My Classics professor sent me a link to a Zoom conference on archaeology and the speaker (A. Asa Eger) was talking about the physical border between the Byzantine Empire and the Islamic Empire. He talked about literary sources on the retreat of the Byzantines from Syria (and why it was important in the Islamic world) and then the geographical features separating Byzantine-held Anatolia from Arab-held Syria. I couldn’t find a recording of the webinar, but I found the speaker published a book that seems to have a lot of the same material: