The Arab race had been vassals of the Persians for over 3000 years. Through the reign of all the great Persian Zoroastrian empires.
The Persians have always seen the Arabs as an inferior race. One to be tolerated and ruled over. A race of sand dwelling barbarians who they commonly abuse as lizard eaters and daughter killers.
The Arabs were pre-Islam never hated by the Persians. Only looked down on. The Persians saw only the Greeks and the Roman empires as their equal and military competition to the dominion over the civilized world stretching from Asia to Europe and extending to parts of Russia and China.
The Persians always had a hands off policy with their Aryan correligionists in India. The Indus forming the unspoken cleave line between the two civilizations.
Zoroastrianism (Mazdayasniism - and Mithraism and Magiism and Manicheism) was the spiritual monotheistic precusrsor, the first message to the first prophet to and from his chosen people, in the ancient world.
It colored and widely impacted on Judaiism and Christianity and finally Islam. The core tenets remaining the same and unchanged.
Where the faiths diverged and so did the individual Books was the tribe and people specific lore and life in those times. Essentially, Islam came to the Arabs last. And the Quran was the Avesta (and the Torah and the Bible after it) written in Arabic lore, and tribal code.
Islam was always a political movement. An imperialistic movement of Arab rise and finally their day in the sun.
If Al Qadissiyah had gone the other way, Zoroastrianism (more powerful than Christianity for over 500 years of the Roman empire) would have been the dominant religion in the world today. And Islam would have remained a local Arab belief system. Or an Arab cult.
But the boy king leading a weakened empire fatigued by over 2000 years of continuous war, lost. And the Arab hordes sacked Persia.
The Persians though did not go down without a fight and pockets of resistance through the land fought on under feudal rulers and satraps for the next 300 years.
However, the empire was finished. The emperor assassinated. His sons fled into exile to hold a titular Persian throne and court in distant China. From where they plotted a return. That never happened.
Many of the Persian elite seeing the writing on the wall made deals with the Arabs and other satraps, as vicious infighting ensued in the dying throes of the Persian empire. They converted to Islam and jockeyed for power in the new scheme of things.
Things became increasingly difficult for the Zoroastrians and their temples were defiled, their fires spat into. Back breaking taxes and the sword for worshiping Ahura Mazda and not Allah. For following Persian Zarathushtra and not Arab Muhammad.
Increasingly, simultaneously, a power vacuum followed the death of Muhammad. And a power struggle ensued between the warring Arab elite and the Persian elite who were far far more sophisticated in matter of rule and politics and power dynamics and the control of hearts and minds of native and alien populaces on a global scale.
Essentially what happened from there was that increasingly Persians started becoming Muslim. Accepting Islam. And then remolding Islam into their ancestral belief system, insidiously, systematically, thoroughly, completely, to the point where Islam essentially became Zoroastrianism Part 2. Where Ahura Mazda was now called Allah. Where Zarathushtra was now called Muhammad. Where the Avesta gave way to the Quran - but their Quran. And thence followed the writing of the Hadith.
It is a known fact that to a man, almost all the clerics and writers of those times, were Persian. Not Arab. Theirs is the narrative that got pushed. That endured. That got propagated over the next 1300 years of Islam around the world.And softened the blow for the common Persians when after 300 years of struggle Persia finally "converted" completely by 1000 AD.
And therein lies the irony. Islam in its moment of greatest triumph, also seeded its permanent internal split and war.
And the Middle East and the Muslim world will always have the mirage of Peace till Persia finally reclaims herself and reverts to her original faith. And the mother faith of all monotheist major faiths of the world.
It is a huge soul numbing and mental crunch for the Persians vis a vis the Arabs. Who they hate. But love Muhammad. To having to write in the Arabic script when the Persian one was one of the world's oldest. Of praying in Arabic and not their ancestral Avestan.
All this while they continue to fight the Arabs for control of their former empire minion states. And peoples. Once more.
Cheers, Doc