@Falecius
Why is Suez not a good stopping point?
In one word, desert.
I get that it is desert terrain ideal for Bedouin, but the Suez isthmus is relatively narrow. Certainly narrower and less vulnerable to flanking over the long term compared to portions of Africa west of Egypt.
Yes, but in the early phase of the conquest, the Arabs do not appear to have ventured deep into the Sahara. They did not need to, by the way, in order to "flank" Roman coastal positions.
You made a remark about Suez being difficult to fortify – Is that because supplying Byzantine garrisons with water would be too daunting?
I would say so. Historical precedents suggest that, after people have camels, the Suez isthmus is more a causeway than a border.
What about defenses closer in to the Nile delta. I figure the Nile Delta and Nile Vally could support large garrisons in terms of waterThIn the Nile,, the garrisons and forts should not go thirsty. This does lket the Bedouin range the eastern deseert in Eguypt however. Perhaps that dooms the defense Egypt as the Byzzies cannot be strong everywhere, the Arabs could ford the Nile at some point, and operate well in both desert flanks of the Nile Valley?
I suppose so.
I get how North Africa to the west is further outside of Arab range, and it was defended longer.
There I think there is good hope of possibly holding on to Tunisia for a prolonged period, but I think that is unlikely to halt Islamic expansion to the west via the Saraha in the long or even medium term.
The Arabs are likely to expand via the Sahara and eventually meet up with and convert desert berbers, and assault coastal points from there..
It depends on how solid Byzantine rule in Africa is. IOTL, the Arabs came when it was shaky; the Berbers controlled most of the area already, and they were the largest force opposing the Arabs in the early first, before converting (relatively early too, but also quite superfically at first, as noted).