The second chapter narrates the history of North Arabia between the late third and fifth centuries. In around 224, the Arsacid dynasty in Iran was defeated by the Sasanians, who immediately embarked on a war against Rome. The renewed animosity between the two superpowers of Late Antiquity had repercussions in the Near East, causing the fall of valuable buffer states such as Palmyra and Hatra and the employment of Arabian allies in areas such as North Ḥijāz, where the Romans could no longer easily exercise direct control. These Arabian allied confederacies did not have fixed geographical boundaries and were also often unstable in their alliances. After shedding light on the sociopolitical situation of North Arabia, the chapter focuses on the impact of Constantine’s conversion to Christianity, which had the result of creating a cultural network. It argues that Christianity had an instrumental role for the North Arabian urban elites and a more limited role among the poorer classes, especially the rural ones.