persians defeated Abu Ubaid in the [[Battle of the Bridge]]. Muthanna bin Haritha was later victorious in the [[Battle of Buwayb]]. In 635 [[Yazdgerd III]] sought an alliance with Emperor [[Heraclius]] of the [[Eastern Roman Empire]], marrying the latter's daughter (or, by some traditions, his granddaughter) in order to seal the arrangement. While Heraclius prepared for a major offence in the Levant, Yazdegerd ordered the concentration of massive armies to push the Muslims out of Mesopotamia for good through a series of well-coordinated attacks on two fronts.

[[File:Mohammad adil rais-battlefield of qadisiyyah.PNG|thumb|right|upright|The site of the Battle of Qadisiyyah, showing Muslim army (in red) and Sasanian army (in blue)]]
[[File:Shahnameh3-1.jpg|thumb|upright|Battle of Qadisiyyah from a manuscript of the ''[[Shahnameh]]'']]

====Battle of Qadisiyyah====
{{Main|Battle of Qadisiyyah}}

Umar ordered his army to retreat to the Arabian border and began raising armies at [[Medina]] for another campaign into Mesopotamia. Owing to the critical situation, Umar wished to command the army personally, but the members of [[Majlis ash-Shura]] demurred, claiming that the two-front war required Umar's presence in Medina. Accordingly, Umar appointed [[Saad ibn Abi Waqqas]], a respected senior officer, even though Saad was suffering from sciatica.<ref>{{Cite web |url=http://www.taqawalife.com/2012/02/saad-bin-abi-waqqas-raziallah-unho.html |title=Taqawa Leads to Success: Saad Bin Abi Waqqas RaziAllah Unho |access-date=15 December 2016 |archive-url=https://web.archive.org/web/20160811140834/http://www.taqawalife.com/2012/02/saad-bin-abi-waqqas-raziallah-unho.html |archive-date=11 August 2016 |url-status=usurped }}</ref> Saad left Medina with his army in May 636 and arrived at [[Al-Qādisiyyah (historical city)|Qadisiyyah]] in June.

While Heraclius launched his offensive in May 636, Yazdegerd was unable to muster his armies in time to provide the Byzantines with Persian support. Umar, allegedly aware of this alliance and not wanting to risk a battle with two great powers simultaneously, quickly reinforced the Muslim army at [[Battle of Yarmouk|Yarmouk]] to engage and defeat the Byzantines. Meanwhile, he ordered Saad to enter into peace negotiations with Yazdegerd III and invite him to convert to [[Islam]] to prevent Persian forces from taking the field. Heraclius instructed his general [[Vahan (Byzantine commander)|Vahan]] not to engage in battle with the Muslims before receiving explicit orders. Fearing more Arab reinforcements, Vahan attacked the Muslim army in the [[Battle of Yarmouk]] in August 636, and was routed.<ref>Serat-i-Hazrat Umar-i-Farooq, by Mohammad Allias Aadil, page no:67</ref>

With the Byzantine threat ended, the Sasanian Empire was still a formidable power with vast manpower reserves, and the Arabs soon found themselves confronting a huge Persian army with troops drawn from every corner of the empire, including war elephants, and commanded by its foremost generals. Within three months, Saad defeated the Persian army in the [[Battle of al-Qādisiyyah]], effectively ending Sasanian rule west of Persia proper.<ref>{{cite book |title=The Muslim Conquest of Persia |first=A.I. |last= Akram |chapter=5 |isbn=978-0-19-597713-4|year=1975 }}</ref> This victory is largely regarded as a decisive turning point in Islam's growth: with the bulk of Persian forces defeated, Saad with his companions later conquered [[Babylon]] ([[Battle of Babylon (636)]]), [[Kutha|Kūthā]], Sābāṭ ([[Valashabad]]) and Bahurasīr ([[Veh-Ardashir]]). [[Ctesiphon]], the capital of the Sassanid Empire, [[Siege of Ctesiphon (637)|fell in March 637]] after a siege of three months.

===Final campaign and conquest (636–638)===
In December 636, Umar ordered [[Utbah ibn Ghazwan]] to head south to capture [[al-Ubulla]] (known as "port of Apologos" in the [[Periplus of the Erythraean Sea]]) and [[Basra]], in order to cut ties between the Persian garrison there and [[Ctesiphon]]. Utbah ibn Ghazwan arrived in April 637, and captured the region. The Persians withdrew to the [[Maysan Governorate|Maysan]] region, which the Muslims seized later as well.<ref>{{cite book|author=Al-Tabari|title=History of the Prophets and Kings|pages=590–595|author-link=Al-Tabari|title-link=History of the Prophets and Kings}}</ref>

After the conquest of Ctesiphon, several detachments were immediately sent west to capture [[Circesium]] and [[Hīt|Heet]], both forts at the Byzantine border. Several fortified Persian armies were still active north-east of Ctesiphon at [[Jalawla]] and north of the [[Tigris]] at [[Tikrit]] and [[Mosul]].

After withdrawal from Ctesiphon, the Persian armies gathered at Jalawla, a place of strategic importance due to routes leading from here to Mesopotamia, [[Khurasan]] and [[Iranian Azerbaijan|Azerbaijan]]. The Persian forces at Jalawla were commanded by Mihran. His deputy was Farrukhzad, a brother of Rustam, who had commanded the Persian forces at the [[Battle of al-Qadisiyyah]]. Umar decided to deal with Jalawla first, thereby clearing the way to the north, before taking any decisive action against Tikrit and Mosul. Umar appointed [[Hashim ibn Utbah]] to take Jalawla and Abdullah ibn Muta'am to conquer [[Tikrit]] and [[Mosul]]. In April 637, Hashim led 12,000 troops from Ctesiphon to win a victory over the Persians at the [[Battle of Jalula|Battle of Jalawla]]. He then laid siege to Jalawla for seven months, ending in the city's capture. Then, Abdullah ibn Muta'am marched against Tikrit and captured the city with the help of [[Christians]], after fierce resistance.{{Citation needed|date=April 2009}}  He next sent an army to [[Mosul]] which surrendered on the condition of paying [[Jizya]]. With victory at Jalawla and occupation of the Tikrit-Mosul region, the whole of Mesopotamia was under Muslim control.

Thereafter, a Muslim force under Qa'qa marched in pursuit of the escaping Persians at Khaniqeen, 25 kilometres (15&nbsp;mi) from Jalawla on the road to Iran, still under the command of Mihran. Qa'qa defeated the Persian forces in the Battle of Khaniqeen and captured the city. The Persians then withdrew to [[Hulwan]]. Qa'qa followed and laid siege to the city, which was captured in January 638.<ref>{{cite book |title=The Muslim Conquest of Persia |first=A. I. |last=Akram |chapter=6 |isbn=978-0-19-597713-4|year=1975 }}</ref> Qa'qa sought permission to operate deeper in Persia, but Umar rejected the proposal, writing in response:
{{blockquote|I wish that between the Suwad and the Persian hills there were walls which would prevent them from getting to us, and prevent us from getting to them.<ref>{{cite book |title=Al Farooq, Umar |author-link=Muhammad Husayn Haykal |first=Muhammad Husayn |last=Haykal |chapter=5 |page=130}}</ref> The fertile Suwad is sufficient for us; and I prefer the safety of the Muslims to the spoils of war.}}

==Persian raids in Mesopotamia (638–641)==
By February 638 there was a lull in the fighting on the Persian front. The Suwad, the [[Tigris]] valley, and the [[Euphrates]] valley were now under complete Muslim control. The Persians had withdrawn to [[Persia proper]], east of the [[Zagros mountains]]. The Persians continued raiding Mesopotamia, which remained politically unstable. It seemed the Zagros range was the dividing line between the [[Rashidun Caliphate]] and the Sassanids. In the latter part of 638, [[Hormuzan]], who was one of the seven great chiefs of Persia, and had commanded a corps at the [[Battle of Qadisiyyah]], intensified his raids in Mesopotamia. Saad, on Umar's instructions, attacked Hormuzan, while Utbah ibn Ghazwan, aided by Nouman ibn Muqarin, attacked [[Ahvaz]] and forced Hormuzan into a peace treaty, under which Ahvaz would remain in Hormuzan's possession as a Muslim vassal state and would pay tribute. Hormuzan broke the treaty, leading Umar to send [[Abu Musa Ashaari]], governor of [[Busra]], to deal with him. After another defeat, Hormuzan signed another treaty on similar terms to the last. This peace also proved short-lived once Hormuzan was reinforced by fresh Persian troops sent by Emperor [[Yazdgerd III]] in late 640. The troops concentrated at Tuster, north of Ahvaz. Umar sent the Governor of [[Kufa]], [[Ammar ibn Yasir]], the governor of [[Busra]], Abu Musa, and Nouman ibn Muqarin there, where Hormuzan was defeated, captured and sent to Umar in Medina.  Hormuzan apparently converted to Islam and remained a useful adviser to Umar throughout the remainder of the Persian campaign. He is also believed to be the mastermind behind Umar's assassination in 644.

After the victory at [[Tustar]], [[Abu Musa Ashaari|Abu Musa]] marched against the strategically important [[Susa]] in January 641, capturing it after a siege of a couple of months. Next, Abu Musa marched against Junde Sabur, the only place left of military importance in the Persian province of [[Khuzistan]], which surrendered to the Muslims after a siege of a few weeks.<ref>The Muslim Conquest of Persia By A.I. Akram. Ch: 7 {{ISBN|978-0-19-597713-4}}, 9780195977134</ref>

==Battle of Nahavand (642)==
{{Main|Battle of Nahavand}}

After the conquest of [[Khuzistan]], Umar wanted peace. Though considerably weakened, the image of the Persian Empire as a fearsome superpower still resonated in the minds of the newly-ascendant Arabs, and Umar was wary of unnecessary military engagement with it, preferring to leave the rump of the Persian Empire alone, commenting, "I wish there was a mountain of fire between us and the Persians, so that neither they could get to us, nor we to them."<ref name="ReferenceC">{{cite book|title=The Muslim Conquest of Persia | first=A.I.|last= Akram|chapter= 8 |isbn= 978-0-19-597713-4| year=1975}}</ref>
Persian pride was hurt by the Arab conquest, making the ''status quo'' intolerable.<ref>{{cite book|title=Dictionary of Islamic Architecture |first= Anderew|last= Petersen |page=120}}</ref>
[[File:Sassanid army helmet by Nickmard Khoey.jpg|thumb|A Sasanian army helmet.]]
After the defeat of the Persian forces at the [[Battle of Jalula]] in 637, Yazdgerd III went to [[Rey, Iran|Rey]] and from there moved to [[Merv]], where he set up his capital and directed his chiefs to conduct continuous raids in Mesopotamia. Within four years, Yazdgerd III felt powerful enough to challenge the Muslims again for control of Mesopotamia. Accordingly, he recruited 100,000 hardened veterans and young volunteers from all parts of Persia, under the command of Mardan Shah, which marched to [[Nahavand]] for the last titanic struggle with the Caliphate.

The Governor of [[Kufa]], [[Ammar ibn Yasir]], received intelligence of the Persian movements and concentration at Nahavand and reported them to Umar. Although Umar had expressed a desire for Mesopotamia to be his easternmost frontier, the concentration of the Persian army at Nahavand forced him to act.<ref>{{cite book|title=Rome's Enemies 3: Parthians and Sassanids |first= Peter|last= Wilcox|page= 4|publisher=Osprey Publishing}}</ref> He now believed that as long as Persia proper remained under Sasanian rule, the raids into Mesopotamia would continue. Hudheifa ibn Al Yaman was appointed commander of the forces of Kufa, and was ordered to march to Nahavand. Abu Musa was to march to Nahavand from [[Busra]], while [[Nouman ibn Muqarrin]] marched from Ctesiphon. Umar decided to personally take the army concentrated at Medina to Nahavand to assume overall command. The members of the Majlis al-[[Shura]] suggested that Umar should command the campaign from Medina, appointing an astute field commander for Nahavand. Umar acquiesced, appointing [[Mugheera ibn Shuba]] as commander of the forces concentrated at Medina, and Nouman ibn Muqarrin as commander-in-chief at Nahavand. The Muslim army first concentrated at Tazar, and then defeated the Persians at the [[Battle of Nahavand]] in December 642. Nouman died in the action, and, as per Umar's instructions, Hudheifa ibn Al Yaman became the new commander-in-chief. Thereafter, the Muslims captured the whole district of [[Hamadan]], encountering only feeble resistance.<ref name="ReferenceC"/>

==Preparation for the conquest of Persia==
After several years, Caliph Umar adopted a new offensive policy,<ref>''Al Farooq, Umar'' By [[Muhammad Husayn Haykal]]. chapter 18-page 130</ref> preparing to launch a full-scale invasion of what remained of the Sasanian Empire. The Battle of Nahavand was one of the most decisive battles in Islamic history<ref name="autogenerated1">{{cite book|title=The Muslim Conquest of Persia |first= A.I. |last=Akram|chapter=10|isbn= 978-0-19-597713-4|year= 1975 }}</ref> and proved to be the key to Persia. After the devastating defeat at Nahavand, the last Sassanid emperor, Yazdegerd III, fled to different parts of Persia to raise a new army, with limited success, while Umar attempted to capture him.

Umar decided to strike the Persians immediately after their defeat at Nahavand, while he still possessed a psychological advantage. Umar had to decide which of three provinces to conquer first: [[Fars province|Fars]] in the south, [[Iranian Azerbaijan|Azerbaijan]] in the north or [[Isfahan]] in the center. Umar chose Isfahan, as it was the heart of the Persian Empire and a conduit for supply and communications among the Sasanian garrisons, and its capture would isolate Fars and Azerbaijan from [[Greater Khorasan|Khorasan]], Yazdegerd's stronghold. After he had taken Fars and Isfahan, the next attacks would be simultaneously launched against Azerbaijan, the northwestern province, and [[Sistan]], the easternmost province of the Persian Empire.<ref name="autogenerated1"/> The conquest of those provinces would leave Khorasan isolated and vulnerable, the last stage of the conquest of Sassanid Persia.

Preparations were complete by January 642. The success of the plan depended upon how effectively Umar could coordinate these attacks from Medina, about 1500 kilometers from Persia, and upon the skill of his field commanders. Umar adopted a different approach to the command structure. Instead of appointing a single field commander to press the campaign, Umar appointed several commanders, each assigned a different mission. Once a commander's mission ended, he would become an ordinary soldier under the new field commander for the latter's mission. The purpose of this strategy was to allow commanders to mix with their soldiers and to remind them that they are like everyone else: command is only given to the most competent, and, once the battle is over, the commander returns to his previous position.

On the eve of the campaign, Umar, in order to boost morale, decided to reinstall Khalid as field commander, four years after his dismissal.<ref name="autogenerated1"/> Khalid's reputation as the conqueror of the Eastern Roman provinces demoralized the Persian commanders, most of whom had already been defeated by him during his conquest of Mesopotamia in 633. Before Umar could issue the reappointment order, Khalid died in [[Homs#Arab Caliphate|Emesa]].

Throughout the Persian campaign, Umar even appointed the commanders of the wings, the center and the [[cavalry]] of the army. Umar strictly instructed his commanders to consult him before making any decisive move in Persia. All the commanders, before starting their assigned campaigns, were instructed to send a detailed report of the geography and terrain of the region and the positions of the Persian [[garrison]]s, [[fort]]s, cities and troops. Umar then would send them a detailed plan of how he wanted the region to be captured. Only the tactical issues were left to the field commanders to tackle in accordance with the situation they faced at their fronts.<ref>''The History of Al-Tabari: The Challenge to the Empires'', translated by Khalid Yahya Blankinship, Published by SUNY Press, 1993, {{ISBN|978-0-7914-0852-0}},</ref> Umar appointed the best available and well-reputed commanders for the campaign.<ref name="autogenerated1"/><ref name="autogenerated2">{{cite book|title=Al Farooq, Umar|author=Muhammad Husayn Haykal| chapter =19| page =130|author-link=Muhammad Husayn Haykal}}</ref>

==Conquest of Central Iran==
[[File:Choghazanbil2.jpg|thumb|The ziggurat of [[Choqa Zanbil]] in [[Khuzestan]]]]

In the wake of Khalid's demise, Umar appointed Abdullah ibn Uthman as commander of the Muslim forces for the invasion of [[Isfahan]]. From Nahavand, Nu'man ibn Muqaarin marched to [[Hamadan]], and then proceeded 370 kilometres (230&nbsp;mi) southeast to the city of [[Isfahan]], defeating a Sasanian army there. The Sassanian commander, [[Shahrvaraz Jadhuyih]], along with another Sasanian general, was killed during the battle.<ref>Pourshariati (2008), p. 247</ref> Nu'man, reinforced by fresh troops from Busra and Kufa under the command of [[Abu Musa Ashaari]] and [[Ahnaf ibn Qais]], then besieged the city.<ref name="autogenerated3">The Muslim Conquest of Persia By A.I. Akram. Ch:11 {{ISBN|978-0-19-597713-4}},</ref> The siege continued for a few months before the city surrendered.

In 651, Nu'aym ibn Muqaarin, Nu'man's brother, marched northeast to [[Rey, Iran]], about 320 kilometres (200&nbsp;mi) from Hamadan, and laid siege to the city, which surrendered after fierce resistance. Nu'aym then marched 240 kilometres (150&nbsp;mi) northeast toward [[Qom]], which was captured without much resistance. This represented the boundary of the Isfahan region. Further northeast was [[Greater Khorasan|Khurasan]], and southeast lay [[Sistan]]. Meanwhile, Hamadan and Rey had rebelled. Umar sent Nu'aym, whose brother Nu'man had recently died, to Hamadan to crush the rebellion and clear Isfahan's western frontier. Nu'aym recaptured Hamadan after a bloody battle, and then proceeded to Rey. There too the Persians resisted but were defeated outside the fort, and the Muslims recaptured the city.<ref name="Al-Tabari 1993">The History of Al-Tabari: The Challenge to the Empires, Translated by Khalid Yahya Blankinship, Published by SUNY Press, 1993, {{ISBN|978-0-7914-0852-0}}</ref> The Persian citizens sued for peace, agreeing to pay the [[Jizya]]. From Rey, Nu'aym moved north to [[Tabaristan]], south of the [[Caspian Sea]].<ref name="Al-Tabari 1993"/> The ruler of [[Tabaristan]] then signed a peace treaty with the [[Rashidun Caliphate|Caliphate]].

==Conquest of Fars==
{{main|Arab conquest of Fars}}

===First Muslim invasion and the successful Sasanian counter-attack===
The Muslim invasion of [[Fars province|Fars]] began in 638/9, when the Rashidun governor of [[Eastern Arabia|Bahrain]], [[Al-Ala'a Al-Hadrami|al-'Ala' ibn al-Hadrami]], having defeated some rebellious Arab tribes, seized an island in the [[Persian Gulf]]. Although al-'Ala' and the rest of the Arabs had been ordered to not invade Fars or its surrounding islands, he and his men continued their raids into the province. Al-'Ala quickly prepared an army which he divided into three groups, one under al-Jarud ibn Mu'alla, the second under al-Sawwar ibn Hammam, and the third under Khulayd ibn al-Mundhir ibn Sawa.

When the first group entered Fars, it was quickly defeated and al-Jarud was killed. The same thing soon happened to the second group. Khulayd and the third group kept the defenders at bay, but were blocked from withdrawing to Bahrain by the Sasanians. Umar, having found out about al-'Ala's invasion of Fars, had him replaced with [[Sa'd ibn Abi Waqqas]] as governor. Umar then ordered [[Utbah ibn Ghazwan]] to send reinforcements to Khulayd. Once the reinforcements arrived, Khulayd and some of his men managed to withdraw to Bahrain, while the rest withdrew to [[Basra]].

===Second and last Muslim invasion===
In {{Circa|643}}, [[Uthman ibn Abi al-As]] seized [[Bishapur]], which signed a peace treaty.  In 644, al-'Ala' once again attacked Fars from Bahrain, reaching as far as [[Estakhr]], until he was repulsed by the Persian governor (''[[marzban]]'') of Fars, [[Shahrag]]. Some time later, Uthman ibn Abi al-As managed to establish a military base at [[Tawwaj]], and soon defeated and killed Shahrag near [[Reishahr|Rew-shahr]]. Persian convert to [[Islam]], Hormoz ibn Hayyan al-'Abdi, was then sent by Uthman ibn Abi al-As to attack a fortress known as Senez on the coast of Fars. After the accession of [[Uthman ibn Affan]] as the new [[Rashidun Caliph]] on 11 November, the inhabitants of Bishapur, under the leadership of Shahrag's brother, declared independence, but were defeated. The Persian historian [[al-Baladhuri]] said this occurred in 646.

In 648, 'Abd-Allah ibn al-'Ash'ari forced the governor of Estakhr, Mahak, to surrender the city. Its citizens rebelled in 649/650 while its newly appointed governor, [[Abdullah ibn Aamir|'Abd-Allah ibn 'Amir]], was trying to capture [[Firuzabad, Fars|Gor]]. The military governor of Estakhr, 'Ubayd Allah ibn Ma'mar, was defeated and killed. In 650/651, Yazdegerd went there to plan an organized resistance against the Arabs, and, after some time, went to Gor. Estakhr put up a weak resistance and was soon sacked by the Arabs, who killed over 40,000 defenders. The Arabs then quickly seized Gor, [[Kazerun]] and [[Siraf]], while Yazdegerd fled to [[Kerman province|Kerman]]. Muslim control of Fars remained shaky for a time, with several local rebellions following the conquest.

==Conquest of Kerman, Sakastan and the Caucasus==
===Conquest of Kerman===
[[File:Head horse Kerman Louvre MAO132.jpg|thumb|Sassanid era horse head found in Kerman]]

The expedition to [[Kerman]], under Suhail ibn Adi, was sent at roughly the same time as the expeditions to [[Sistan]] and [[Iranian Azerbaijan|Azerbaijan]]. Suhail marched from Busra in 643; passing through [[Shiraz]] and [[Persepolis]], he joined with other armies and then marched against Kerman, which was subdued after a pitched battle with the local garrisons.

===Conquest of Sakastan===
[[File:Sakastan Sasanian era.png|thumb|Map of [[Sakastan]] under the Sasanians]]

The Arabs were raiding Sakastan as early as Umar's caliphate. The first real invasion took place in 650, when [[Abd-Allah ibn Amir]], having secured his position in Kerman, sent an army under Mujashi ibn Mas'ud there. After crossing the [[Dasht-i Lut]] desert, Mujashi ibn Mas'ud reached Sakastan, but suffered a heavy defeat and was forced to retreat.{{sfn|Marshak|Negmatov|1996|p=449}}

One year later, Abd-Allah ibn Amir sent an army under [[Rabi ibn Ziyad Harithi]] to Sakastan. After some time, Rabi reached Zaliq, a Sakastani border town, where he forced the [[dehqan]] of the town to acknowledge Rashidun authority.  He then did the same at the fortress of Karkuya, which had a famous [[fire temple]] mentioned in the [[Tarikh-i Sistan]].{{sfn|Zarrinkub|1975|p=24}} He then seized more land in the province. Next, he besieged the provincial capital, [[Zaranj|Zrang]], and, after a heavy battle outside the city, its governor, [[Aparviz of Sakastan|Aparviz]], surrendered. When Aparviz went to Rabi ibn Ziyad to negotiate a treaty, he saw that Rabi was using the bodies of two dead soldiers as a chair. This horrified Aparviz, who, in order to spare the inhabitants of Sakastan from the Arabs, made peace with them in return for a heavy tribute of 1 million [[dirham]]s, including 1,000 slave boys (or girls) bearing 1,000 golden vessels.{{sfn|Zarrinkub|1975|p=24}}{{sfn|Morony|1986|pp=203–210}} Rabi ibn Ziyad was then appointed governor of the province.{{sfn|Marshak|Negmatov|1996|p=450}}

Eighteen months later, Rabi was summoned to [[Basra]], and was replaced by 'Abd al-Rahman ibn Samura. The inhabitants of Sakastan used this opportunity to rebel, defeating the Muslim garrison at Zrang. When 'Abd al-Rahman ibn Samura reached Sakastan, he suppressed the rebellion and defeated the [[Zunbils]] of [[Zabulistan]], seizing [[Lashkar Gah|Bust]] and a few cities in [[Zabulistan]].{{sfn|Zarrinkub|1975|p=24}}{{sfn|Marshak|Negmatov|1996|p=450}}

===Conquest of Iranian Azerbaijan===
[[File:Derbent winter.jpg|thumb|left|Sassanid fortress in [[Derbent]], present day [[Dagestan]], [[Russia]]. It fell to the Muslims in 643.]]

The conquest of [[Iranian Azerbaijan]] started in 651,<ref>Pourshariati (2008), p. 468</ref> part of a simultaneous attack launched against Kerman and Makran in the southeast (described above), against Sistan in the northeast and against Azerbaijan in the northwest. Hudheifa ibn Al Yaman was assigned Azerbaijan. Hudheifa marched from Rey in central Persia to [[Zanjan, Iran|Zanjan]], a well-fortified Persian stronghold in the north. The Persians came out of the city and gave battle, but Hudheifa defeated them, captured the city, and those who sought peace were granted it on the usual ''[[jizya]]'' conditions.<ref name="autogenerated4">{{cite book|title=The Muslim Conquest of Persia|first= A.I. |last=Akram|chapter=15|isbn= 978-0-19-597713-4|year= 1975 }}</ref> From Zanjan, Hudheifa marched to [[Ardabil]] which surrendered peacefully. Hudheifa then continued his march north along the western coast of the [[Caspian Sea]] and captured [[Bab al-Abwab]] by force.<ref name="autogenerated2"/> At this point Hudheifa was recalled by [[Uthman]], to be replaced by [[Bukair ibn Abdullah]] and Utba ibn Farqad. They were sent to carry out a two-pronged attack against Azerbaijan: Bukair along the western coast of the Caspian Sea, and Uthba into the heart of Azerbaijan. On his way north Bukair was halted by a large Persian force under [[Isfandiyar (Sasanian commander)|Isfandiyar]], the son of [[Farrukhzad]]. A pitched battle was fought, after which Isfandiyar was defeated and captured. In return for his life, he agreed to surrender his estates in Azerbaijan and persuade others to submit to Muslim rule.<ref name="Al-Tabari 1993"/> Uthba ibn Farqad then defeated Bahram, brother of Isfandiyar. He too sued for peace. Azerbaijan then surrendered to Caliph Umar, agreeing to pay the annual ''jizya''.

===Conquest of Eastern Armenia===
[[File:Tbilisi (20).jpg|thumb|View of Tbilisi, which fell to the Rashidun Caliphate in 644.]]

The Muslims had conquered [[Byzantine Armenia]] in 638–639. [[Sassanid Armenia]], remained in Iranian hands, along with [[Greater Khorasan|Khorasan]]. Umar refused to take any chances; he did not consider the Persians weak, which facilitated the speedy conquest of the Persian Empire. Again Umar sent simultaneous expeditions to the far north-east and north-west of the Persian Empire, one to [[Greater Khorasan|Khurasan]] in late 643 and the other to [[Sasanian Armenia|Armenia]].
[[Bukair ibn Abdullah]] was ordered to capture [[Tiflis]]. From Bab, on the western coast of the Caspian Sea, Bukair continued his march north. Umar employed his traditional successful strategy of multi-pronged attacks. While Bukair was still kilometres away from [[Tiflis]], Umar instructed him to divide his army into three corps. Umar appointed Habib ibn Muslaima to capture Tiflis, Abdulrehman to march north against the mountains and Hudheifa to march against the southern mountains. With the success of all three missions, the advance into Armenia came to an end with the death of Umar in November 644. By then almost the whole of the South [[Caucasus]] was captured.<ref>The Muslim Conquest of Persia By A.I. Akram. Ch:16 {{ISBN|978-0-19-597713-4}},</ref>

==Conquest of Khorasan==
[[File:Ancient Khorasan highlighted.jpg|thumb]]
{{Main|Muslim conquest of Khorasan}}
{{Further|Islamic conquest of Turkestan|Islamic conquest of Afghanistan|History of Arabs in Afghanistan}}

Khorasan was the second-largest province of the Sasanian Empire. It stretched from what is now northeastern Iran, northwestern Afghanistan and southern Turkmenistan. In 651 the conquest of Khurasan was assigned to [[Ahnaf ibn Qais]].<ref name="autogenerated2"/> Ahnaf marched from [[Kufa]] and took a short and less frequented route via [[Rey, Iran|Rey]] and [[Nishapur]]. Rey was already in Muslim hands and Nishapur surrendered without resistance. From Nishapur, Ahnaf marched to [[Herat]] in western Afghanistan. Herat was a fortified town, and the [[Siege of Herat (651)|resulting siege]] lasted for a few months before it surrendered, bringing the whole of southern Khorasan under Muslim control. Ahnaf then marched north directly to [[Merv]], in present-day [[Turkmenistan]].<ref>The Muslim Conquest of Persia By A.I. Akram. Ch:17 {{ISBN|978-0-19-597713-4}},</ref> Merv was the capital of Khurasan and here Yazdegred III held his court. On hearing of the Muslim advance, Yazdegerd III left for [[Balkh]]. No resistance was offered at Merv, and the Muslims occupied the capital of Khurasan without a fight. Ahnaf stayed at Merv and waited for reinforcement from Kufa. Meanwhile, Yazdegerd had also gathered considerable power at Balkh and allied with the Turkic Khan of [[Farghana]], who personally led the relief contingent. Umar ordered Ahnaf to break up the alliance. The Khan of Farghana, realizing that fighting against the Muslims might endanger his own kingdom, withdrew from the alliance and pulled back to Farghana. The remainder of Yazdegerd's army was defeated at the [[Battle of Oxus River]] and retreated across the [[Oxus]] to [[Transoxiana]]. Yazdegerd himself narrowly escaped to [[Tang dynasty|China]].The Muslims had now reached the outermost frontiers of Persia. Beyond that lay the lands of the [[Turkic peoples|Turks]] and still further lay China. Ahnaf returned to Merv and sent a detailed report of his success to the anxiously waiting Umar, and sought permission to cross the Oxus river and invade Transoxiana. Umar ordered Ahnaf to stand down and instead consolidate his power south of the Oxus.

==Sasanian rebellion==
{{Main|Persian revolts against the Rashidun Caliphate}}

Umar was assassinated in November 644 by an Iranian slave named [[Abu Lu'lu'a Firuz]] – in some narrations a former Sasanian solidarity soldier – after Umar allegedly refused to lift a tax imposed upon the latter. Soon after, Abu Lu'lu'a's was either executed or committed suicide.<ref>{{cite encyclopedia|last1=Pellat|first1=Charles|author1-link=Charles Pellat|date=2011|title=Abū Loʾloʾa|encyclopedia=Encyclopaedia Iranica|editor1-last=Yarshater|editor1-first=Ehsan|editor1-link=Ehsan Yarshater|url=https://iranicaonline.org/articles/abu-loloa-a-persian-slave-of-mogira-b}}</ref> The incident spurred [[Ubayd Allah ibn Umar|Ubayd Allah]], one of Umar's sons, to also kill [[Hurmuzān]], an ex-[[Sasanian]] military officer who had been working for Umar as an adviser after his capture – acting upon a claim that Hurmuzan had been seen conspiring with Abu Lu'lu'a while he was holding the murder weapon.<ref>{{harvnb|Madelung|1997|p=69}} (cf. p. 404, where Madelung refers to him as "Jufayna al-Naṣrānī").</ref>

[[Uthman ibn Affan]] (644–656) succeeded Umar as caliph. During his reign, almost the whole of the former Sassanid empire's territory rebelled from time to time, requiring him to send several military expeditions to crush the rebellions and recapture Persia and its vassal states. The main rebellions were in the Persian provinces of [[Sasanian Armenia|Armenia]], [[Azerbaijan (Iran)|Azerbaijan]], [[Fars province|Fars]], [[Sakastan (Sasanian province)|Sistan]] (in 649), [[Greater Khorasan|Khorasan]] (651), and [[Makran]] (650).<ref>{{Cite book |last=A. I. Akram |url=http://archive.org/details/TheMuslimConquestOfPersia |title=The Muslim Conquest of Persia |date=2018-04-19 |isbn=978-0-19-597713-4 |pages=288 |author-link=Agha Ibrahim Akram}}</ref> Finally, in 651, [[Yazdegerd III]], the last Sassanid emperor, was killed near [[Merv]] by a local miller for his purse,<ref>{{cite encyclopedia | url=http://p2.www.britannica.com/oscar/print?articleId=106324&fullArticle=true&tocId=9106324 | title=Iran | encyclopedia=[[Encyclopædia Britannica]] | access-date=7 January 2007 | archive-date=13 August 2013 | archive-url=https://web.archive.org/web/20130813184232/http://p2.www.britannica.com/oscar/print?articleId=106324&fullArticle=true&tocId=9106324 | url-status=live }}</ref> thus putting an end to both his dynasty and to organized Persian resistance. Meanwhile, Uthman's empire expanded beyond the borders of the Sasanian Empire, to [[Transoxiana]], [[Balochistan (region)|Baluchistan]], and the [[Caucasus]]. For many decades to come, this was the easternmost limit of Muslim rule.

==Persia under Muslim rule==

{{See also|Islamization of Iran|Islam in Iran}}

===Administration===
[[File:Islamic coin, Time of the Rashidun. Khosrau type. AH 31-41 AD 651-661.jpg|thumb|upright=1.15|Coin of the [[Rashidun Caliphate]]. Imitation of [[Sasanid Empire]] ruler [[Khosrau II]] type. BYS ([[Bishapur]]) mint. Dated YE 25 = AH 36 (AD 656). Sasanian style bust imitating [[Khosrau II]] right; [[Basmala|bismillah]] in margin/ Fire altar with ribbons and attendants; star and crescent flanking flames; date to left, mint name to right.]]

Under Umar and his immediate successors, the Arab conquerors attempted to maintain their political and cultural cohesion despite the attractions of the civilizations they had conquered. The Arabs initially settled in the garrison towns rather than on scattered estates.

The new non-Muslim subjects were tolerated by the state and known as ''[[dhimmi]]'' (''protected''), and were to pay a special tax, the [[jizya]] (''tribute''), which was calculated at varying individual rates, usually two [[dirham]]s for able-bodied men of military age, in return for exemption from military service. Women and children were exempted from the jizya.<ref>{{cite book
| author = Kennedy, Hugh
| title = The Prophet and the Age of the Caliphates
| publisher = Longman
| year = 2004
| page = 68
| author-link = Hugh N. Kennedy
}}</ref>
Mass conversions were neither desired nor allowed, at least in the first few centuries of Arab rule.<ref>{{cite book | author-link=Richard Nelson Frye | last=Frye | first=R.N | title=The Golden Age of Persia | year=1975 | isbn=978-1-84212-011-8 | page=62| publisher=Phoenix Press }}</ref><ref>[[Tabari]]. Series I. pp. 2778–9.</ref><ref name=boyce>Boyce, Mary (1979), Zoroastrians: Their Religious Beliefs and Practices, London: Routledge, {{ISBN|978-0-415-23903-5}} pg.150</ref>

Umar is reported to have issued the following instructions about the unconverted people: "Make it easy for him, who can not pay tribute; help him who is weak, let them keep their titles, but do not give them our [[kuniyat]] [''Arabic traditional nicknames or titles'']."<ref name="Their Non-Muslim Subjects pg.138">''The Caliphs and Their Non-Muslim Subjects''. By A. S. Tritton, pg.138.</ref>
Umar's liberal policies were continued by at least his immediate successors. In his dying charge to Uthman, he is reported to have said, "I charge the caliph after me to be kind to the dhimmis, to keep their covenant, to protect them and not to burden them over their strength."<ref name="Their Non-Muslim Subjects pg.138"/>
As a matter of practicality, the jizya replaced the Sasanian poll taxes, which tended to be much higher than the jizya. In addition to the jizya, the old Sasanian ''land tax'' (known in Arabic as ''Kharaj'') was also adopted. Umar is said to have occasionally set up commissions to survey tax burdens in order to ensure that they wouldn't be more than the land could bear.<ref>''The Caliphs and Their Non-Muslim Subjects''. By A. S. Tritton, pg.139.</ref> It is reported that Zoroastrians were subjected to humiliation and ridicule when paying the [[jizya]] in order to make them feel inferior.{{sfn|Boyce|2001|p=146}}

At least under the Rashiduns and early Umayyads, the administrative system of the late Sasanian period was largely retained: a pyramidal system where each quarter of the state was divided into provinces, the provinces into districts, and the districts into sub-districts.  Provinces were called ''ustan'' (Middle Persian ''ostan''), and the districts ''shahrs'', centered upon a district capital known as a ''shahristan''. The subdistricts were called ''tasok'' in Middle Persian, which was adopted into Arabic as ''tassuj'' (plural ''tasasij'').{{Citation needed|date=April 2024}}

===Religion===
{{See also|Islamization of Iran|Persecution of Zoroastrians|Islamic Missionary Activity}}

Zoroastrians were made to pay an extra tax called [[jizya]], or be killed, [[Slavery in the Rashidun Caliphate|enslaved]] or imprisoned. Those paying jizya were subjected to insults and humiliation by the tax collectors.<ref name="boy148">{{harvnb|Boyce|2001|p=148}}</ref><ref name="ann205">{{harvnb|Lambton|1981|p=205}}</ref><ref name=mb878 >{{harvnb|Meri|Bacharach|2006|p=878}}</ref> Zoroastrians who were captured as slaves in wars were given their freedom if they converted to Islam.<ref name="boy148" /><ref name="fez">{{cite web|url=http://zoreled.org/historyzorislamiciran.aspx |title=History of Zoroastrians in Islamic Iran |work=FEZANA Religious Education |access-date=20 October 2009 |url-status = dead|archive-url=https://web.archive.org/web/20080505090009/http://zoreled.org/historyzorislamiciran.aspx |archive-date=5 May 2008 }}</ref> While giving freedom of choice, the [[Arabs|Arab]] conquerors designated privileges for those who converted to Islam and in theory gave them rights equal to Arab muslims.<ref>The Cambridge History of Iran Volume4 The Period from the Arab Invasion to the Saljuqs, p. 483</ref><ref>{{Cite book |title=History of Civilizations of Central Asia |publisher=UNESCO |year=2006 |isbn=978-9231032110 |pages=464}}</ref> These privileges included exemption from Jizya.<ref>{{Cite book |title=History of Civilizations of Central Asia |publisher=UNESCO |year=2006 |isbn=978-9231032110 |pages=464}}</ref> The conversion process was slow and uncompleted, stretching over many centuries, with a majority of Persians still following Zoroastrianism at the turn of the millennium.<ref>{{Cite web|url=https://iranicaonline.org/articles/fars-iii|title=FĀRS iii. History in the Islamic Period – Encyclopaedia Iranica|website=iranicaonline.org|access-date=24 September 2020|archive-date=18 November 2020|archive-url=https://web.archive.org/web/20201118150626/https://iranicaonline.org/articles/fars-iii|url-status=live}}</ref><ref>{{Cite book |title=History of Civilizations of Central Asia |publisher=UNESCO |year=2006 |isbn=978-9231032110 |pages=464}}</ref>

[[Muslim]] leaders in their effort to win converts encouraged attendance at Muslim prayer with promises of money and allowed the [[Quran]] to be recited in [[Persian language|Persian]] instead of Arabic so that it would be intelligible to all.<ref name="Arnold" /> Islam was readily accepted by [[Zoroastrians]] who were employed in industrial and artisan positions because, according to Zoroastrian dogma, such occupations that involved defiling fire made them impure.<ref name="Arnold">The preaching of Islam: a history of the propagation of the Muslim faith By Sir [[Thomas Walker Arnold]], pg.170–180</ref> Moreover, Muslim missionaries did not encounter difficulty in explaining Islamic tenets to Zoroastrians, as there were many similarities between the faiths. According to [[Thomas Walker Arnold]], the Persian would meet [[Ahura Mazda]] and [[Ahriman]] under the names of [[Allah]] and [[Iblis]].<ref name="Arnold" /> In [[Afghanistan]], Islam was spread due to [[Umayyad]] missionary efforts particularly under the reigns of [[Hisham ibn Abd al-Malik]] and [[Umar ibn Abd al-Aziz]].<ref name="Arnold" />

There were also large and thriving [[Christians|Christian]] and [[Jews|Jewish]] communities, along with smaller numbers of [[Buddhist]]s and other groups. The population moved slowly and steadily toward [[Islam]]. The nobility and citizens converted first. Islam spread more slowly among the peasantry and the ''[[dihqan]]s'', or landed gentry. By the late 10th century, the majority of the Persians had become Muslim.

Until the 15th century, most Persian Muslims were [[Sunni Islam|Sunni Muslims]] of the [[Shafi'i]]<ref>{{Cite book |last=Lombard |first=Maurice |url=https://books.google.com/books?id=cNG8MKDPVUMC&dq=safavid+persia+conversion&pg=PR14 |title=The Golden Age of Islam |date=2004 |publisher=Markus Wiener Publishers |isbn=978-1-55876-322-7 |language=en}}</ref> and [[Hanafi]] legal schools, with the rise of the [[Safavid]]s in the early 16th century and their [[Safavid conversion of Iran to Shia Islam|forced conversion of Sunnis]], Shi'a Islam came to dominate the land.

==Language of Persia==
During the [[Rashidun Caliphate]], the official language of Persia (including Mesopotamia) remained [[Middle Persian|Middle Persian (Pahlavi)]], just as the official languages of [[Bilad al-Sham|Syria]] and [[Lower Egypt|Egypt]] remained [[Greek language|Greek]], both languages came to the region through the conquering Greek Macedonian and Persian Achaemenid empires. During the [[Umayyad Caliphate]], the Umayyads made [[Arabic]] the primary language of their subjected people throughout their empire. Particularly, [[Al-Hajjaj ibn Yusuf]] (661–714) officially changed the administrative language of Iraq from Middle Persian (Pahlavi) to Arabic, this was the first since the [[Neo-Babylonian Empire]] that a Semitic language was reinstated as an official language in Mesopotamia ([[Iraq]]). Arabic mainly supplanted other [[Afroasiatic languages|Afro-Asiatic]] [[sister language]]s, like [[Coptic language|Coptic]] in Egypt and [[Berber languages|Berber]] and [[Punic language|Punic]] in the [[Maghreb]] region (Berber is still spoken and official in Algeria and Morocco), but the more distant [[Indo-European languages|Indo-European]] languages like Middle Persian and Kurdish proved to be more enduring. Most of Middle Persian structure and vocabulary survived, evolving into [[Persian language|New Persian]]. Persian incorporated a certain amount of Arabic vocabulary, especially words pertaining to religion (and later to science and arts), and it switched from the [[Pahlavi scripts]] to a [[Perso-Arabic alphabet|modified version of the Arabic alphabet]].<ref>{{cite web|url=http://www.languages.umd.edu/persian/persianlanguage1.php |title=What is Persian? |publisher=The center for Persian studies |url-status = dead|archive-url=https://web.archive.org/web/20051210024444/http://www.languages.umd.edu/persian/persianlanguage1.php |archive-date=10 December 2005 }}</ref> Today Persian is spoken officially in [[Iran]], [[Afghanistan]], and [[Tajikistan]].

==Urbanisation==
The Arab conquest of Persia led to a period of extreme [[urbanisation]] in Iran, starting with the ascension of the [[Abbasids|Abbasid]] dynasty and ending in the 11th century CE.<ref name="youtube.com">{{YouTube|C0i7MMO0orE|Professor R. Bulliet on Iran's urbanisation (1h 10m 29s)}}</ref> This was particularly true for the eastern parts of the country, for regions like [[Greater Khorasan|Khorasan]] and [[Transoxiana]].<ref>{{cite book|url=https://books.google.com/books?id=uQ7k2vQlYxEC&pg=PA50|title=Al-Hind: The Slavic Kings and the Islamic conquest, 11th–13th centuries|via=google.nl|isbn=0391041746|last1=Wink|first1=André|year=2002|publisher=BRILL |access-date=19 October 2015|archive-date=10 April 2023|archive-url=https://web.archive.org/web/20230410122239/https://books.google.com/books?id=uQ7k2vQlYxEC&pg=PA50|url-status=live}}</ref> During this period, Iran saw the development of massive metropolises, some reaching population numbers of up to 200,000 people.<ref name="youtube.com"/> This period of extreme urbanisation was followed in the late 11th and early 12th century by a collapse of the Iranian economy, which led to large scale emigrations of Iranians into Central Asia, India, the rest of the Middle East, and Anatolia. This catastrophe has been cited by some as reason for the Persian language becoming widespread throughout Central Asia and large parts of the Middle East.<ref>{{YouTube|C0i7MMO0orE|Professor R. Bulliet on Iran's urbanisation (1h 11m 48s)}}</ref>

==See also==
{{Columns-list|colwidth=30em|
* [[Arab-Byzantine Wars]]
* [[Arab rule in Georgia]]
* [[Islamic conquest of Afghanistan]]
* [[Islamization of Iran]]
* [[Military history of Iran]]
* [[Safavid conversion of Iran to Shia Islam]]
* [[Muslim conquest of Transoxiana]]
* [[Spread of Islam]]
* [[History of Iran after Islam]]
* [[Iran during the Caliphate]] 
* [[Ali's Eastern Campaigns]]
}}

==References==
{{Reflist}}

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* {{cite book |last=Gazerani |first=Saghi  |title=The Sistani Cycle of Epics and Iran's National History: On the Margins of Historiography |year=2015 |publisher=BRILL|pages=1–250 |isbn=9789004282964 |url=https://books.google.com/books?id=92zsCgAAQBAJ&q=false}}
*{{cite book |last1=Greatrex |first1=Geoffrey |last2=Lieu |first2=Samuel N. C. |title=The Roman Eastern Frontier and the Persian Wars (Part II, 363–630 AD) |location=New York, New York and London, United Kingdom |publisher=Routledge (Taylor & Francis) |year=2002 |isbn=0-415-14687-9 |url=https://books.google.com/books?id=zc8iAQAAIAAJ}}
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* {{cite encyclopedia |last=A. K. S. |first=Lambton  |article=FĀRS iii. History in the Islamic Period|url=http://www.iranicaonline.org/articles/fars-iii |encyclopedia=Encyclopaedia Iranica, Vol. IX, Fasc. 4 |pages=337–341 |year=1999 |ref={{harvid|Lambton|1981}}}}
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*{{cite book |last1=Marshak |first1=B.I. |first2=N.N. |last2=Negmatov |chapter=Sogdiana |title=History of Civilizations of Central Asia, Volume III: The Crossroads of Civilizations: A.D. 250 to 750 |editor=B.A. Litvinsky, Zhang Guang-da and R. Shabani Samghabadi |year=1996 |publisher=UNESCO |isbn=92-3-103211-9}}
* {{Citation |last1=Meri |first1=Josef W. |last2=Bacharach |first2=Jere L. |title=Medieval Islamic Civilization: L-Z, index |series=Medieval Islamic Civilization: An Encyclopedia |publisher=Taylor & Francis |year=2006 |edition=illustrated |volume=II |pages=878 |url=https://books.google.com/books?id=LaV-IGZ8VKIC&pg=PP1 |isbn=9780415966924}}
* {{cite encyclopedia |last=Morony |first=M. |author-link=Michael G. Morony |encyclopedia=[[Encyclopaedia Iranica]] |title=Arab Conquest of Iran |url=http://www.iranicaonline.org/articles/arab-ii |year=1987 |volume=2, ANĀMAKA – ĀṮĀR AL-WOZARĀʾ }}
* {{cite encyclopedia |last=Morony |first=M.  |article=ʿARAB ii. Arab conquest of Iran|url=http://www.iranicaonline.org/articles/arab-ii |encyclopedia=Encyclopaedia Iranica, Vol. II, Fasc. 2 |pages=203–210 |year=1986 }}
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*{{cite book |last=Pourshariati |first=Parvaneh |title=Decline and Fall of the Sasanian Empire: The Sasanian-Parthian Confederacy and the Arab Conquest of Iran |location=London and New York |publisher=I.B. Tauris |year=2008 |isbn=978-1-84511-645-3 |url=https://books.google.com/books?id=I-xtAAAAMAAJ}}
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*{{cite encyclopedia |last=Shapur Shahbazi |first=A. |title=SASANIAN DYNASTY |url=http://www.iranicaonline.org/articles/sasanian-dynasty |year=2005 |encyclopedia=Encyclopaedia Iranica, Online Edition |access-date=3 April 2014}}
* {{cite book |last=Sicker |first=Martin  |title=The Islamic World in Ascendancy: From the Arab Conquests to the Siege of Vienna|author-link=Martin Sicker |year=2000 |publisher=Praeger |isbn=978-0-275-96892-2 }}
* {{cite book |last1=Spuler |first1=Bertold |author-link1=Bertold Spuler |title=Persian Historiography and Geography: Bertold Spuler on Major Works Produced in Iran, the Caucasus, Central Asia, India and Early Ottoman Turkey |translator-first1=M. Ismail |translator-last1=[[M. Ismail Marcinkowski]]  |others=[[Clifford Edmund Bosworth]] (foreword) |year=2003 |publisher=Pustaka Nasional |location=Singapore |isbn=978-9971-77-488-2 }}
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* {{cite book |last=Zarrin'kub |first=Abd al-Husayn  |title=Ruzgaran: tarikh-i Iran az aghz ta saqut saltnat Pahlvi|author-link=Abdolhossein Zarinkoob |year=1999 |publisher=Sukhan |isbn=978-964-6961-11-1 }}
* {{cite book |last=Zarrinkub |first=Abd al-Husain  |title=The Cambridge History of Iran, Volume 4: From the Arab Invasion to the Saljuqs |year=1975 |publisher=Cambridge University Press |location=Cambridge|chapter=The Arab conquest of Iran and its aftermath |pages=1–57 |isbn=978-0-521-20093-6 |url=https://books.google.com/books?id=hvx9jq_2L3EC}}

==Further reading==
{{refbegin}}
*{{cite book |last=Litvinsky |first=B. A. |chapter=The Arab Conquest, Part One: The Arab Conquest of Iran | pages = 449–456 |year=1996 | editor-first1 = B. A. | editor-last1 = Litvinsky | editor-first2 = Guang-da | editor-last2 = Zhang | editor-first3 = R. Shabani | editor-last3 = Samghabadi | title = History of Civilizations of Central Asia, Volume III: The Crossroads of Civilizations, A.D. 250 to 750 | location = Paris |publisher = UNESCO Publishing |isbn = 92-3-103211-9 | url = {{Gbooks|883OZBe2sMYC|plainurl=yes}} }}
{{refend}}

==External links==
{{Wikiquote}}

{{Sasanian Empire}}
{{Ancient Iranian wars}}
{{Ancient Mesopotamia topics}}
{{Iran topics}}

[[Category:Muslim conquest of Persia| ]]
[[Category:Fall of the Sasanian Empire| ]]
[[Category:Invasions of Iran]]
[[Category:7th century in Iran]]
[[Category:Dissolutions of empires|Sasanian]]
[[Category:Book burnings]]
[[Category:Destroyed libraries]]
[[Category:Early Muslim conquests]]