If they were able to sack Meroë iotl why weren’t they able to conquer and hold it? Did Aksum have the ability to actually hold Nubia? Nubia was not just different culturally but religiously as well, so incorporating that won’t be easy. Then we still run into the issue of Egypt and the Romans. You need them to be far far weaker than iotl to hope or conquering Egypt, seeing as how it’s arguably the most important province in the empire. You would need the empire to at least be as bad as it was upon the onset of the Arab conquest. As well as have the Sassanids be internally focused or focused on the East so it doesn’t take advantage of a crumbling Rome.
That’s why I find this idea far fetched to say the least. It required that not only is Aksum wanked but the two main empires of the region somehow be as bad as they were upon the onset of the Arab conquests. You need PODs for these things to happen. What’s a POD that could cause Aksum to be more imperialistic? Where it could take Nubia and successfully incorporate it? What’s a POD that would cause the Roman Empire to be so poorly off that it couldn’t defend its most valued province? What’s a POD that would cause the Sassanid Empire to be poorly led/unstable/focused elsewhere? So much needs to change for this to happen that I just find it plausible. The Songhai idea by
@CastIron is still the one I find to be most plausible even if I still have my doubts.
This is a pretty interesting discussion.
I
do think that the Kingdom of Aksum is the best candidate to satisfy the AHC, but I'd like to propose an alternative PoD.
There are a lot of problems getting a sub-Saharan state all the way to Europe, but it's mostly a question of distance. To get to Europe from anywhere in sub-Saharan Africa, you've got to go by land or by sea. Back then, that means by horse, camel, or by boat. Historically, sub-Saharan Africa lagged in terms of naval technology. A smooth coastline and unfavorable currents undoubtedly have a lot to do with it. Historically, sub-Saharan Africa is
also not the best place to raise horses, so the cavalry tradition in those states was usually not quite as robust as it was in other places (and to boot, camels are not native to Africa). Those are two big issues, and only in the Kingdom of Aksum does it seem that you might be able to surmount them.
That's because OTL, the Kingdom of Aksum actually
did conquer Yemen at one point, set up a vassal state with an Aksumite viceroy in charge, and managed to hold onto it for about fifty years, when IIRC, the Sassanids allied with a rebellious Aksumite and chased the ruling Aksumites out. So my PoD for this would be that the Aksumites manage to hold onto Yemen. Preferably, they do this without having to fight off the Sassanids at all.
If they control both sides of the mouth of the Red Sea, that gives them the ability to raise revenue
and gives them motive, means, and opportunity to focus on the development of naval technology. Furthermore, territory on the Arabian peninsula will give them access to camels and some of the best horses in the world, which might allow them to develop a more robust cavalry tradition.
Also, that means that when Muhammed comes around, there's a powerful Christian Kingdom on the Arabian peninsula. ITTL, does Muhammed send some of his followers to the Kingdom to escape persecution, as he did OTL? For the sake of this AHC, let's say he doesn't. So things don't get too wonky, let's say that Muhammed still takes the Hijra to Medina on schedule, but his numbers aren't bolstered by the inclusion of the Aksumite colonists. If Muhammed still manages to subdue the tribes around Medina, he's still sandwiched between the Sassanids and the Aksumites, neither of whom has tired themselves out by fighting amongst themselves.
Now, even if the Sassanids don't overextend themselves fighting in southern Arabia, by the early 600s, they're still locked in a death embrace with the Byzantines. So Muhammed looks to the north and south from his position in Mecca, decides against going south (where the Aksumites are strong), and instead swings east toward Oman, and then north to Mesopotamia. This brings him and the righteous Caliphs in conflict with the Sassanids earlier. The Sassanids, though still weakened, are slightly stronger than OTL, and manage to blunt some of the Caliphate's furious momentum.
Things will get wackier from here.
If the Caliphate can be confined to the northern half of Arabia and Mesopotamia, they'll turn toward the Holy Land soon enough. Then maybe you can get the Patriarchs of Alexandria and Constantinople to call for some kind of proto-crusade to quash them. (Maybe.) Anyway, the Caliphate is in a very unenviable strategic position, with enemies on three sides. If you posit a Byzantine-Aksumite victory, then the Aksumites could end up with dominion over the whole of the Arabian peninsula. At that point, Aksum would such a big, powerful empire that it's conceivable to imagine them briefly projecting power as far north as Cyprus, though it's hard to see them holding it for any length of time.
That's about all I got.