Limes Arabicus in the context of "Watchtower"

Lucius Septimius Severus (/səˈvɪərəs/; Latin: [ˈɫuːkiʊs sɛpˈtɪmiʊs sɛˈweːrʊs]; 11 April 145 – 4 February 211) was Roman emperor from 193 to 211. He was born in Leptis Magna, Libya in the Roman province of Africa. As a young man he advanced through the customary succession of offices under the reigns of Marcus Aurelius and Commodus. Severus was the final contender to seize power after the death of the emperor Pertinax in 193 during the Year of the Five Emperors.

After deposing and killing the incumbent emperor Didius Julianus, Severus fought his rival claimants, the Roman generals Pescennius Niger and Clodius Albinus. Niger was defeated in 194 at the Battle of Issus in Cilicia. Later that year Severus waged a short punitive campaign beyond the eastern frontier, annexing the Kingdom of Osroene as a new province. Severus defeated Albinus three years later at the Battle of Lugdunum in Gaul. Following the consolidation of his rule over the western provinces, Severus waged another brief, more successful war in the east against the Parthian Empire, sacking their capital Ctesiphon in 197 and expanding the eastern frontier to the Tigris. He then enlarged and fortified the Limes Arabicus in Arabia Petraea. In 202, he campaigned in Africa and Mauretania against the Garamantes, capturing their capital Garama, and expanding the Limes Tripolitanus along the southern desert frontier of the empire.

Arabia Petraea (lit. 'Rocky Arabia') was a Roman province from the 2nd century to the 7th century. It was established after the Roman Empire conquered the Nabataean Kingdom in 106 and existed until the Muslim conquest of the Levant in the 630s. Spanning much of the Sinai Peninsula and part of the Levant, it was bordered by Syria to the north, by Judaea (later Syria Palaestina) to the west, and by Egypt to the southwest. To the east and southeast of Arabia Petraea was non-Roman territory that the Romans knew as Arabia Deserta. These two regions, together with a third region in South Arabia that was called Arabia Felix, accounted for the Arabian Peninsula in Roman geography.

Annexed by Trajan (r. 98–117), Arabia Petraea was a key province along the Limes Arabicus, which delineated the Roman Empire's borders throughout the Arabian Desert. It was also the only province in the Near East that the Romans did not gain and subsequently lose during Trajan's reign, unlike Armenia, Assyria, and Mesopotamia. The province's capital city was initially Petra, as it had been under the Nabataeans, but Bosra later served in this capacity. Most of the province's land was a vast desert that was sparsely populated by nomadic Arab tribes, though there were several urban settlements closer to the Jordan River.

The Banu Kalb (Arabic: بنو كلب, romanized: Banū Kalb) was an Arab tribe which mainly dwelt in the desert and steppe of northwestern Arabia and central Syria.

It was involved in the tribal politics of the Byzantine Empire's eastern frontiers, possibly as early as the 4th century. By the 6th century, the Kalb had largely adopted Christianity and came under the authority of the Ghassanids, leaders of the Byzantines' Arab allies. During the lifetime of the Islamic prophet Muhammad, a few of his close companions were Kalbites, most prominently Zayd ibn Haritha and Dihya, but the bulk of the tribe remained Christian at the time of Muhammad's death in 632. They began converting in large numbers when the Muslims made significant progress in the conquest of Byzantine Syria, in which the Kalb stayed neutral. As a massive nomadic tribe with considerable military experience, the Kalb was sought as a key ally by the Muslim state. The leading clans of the Kalb forged marital ties with the Umayyad family, and the tribe became the military foundation of the Syria-based Umayyad Caliphate (661–750) from the reign of Mu'awiya I (r. 661–680) to the early reign of Abd al-Malik (r. 685–705).

The Salīḥids (Arabic: بنو سليح, romanized: Banū Salīḥ), also known simply as Salīḥ or by their royal house, the Zokomids (Arabic: Ḍajaʿima) were the dominant Arab foederati of the Byzantine Empire in the 5th century. They succeeded the Tanukhids, who were dominant in the 4th century, and were in turn defeated and replaced by the Ghassanids in the early 6th century.

The Salihids were originally concentrated in the Wadi Sirhan and Balqa regions of modern Jordan, but spread as far as northern Syria after entering the service of the Byzantine Empire. The Salihids were charged with collecting tax from Bedouins dwelling within the Limes Arabicus (Byzantine frontier with the Syrian and Arabian deserts) and protecting the frontier from Bedouin raiders. They were ardent Christians and at least one of their phylarchs and kings, Dawud, built a Christian monastery, Deir Dawud.