The Arab conquest of the Levant in 635 CE under ʿUmar ibn al-Khaṭṭāb led to significant demographic changes. The region, renamed Bilad al-Sham, saw a decline in population from an estimated 1 million in Roman and Byzantine times to about 300,000 by the early Ottoman period. This demographic shift was due to a combination of factors, including the flight of non-Muslim populations, immigration of Muslims, local conversions, and a gradual process of Islamization.^[138]

Following the conquest, Arab tribes settled in the area, contributing to the spread of Islam. The Muslim population grew steadily, becoming dominant both politically and socially.^[139] Many Christians and Samaritans from the Byzantine upper class migrated to northern Syria, Cyprus, and other regions, leading to the depopulation of coastal towns. These towns, like Ashkelon, Acre, Arsuf, and Gaza, were resettled by Muslims and developed into significant Muslim centers.^[140] The region of Samaria also experienced Islamization due to conversions and Muslim influx.^[138] Two military districts—Jund Filastin and Jund al-Urdunn—were established in Palestine. The Byzantine ban on Jews living in Jerusalem came to an end.

The demographic situation further evolved under Abbasid rule, particularly after the 749 earthquake. This period saw increased emigration of Jews, Christians, and Samaritans to diaspora communities, while those who remained often converted to Islam. The Samaritan population in particular faced severe challenges such as droughts, earthquakes, religious persecution, and heavy taxes, leading to a significant decline and conversions to Islam.^[139]

Throughout these changes, forced conversions were not prevalent, and the impact of the jizya tax on religious conversions is not clearly evidenced. By the Crusader period, the Muslim population, although growing, was still a minority in a predominantly Christian region.^[139]