Ghassanid phylarch) al-Mundhir III was arrested and exiled. This led to a rebellion in the Hauran and a siege on Bosra led by al-Mundhir's son al-Nu'man VI, which only ended when the latter was allowed by the Byzantines to reestablish the Ghassanid phylarchy. This only lasted until al-Nu'man was exiled in 584, after which the empire dissolved the phylarchy into numerous, smaller Ghassanid and other Arab Christian units. Some of these units continued to fight alongside the Byzantines, but their overall power had diminished, leaving the area more vulnerable to invasion. In 613, the Sassanian Persians invaded Syria and defeated the Byzantines in a battle between Adraa and Bosra. The Byzantine era in the Hauran was marked by the dual processes of rapid Arabization and the growth of Christianity. The region's Ghassanid rulers were semi-nomadic and established permanent encampments throughout the Hauran, chief of which was al-Jabiya, but also Aqraba, Jalliq, Harith al-Jawlan and others. They were entrusted by the Byzantines to secure the Hauran's agricultural production and stave off nomadic marauders. The region prospered under Ghassanid supervision and the tribe itself built or patronized secular and religious architecture in the region's villages, including churches, monasteries and large homes for their chieftains. Although a Christian presence in some cities of Auranitis was established in the 2nd and 3rd centuries, by the 5th century nearly all the villages in the Hauran had churches, most of them dedicated to saints favored by the Arabs. The Ghassanids played a significant role in promoting Monophysite Christianity in Syria which was viewed as heretic by the Chalcedonian Church embraced by most Byzantine emperors. Early Islamic era The advent of Islam in Arabia and its expansion northward to Syria was countered by the Byzantines and their Arab Christian allies. However, the region's defenses had been significantly weakened as a consequence of the Ghassanids' decline in status in 582–584. The first Arab Muslim forces arrived in the Hauran in April 634 and Bosra was conquered by them in May. Following the decisive Muslim victory in the Battle of Yarmouk in 636, all of the Hauran came under Muslim rule. The Umayyad dynasty took control of the expanding Islamic caliphate and relocated its capital from Medina to Damascus and were supported by the people of Hauran. After the death of the Umayyad caliph Mu'awiya II and the ensuing chaos of succession, the Umayyads' Arab tribal allies in Syria