Yazdegerd III Converts to Islam

Brainstorming POD ideas and one idea that comes to head is this. Prior to the Battle of Qadisiyyah the Muslim Caliph offered to the Persian Emperor to convert to Islam. At this time the opinion of the Caliphs was less on expansionism and was somewhat reluctant to invade Persia as a whole.

The battle itself took place after a previous invasion of Iraq by the Arabs that ha kicked out the Persians until a counter-attack by the Persians and Byzantine preparations for their own offensive forces the Islamic Arabs out.
Also to give context this is also after the disaster of Yarmouk that had crushed the Byzantines. Yazdegerd was also at this point coming out of very recently gaining control over Persia following the strife of the Byzantine-Sassanid wars. The only thing that held the two forces allied together was a recognition of the Arab threat and a marriage of Heraclius' daughter to the Persian Emperor.

What could have happened if Yazdegerd had converted or just agreed to pay the Jaziyah tax as a form of ransom (like the Byzantines did to the Persians for sometime).
 
I'm somewhat disinclined to trust the majority of sources for the seventh century conquests, given that almost everything we have is heavily influenced by the biases of the historians writing in the ninth century Abbasid court. There are no surviving contemporary Islamic accounts of what was really going on in the seventh century, and even Christian accounts, like Theophanes, suffer from being written in the ninth century and drawing heavily upon these same Abbasid roots.

For that reason, I would view a tradition claiming Yazdegerd considered converting to Islam with as much suspicion as the tradition that Muhammad himself offered Heraclius the opportunity to do so. In any case, I think it's unlikely that "Islam" as a real religious concept existed as early as the 630s- what you had were monotheistic Arabs who followed the teachings of a religious leader called Muhammad, but saying more than this is straying into dangerous territory- I would argue that Islam probably only began to properly crystallise under Abd-al-Malik, and the process was not really complete until after 750. The examples I like to bring up to support this are the total absence of inscriptions referring to Islam at any point in the seventh century, and the figurative drawings and mosaics, plus inscribed crosses, on early Ummayyad-era public buildings.

With all that said:

I don't think it'll be possible for Yazdegerd to come to an accommodation with the Arabs that leaves him with his crown- for the sake of the conquest of Iranshahr, the House of Sasan has to go. Remember that the Arabs of the seventh century seem to have been rather a racist lot, who kept themselves firmly segregated from conquered populations, and strongly discouraged any sort of integration; later this would spell the downfall of the Ummayyads when Islamised Persians destroyed their rule in the 740s.

Best case scenario for Yazdegerd is he keeps his life, and is able to somehow flee into Roman territory, but I think even this is pretty unlikely. As I say, the House of Sasan cannot really be allowed to survive from the POV of the seventh century Arabs.
 
Historian Touraj Daryaee, based on archaeological evidence, has recently concluded that theSassanid empire was in the middle of a civil war when the Arabs attacked. He evidences this by the staggering amount of kings in such a short period of time and by the fact that the various kings had coins minted in various parts of the empire. That bing the case, I dont think Yazdegerd converting would have much effect as wouldnt have been in control of such a large territory.
 
Quite true, his control had slipped especially in the eastern regions of the Empire. As the regional leaders there failed to send troops to aid him. When the Persians were defeated and Yazdegerd fled eastward his reception was outright hostile.
 
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