According to historian Irfan Shahid, evidence suggests clans of the Tayy moved into Byzantine-held Syria beginning in the 6th century. By then, the Ghassanids had largely supplanted the Salihids as the Byzantines' main foederati, and the Salihids began living alongside the Tayy in the region of Kufa. In the late 6th century, the Al al-Ghawth and Al Jadila fought against each other in the 25-year-long Fasad War (harb al-Fasad) in northern Arabia. Numerous atrocities were committed by both factions and the war resulted in the migration of several Jadila clans from the north Arabian plains to Syria, while the Al Al-Ghawth remained in Jabal Aja and Jabal Salma. The Jadila tribesmen founded a hadir (military encampment) near Qinnasrin (Chalcis) called Hadir Tayyi after the tribe. The Ghassanid king al-Harith ibn Jabalah brokered a peace between the Tayy factions, ending the Fasad War. Afterward, the Tayy's relations with the Ghassanids, which had previously been checkered, were much improved. The Al Jadila converted to Christianity, the religion adopted decades earlier by the Ghassanids. Some other clans of the Banu Tayy remained pagan, worshiping the deities of Ruda and al-Fils. Those who converted to Christianity apparently embraced their new faith zealously and produced two well-known priests, named in Syriac sources as Abraham and Daniel.