The lands in the middle east changed hands so many times that you had a generation be born and grow into adulthood without having being firmly associated with one empire or the other.
You had the nomadic tribes grow rich from their mercenary work for either empire.
You also had the fact that both Christian and Zoroastrian faiths took huge blows as the true cross was stolen by the Persians and then the Roman army destroyed the most important Zoroastrian fire temple and snuffed out the eternal flame there.
And finally after the Persians were defeated by the Caliphate, you the the Romans, against their well established strategies, gather their forces for a decisive battle, and then make tactical mistakes allowing for defeat.
It was the perfect storm of the right place, at the right time, with rolling nat 20s.
Its not even clear how 'Islamic' the early armies were, they might have considerable Christian and Jewish portions. How differentiated early Islam was from certain version if Christianity is up for debated.
I also think just going with the 'right place, right time' narrative misses good coalition billing, good generalship and other things they did very well. Both Rome and Persia had thought a great number of wars in its history, and faced many 'barbarian' invasion, sometimes from forces that on paper were more impressive, that invaded during ongoing peer conflicts and despite that had been successful.
The early Islamic preachers in what became Indonesia and Malaysia were South Asian or Iranian in origin, and a major reason why Persianate motifs are prominent in Southeast Asian Islam. Same with much of Central Asia.
That would have not happened if the Byzantine-Sassanid War did not happen, because what became Yemen and Oman would have remained under Sassanid suzerainity and much of the Levant would have remained Byzantine. And thus, Khorasan, Gujarat, Sindh, and Punjab would have not become Muslim.
That said, I agree with you that the spread of Islam was HEAVILY dependent on trade.
There is a one thousand year old mosque in Beijing. There are ethnic Hans who converted (now the Hui minority). There was a sizeable Muslim community in Guangdong in the Tang Dynasty.
The same holds true, as far as I know, throughout South East Asia.
My point is simply that Islam could and did spread peacefully, like Christianity did before it. So it is difficult to draw drastic conclusions, IMHO.
The spread of Islam to China was only made possible through the spread of Islam first to Sogdiana, and that happened through quite violent means as we know from the written record.
Even in the 16th century if you read the Baburnama, pagans and non-Muslims were common across Central Asia and even Muslims like Babur were lax in their religiosity (drinking wine, eating pork, etc).
In most cases, religion didn't largely solidify until the 19th-20th century with the rise of the nation state and nationalism.
Religious nationalism in the modern sense (eg. Political Islam, Political Christianity, Hindutva, etc) only really began in the late 19th century when Rationalist (in the actual philosophical sense - not the tech bro bullcrap) and Enlightenment era thought began spreading.
> they were gone by approximately the year 1000 CE
Absolutely not.
Nestorian Christianity and Buddhism remained common in inner Asia until the 13th century with the Mongol invasions.
Depending on where you draw the line for Central Asia, non-Muslim religions remained significantly practiced in Central Asia well beyond that era as well.
At one point, the Tibetan empire even controlled Kabul during that era, and the Turk Shahis remained Buddhist or Hindu (depending on the leader) well beyond that era.
Even the leader of the Ghurid dynasty (Muhammad ibn Suri) was a Buddhist or Hindu Turk despite using a Muslim name.
I was talking about Sogdiana, not other regions of Central Asia, and 1000 CE is a standard cutoff date in scholarship for the end of the other world religions there.
Like, I always thought that the Umayyad elites sometimes didn't even want people to convert, lest their privilege become diluted.
Even if we would accept that their bows were better then some other steppe peoples, he still thought many people that for sure had the same bows as he did.
In fact, most of his life, he thought people who had the same technology, including the invasion of the Qara Khitai.
Then the Jin had allies that likely had the same bow technology. However it seems most of those allies just switched sides.
Only the Khwarazmian Empire and Xia likely didn't have significant troops armed the same way.
His great accomplishment was marrying that with the ability to besiege walled cities. Nobody expected barbarian horse archers to be able to do that.
https://www.nationalgeographic.com/science/article/140310-ge...
In terms of numbers, it's entirely possible that larger numbers of defending sedentary soldiers are needed than attacking horse-riding nomad soldiers for the former to mount an effective defense against the latter.