With the Arab victory over the Iranian forces at Nihavand in 641–642 c.e., referred to by the Arabs as the "Victory of Victories," the fall of the Sassanian Empire was final. The Sassanians had been a formidable power that had endured for four centuries, but in the end the corruption and greed of the ruling and priestly classes had left the imperial coffers depleted and, perhaps more importantly, eroded support among the empire's numerous heterodox subjects. Such internal problems hampered efforts to efficiently muster and deploy the impressive Iranian defenses. The ponderous Sassanian cavalry ultimately succumbed to the speedy attack and retreat tactics of the lightly armed Arab troops.
Fifteen years after Nihavand, most of the erstwhile Sassanian lands had come under Muslim control. Nevertheless, many of the fallen Iranian cities revolted and had to be reconquered several times. Even after the murder of the last Sassanian monarch, Yazdgard III, ended his flight from province to province from 651 to 652 c.e., parts of the population in various provinces continued to break their treaties of surrender to the Arabs and returned to their old religious practices and traditions. Particularly, changes of local governorship and the deaths of caliphs presented occasions for revolt, as was the case after the murders of ˓Umar, ˓Uthman, and ˓Ali.
In spite of this ongoing resistance and the polemics that were directed against the Arab conquerors—who were at times portrayed as devils and associates of Ahriman (the evil spirit in Zoroastrian belief)—a new landholding class eventually emerged, whose strength gradually increased through intermarriage with the indigenous residents.
The arrival of the new Arab overlords in Iran also brought with it a new religion. But the conversion of Iran to Islam was neither swift nor of a piece. Certain groups converted to Islam on a collective basis, but this was the exception rather than the rule. Some sections of the population opted for the jizya (tax levied on non-Muslims) and the kharaj (land tax), accepting the dhimmi status (a second-class-citizen status granting non-Muslims protection and limited religious freedom under Muslim rule) in order to hold on to their old ways. The privileges that came with conversion were, however, a decisive argument for many, especially those who had been disadvantaged by Zoroastrian religious organization and its rules. Artisans and craftsmen had been specifically affected in this way, as the Zoroastrian taboos regarding the pollution of the elements of fire, water, and earth clashed with many aspects of their professions, branding them unclean by association.
Ultimately, greater parts of the populace recognized some of the fundamental similarities between Islamic and Zoroastrian faith, which share the belief in one good god, one evil spirit or devil, a final judgment, and the notions of Paradise and Hell. Acceptance of the Islamic faith became more and more widespread. But even for those that held to the Zoroastrian faith, the restrictions imposed by the dhimmi status were less severe, and the privileges greater, than had been the case for Christians and Jews under Zoroastrian rule. During the Umayyad period, however, there was a marked increase in contempt and intolerance of Muslims toward Zoroastrian subjects, prompting a group of them to eventually emigrate to Gujarat, where their descendants, known as Parsees, practice their belief to this day.
It is noteworthy that adherents of non-Zoroastrian religions, or of groups that had been considered heretics by the Zoroastrian establishment in Sassanian times, enjoyed a distinctly greater amount of religious freedom under Muslim rule. The Sassanians had suppressed the heterodox groups existing in their empire, and to them the Islamic practice of giving dhimmi status to the "people of the Book" was tantamount to liberation.
The decline of Zoroastrianism in the face of the advent of Islam was by no means a rapid nor an altogether peaceful process. Interfaith strife and competition over local authority and resources persisted into Buyid times, and as late as the end of the tenth century an unsuccessful uprising of Zoroastrians took place in Shiraz. Although urban Zoroastrianism had declined at the close of the tenth century, attacks on Muslims on their way to worship were apparently still quite frequent in some provinces, and religious riots occurred constantly. The Muslims—Arabs as well as Iranian converts—usually emerged victorious from such confrontations due to their increasing numbers, bolstered both by conversion of Iranians as well as immigration of Arabs into Iran.
The rivalry between Zoroastrians and Muslims found expression not solely in riots and skirmishes. The two segments of the population also competed over economic assets, specifically the trade between China and Iran via Central Asia. On the other hand, some Arab immigrants joined existing trade networks, a cooperation that resulted in an increase of overland trade.
The degree of either cooperation or enmity between the two communities depended to a large extent on the way the conquest of each particular area or province had unfolded. The provinces in Iraq, Khuzistan, Azerbaijan, and Sistan, for example, had surrendered to the Arab invaders after comparatively few battles. In the absence of memories of prolonged and bloody conflict, amicable relations were more readily forged. In these areas, where Arabs and Iranians even stood together against outside aggressors like Turks and Mongols, the Muslim colonizers encountered a more fertile climate for their efforts toward religious conversion, which subsequently took place in a comparatively peaceful manner.
Urban strongholds central to Zoroastrian power, in which had to be conquered in protracted battles under immense bloodshed, were far less welcoming to the invaders, who in turn employed draconian measures to ensure their dominance. The resulting atmosphere in such locales was consequently characterized by mutual resentment, distrust, and general tension, a state of affairs that was ameliorated only with great hesitation. Finally, there were areas where hostility and active conflict persisted long after Arab settlements had been established. In the Transoxanian and Caspian regions, constant military confrontations between Iranian lords and Arab generals precluded coexistence, cooperation, and peaceful conversion longer than anywhere else in Iran. But ultimately, all efforts to oust the Arabs failed. The late Sassanian Empire had not fostered a society that stood united behind its ruling and priestly classes. After its fall, Zoroastrian leaders attempting to rally military opposition against the Arab conquest could summon neither the trust nor the support of the masses required for such undertakings.
Boyce, Mary. Zoroastrians: Their Religious Beliefs and Practices. London and Boston: Routledge & Kegan Paul, 1979.
Frye, Richard Nelson, ed. The Cambridge History of Iran, Vol. 4: The Period from the Arab Invasion to the Saljuqs. Cambridge, U.K.: Cambridge University Press, 1975.
Tabari, Abu Ja˒far Muhammad b. Jarir al-. The History of al-Tabari (Ta˒rikh al-rusul wa˒l-muluk), Vol. 14: The Conquest of Iran. Translated by G. Rex Smith. Albany: State University of New York Press, 1994.
Henning L. Bauer