During the Early Roman period (63 B.C.–A.D. 135), Transjordan was an integral part of the Nabataean Kingdom. To safeguard their borders, settlements, and vital caravan routes, the Nabataeans devised a network of small forts and watchtowers. These structures were often newly built or constructed atop the remains of Iron Age fortifications.

When the Romans annexed the Nabataean state in A.D. 106, these defensive positions were seamlessly integrated into the emerging limes system—Rome’s intricate frontier defence network. The Nabataean fortifications effectively formed the foundational framework of what became known as the Limes Arabicus. While identifying this transition is more challenging in the northern areas of Transjordan due to the lack of Nabataean pottery, evidence from sites like Deir El-Kahf and Qasr Al-Hallabat, which feature Early Roman pottery, hints at earlier Nabataean military occupation.

Not content with just utilising existing structures, the Romans began expanding and establishing new ones as well. For instance, they constructed Qasr El-Kithara in the southernmost regions during the annexation. Significant effort was also directed at developing a key north-south road, the Via Nova Traiana, which connected the provincial capital of Bostra to Aqaba (Aila). By A.D. 111, this vital road was complete, enhancing mobility and connectivity across the province.

The Late Roman period (A.D. 135–284) witnessed a marked increase in the number of fortifications. Many Nabataean forts were either expanded or reconstructed, and prominent new installations like Dajanya, Al-Hallabat, and Qasr Usaykhim sprang up. Rather than focusing on a particular area, the Romans ensured the entire frontier received attention, reflecting the importance of maintaining stability across this volatile region. While much of the second century was defined by peace under Roman rule, the third century brought instability in the form of civil wars, invasions, and the meteoric rise of Palmyra. Palmyrene dominance, which extended as far as Egypt, severely disrupted Roman efforts in Arabia and beyond.

With the fall of Palmyra under Emperor Aurelian (A.D. 270–275), the Romans embarked on a period of reconstruction. Emperor Diocletian (A.D. 284–324) led these efforts with a particular focus on fortifying the empire’s northwestern regions. During this time, strategic forts like Qasr Azraq, Qasr Uweinid, and Qasr Usaykhim formed a defensive line to control movement from the Sirhan area. Meanwhile, the construction of key forts like Zona, Qasr Thuraia, Qasr Bshir, and Khirbet el Fityan strengthened the central sector of the Limes Arabicus. Of particular importance were the two massive camps at El-Lejjun and Udhruh, near the iconic city of Petra. These installations underscored the Romans’ commitment to securing the region during this tumultuous period.

By the 4th century, the Roman frontier remained robust, but it began to decline during the Early Byzantine period (A.D. 392–450). By the end of the 5th century, most forts in Arabia were abandoned, marking a gradual cessation of direct Roman military presence. This withdrawal may, in part, be attributed to the Byzantine Empire’s reliance on the Ghassanids, local vassals trusted to manage and defend the region in their stead.

Together, these fortifications tell a story of resilience, adaptation, and the enduring strategic importance of Transjordan. From the Nabataean Kingdom to the Roman Empire and beyond, the region stood as a vital juncture between civilisations, guarded by an evolving network of forts and frontier lines that shaped its history.