I've linked to these articles by Iranian historian
Khodadad Rezakhani before but they're maybe relevant for looking at the rise of early Islam from a Sasanian perspective.
The Arab Conquests and Sasanian Iran (Part 1) Some General Observations on the Late Sasanian PeriodThe Arab Conquests and Sasanian Iran (Part 2) Islam in a Sasanian ContextFrom a late antique point of view, alongside the Christian commonwealth, the Khurramdīniyya/Mazdakite religious movements might have been in the process of creating a socio-religious commonwealth.
In contrast, Zoroastrianism, the dominant state religion of the Sasanians, shows less interest in playing such a role. The common charge of a Zoroastrian religious autocracy, presided over by a dominant priestly establishment and headed by a mobedān mobed, is more of a mirage, and based on little evidence. Apart from the absence of a sort of “orthodox” or “mainline” Zoroastrian doctrine in the Sasanian world, there is little evidence of the presence of such dominant clergy.14 Additionally, late Sasanian Kings of Kings are known for making clear and public overtures to their native Christian communities. In fact, Khosrow II Aparwēz (591–628 CE), the quintessential late Sasanian king, married a Christian wife (perhaps two) and had a Christian chief minister. Likewise, in the course of mustering support for his campaigns against Byzantium, he supported the Eastern Christian community of the Sasanian domains; buttressed the Nestorians of Syria; and, upon conquering and entering Jerusalem, moved the True Cross from Jerusalem to Khūzestān in order to provide much prestige for the Christians of his empire. A theocratic, dominant Zoroastrian religious structure, if it existed, would simply not have allowed the king to have open relations with members of another religion, let alone to promote their interests.
Christians, in fact, were the dominant population in the western regions of the Sasanian realm in this time period. Aramaic-speaking Christians and Jews were the main population of Mesopotamia, the heart of the Sasanian Empire (Middle Persian dil-i Ērānshahr). South-western Mesopotamia was the realm of the Arab kingdom of Ḥīra, the land of the Lakhmids, who ruled the Arab tribes of northern Arabia on behalf of the Sasanians. Eastern Arabia was also populated by Arabic-speaking tribes who were controlled via the Sasanian administration of Baḥrayn, including all of Eastern Arabia down to Oman. Southern Arabia, the former kingdom of Ḥimyar, had become part of the Sasanian Empire following its conquest about 570 CE in wars against the Axumites.15
In this environment, Khosrow II invaded Syria in 602 and defeated the Byzantine armies there. Soon, all of Syria, Palestine, and most of Anatolia had fallen into Sasanian hands. By 615, Egypt was also a Sasanian territory. For over two decades, a whole generation in fact, the Sasanians were masters of all of West Asia, and by having defeated the Hephthalites with the help of the Western Turks in the 560s, they were also in secure control of much of their lost territory in East Iran. When the prophet of Islam was migrating from Mecca to Medina to establish his religious state there, he was living in a world dominated by Sasanian power. The state that he went on to found, and which came to dominate the Sasanian territories, should not be seen as an element external to the Sasanian Empire that caused its “fall.” Rather, we can view the nascent Islamic state as an element internal to the Sasanian order that lent itself to furthering change that was already well underway, as will be discussed in the second part of this essay.
It was in the context of a West Asian world dominated by the Sasanians that Islam began as a political and religious movement in Arabia Deserta. Islamic beliefs were highly influenced by Syriac Christianity, including heterodox forms of that faith – so much so that in retelling many of the devotional stories shared with the Christian faith, the Qur’an in fact alludes to and adapts narratives not included in the canonical scriptures of the major churches. Far from the simple Bedouins disconnected from the world that they are often imagined to be, the Arabs of the Ḥijāz in fact lived fully in contact with, and indeed as an integral part of, the world of Late Antiquity. They were well aware of the Sasanian-Axumite conflicts in Yemen, and knew about the Byzantine defeat and withdrawal from Syria and Egypt. The prophet of Islam, Muhammad, fits well within the pattern of the rise of the Holy Man in Late Antiquity, during which time we see an increasing trend towards, or obsession with, the concept of prophethood and the primacy of revealed scripture. Muhammad was not by any means the only Arabian prophet preaching a version of a “pure” Abrahamic religion, one “untainted” by Rabbinic Judaism or Christianity, in Arabia. The recurring theme of the prophet or holy man disappearing into the desert to contemplate and ponder, reflected in the life of the original Christian monk, St. Anthony the Great, is a blueprint for that of Muhammad. Arab prophets, who are even mentioned in Islamic texts, were a common feature in this society, and a focal point for social movements that wanted to break the geographical and political stranglehold imposed by the state of war dominating the region since the early sixth century.1
Accustomed to open trade with Roman Syria (perhaps as leather merchants) and easy access to the Red Sea and Indian Ocean trade, the Arabs of the Ḥijāz were now bound by a Sasanian hegemony that stifled their ability to act.2 The Sasanians even controlled Najrān, close to the border between Ḥimyarite Yemen and the Ḥijāz, which was the main point of contact for the people of Mecca and Yathrib (later Medina) with the resources of Ḥimyarite Yemen. With the Kingdom of Ḥimyar gone and the Syrian trade interrupted by the Sasanian-Byzantine wars, the sources of the relative prosperity of the Bedouin and their trade city of Mecca vanished. The Sasanians, following their control of Jidda and interruption of Byzantine-Axumite contacts, even tried to impose a ruler on Mecca, although this was unsuccessful.3 It is no surprise that the first foreign relations overture of the new community of Muslims as it sought allies was with the Axumite king, the Negus (Ar. Najjāshī).
The conquered population of Mesopotamia, largely Christian or Jewish and speaking Aramaic, saw no reason to adopt the religion of the newcomers. The newcomers themselves probably had little idea of the differences between their own religion and those of the conquered. Both groups believed in one god, both prayed in largely the same way, and both idealized the same prophets and patriarchs of Israel: Abraham, Joseph, Moses, David, Solomon, and even Jesus.
As the administration matured, however, so did the ideology of the newcomers. The four Rāshidūn caliphs gave way to the Umayyad imperial administration, and like all imperial systems, the Umayyads saw the necessity to adopt a clear ideology.10 Arabism or Arab tribalism was the most obvious choice, and the Umayyads adopted it wholeheartedly. But there were also the increasing benefits to the newcomers of defining their religion. In the late antique world of universal religions, clarifying your beliefs and making it the official ideology of your nascent empire had many benefits, including the ability to tax those who did not fit your definition squarely.
In this system, access to power meant two things: adopting Arabism and adopting the religion. Among the second and third generation of the newcomers, mounting your horse and conquering had less attraction than entering the administration to run what was already conquered by your parents. Arab tribalism and adherence to a particular ideology (i.e. Islam) became the main doors of access to power.
Not everyone accepted this, however, and much resistance came from within Muslim society itself. Certain factions rejected Arabism and tribalism, the explicit causes of trouble that had immediately followed the initial successes which had come through the conquests. Instead, they suggested that ideology should be the only way of accessing power, and no tribal affiliation should be put at equal footing with accepting the ideology. Belonging to the community of Muslims should be the only way of gaining full membership of the society. This, the ideology that was seen as the pure message of Islam, of course, was appealing to many, and became popular among many former Sasanian elites who already were outsiders in their own land. Speakers of Middle Persian, on its way to becoming New Persian since the sixth century, the Sasanian elite were already a minority among the majority Aramaic speakers. Becoming a minority of elites among a majority of Muslim Arabic speakers was hardly a shock to them.
As an educated class, these Sasanian elites quickly adopted the new ideology and gained positions of authority. Many of them became early interpreters of the canonical beliefs of the new religion, and emerged as insiders among the community of newcomers. They promoted the choice of religious adherence as the preferred marker of social membership, and alongside Arabic, fitted Persian, their spoken tongue, as the acceptable second language of Islam. Some of them, children of the conquered grandees of the Sasanian administration, became the religious authorities of the new community, using Arabic and Persian side by side to convert the rest of the population. The Sasanian elite, by accepting new socio-political realities and integrating their own culture into it, in fact remained dominant in the same territories, while accommodating a new Arab elite settling in the same area.
These were the actual vehicles of conversion in most of the former Sasanian Empire. Moving alongside the conquering armies and as part of the expanding administration, they used their own version of Persian, the vulgar, almost pidgin, spoken form of the language, instead of the high literate Middle Persian of the Sasanian administration and culture, to spread the new ideology. Just as in Syria, where speaking Arabic and adopting the new ideology, Islam, had become the way to access power, in the former Sasanian territories, speaking Persian and adopting the new ideology became the main way to gain similar power.
Topic: Qur'anic studies today