The Ghassanids (, also Banu Ghassān (, romanized as: ), also called the Jafnids, were an Arab tribe which founded a kingdom. They emigrated from southern Arabia in the early 3rd century to the Levant region. Some merged with Hellenized Christian communities, converting to Christianity in the first few centuries AD, while others may have already been Christians before emigrating north to escape religious persecution. After settling in the Levant, the Ghassanids became a client state to the Byzantine Empire and fought alongside them against the Persian Sassanids and their Arab vassals, the Lakhmids. The lands of the Ghassanids also acted as a buffer zone protecting lands that had been annexed by the Romans against raids by Bedouin tribes. Few Ghassanids became Muslim following the Muslim conquest of the Levant; most Ghassanids remained Christian and joined Melkite and Syriac communities within what is now Jordan, Israel, Palestine, Syria and Lebanon. Traditional genealogy and migration from South Arabia In the Arab genealogical tradition which developed during the early Islamic period, the Ghassanids were considered a branch of the Azd tribe of South Arabia/Yemen. In this genealogical scheme, their ancestor was Jafna, a son of Amr Muzayqiya ibn Mazin ibn Azd, through whom the Ghassanids were purportedly linked with the Ansar (the Aws and Khazraj tribes of Medina), who were the descendants of Jafna's brother Tha'laba. According to the historian Brian Ulrich, the links between Ghassan, the Ansar, and the wider Azd are historically tenuous, as these groups are almost always counted separately from each other in sources other than post-8th-century genealogical works and the story of the 'Scattering of Azd'. In the latter story, the Azd migrate northward from Yemen and different groups of the tribe split off in different directions, with the Ghassan being one such group. Per the 'Scattering of Azd' story, the Ghassanids eventually settled within the Roman limes. The tradition of Ghassanid migration finds support in the Geography of Claudius Ptolemy, which locates a tribe called the Kassanitai south of the Kinaidokolpitai and the river Baitios (probably the wādī Baysh). These are probably the people called Casani in Pliny the Elder, Gasandoi in Diodorus Siculus and Kasandreis in Photios (relying on older sources). The date of the migration to the Levant is unclear, but they are believed to have arrived in the region of Syria between 250 and 300 AD and later waves of migration circa 400