The large area which in the second and third centuries made up the Roman province of ' Arabia' was composed of several different zones with different histories. What united them was above all the presence of a steppe, which in the south became a barren mountain zone (the northern part of the Hedjaz, stretching down the east coast of the Red Sea). The southern part of the area had indeed two distinctive characteristics. First, like the whole of the eventual Roman 'frontier', from the Red Sea to Mesopotamia, it bordered on a steppe whose inhabitants were not under Rome's military or political control; but here there was also the important factor of an inner 'frontier', with a similarly unsettled population, the desert and mountains of Sinai. Second, the existence of Nabataean and then Roman ports on the Red Sea meant that there were important cultural and trading contacts with Egypt, with Arabia Felix (the Yemen) and with the Indian Ocean.
It is tempting to try to write a history of the rise and fall of the Red Sea trade passing through the kingdom of Nabataea and the subsequent province of Arabia, as if the accidents of narrative references could allow any such thing. All that needs to be stressed now is that this trade never disappeared altogether. Eusebius, in his priceless series of snapshots of Palestine and Arabia as they were in about AD 300, refers to Aila (Aqaba/Elath) as 'on the borders (of Palestine, as it now was), lying next to the southern desert and to the Red Sea which is beside it, sailed by those voyaging from Egypt and those from India. The tenth Roman legion is stationed there'.1____________________