Limes Arabicus

It ran northeast from the Gulf of Aqaba for about 1,500 kilometers (930 mi) at its greatest extent, reaching northern Syria and forming part of the wider Roman limes system.

Next to the Limes Arabicus Emperor Trajan built a major road, the Via Nova Traiana, from Bosra to Aila on the Red Sea, a distance of 430 km (270 mi).

Built between 111 and 114 AD, its primary purpose may have been to provide efficient transportation for troop movements and government officials as well as facilitating and protecting trade caravans emerging from the Arabian Peninsula.

One important fort was Qasr Azraq, another was at Humeima (Latin: Auara), from the late 2nd century AD, on the Via Traiana Nova from Petra to Aila, where up to 500 auxiliary troops could have resided.

Diocletian engaged in a major military expansion in the region, building a number of castella, watchtowers, and fortresses along the fringe of the desert just east of the Via Nova.

[6] There were castra every 100 kilometres (62 mi) with the purpose to create a line of protection and control:[7] in the south there was the legionary fortress at Adrou (Udruh), just east of Petra.