Slavic populations were Christianized between the 7th and 12th centuries. Orthodox Christianity is predominant among East and South Slavs, while Catholicism is predominant among West Slavs and some western South Slavs. The religious borders are largely comparable to the East–West Schism which began in the 11th century. Islam first arrived in the 7th century during the early Muslim conquests, and was gradually adopted by a number of Slavic ethnic groups through the centuries in the Balkans. Among Slavic populations who profess a religion, the majority of contemporary Christian Slavs are Orthodox, followed by Catholic. The majority of Muslim Slavs follow the Hanafi school of the Sunni branch of Islam. Religious delineations by nationality can be very sharp; usually in the Slavic ethnic groups, the vast majority of religious people share the same religion. Mainly Eastern Orthodoxy: Russians Ukrainians Serbs Bulgarians Belarusians Macedonians Montenegrins Mainly Catholicism: Poles (incl. Silesians, Kashubians, Gorals) Croats Slovaks Slovenes Sorbs Rusyns Banat Bulgarians Mainly Islam: Bosniaks Pomaks Gorani Torbeši Ethnic Muslims Relations with non-Slavic people Throughout their history, Slavs came into contact with non-Slavic groups. In the postulated homeland region (present-day Ukraine), they had contacts with the Iranian Sarmatians and the Germanic Goths. After their subsequent spread, the Slavs began assimilating non-Slavic peoples. For example, in the Balkans, there were Paleo-Balkan peoples, such as Romanized and Hellenized (Jireček Line) Illyrians, Thracians and Dacians, as well as Greeks and Celtic Scordisci and Serdi. Because Slavs were so numerous, most indigenous populations of the Balkans were Slavicized. Thracians and Illyrians mixed as ethnic groups in this period. A notable exception is Greece, where Slavs were Hellenized because Greeks were more numerous, especially with more Greeks returning to Greece in the 9th century and the influence of the church and administration, however, Slavicized regions within Macedonia, Thrace and Moesia Inferior also had a larger portion of locals compared to migrating Slavs. Other notable exceptions are the territory of present-day Romania and Hungary, where Slavs settled en route to present-day Greece, North Macedonia, Bulgaria and East Thrace but assimilated, and the modern Albanian nation which claims descent from Illyrians and other Balkan tribes. The status of the Bulgars as a ruling class and their control of the land nominally left their legacy in the Bulgarian country and people, but Bulgars were gradually also Slavicized into the present-day South Slavic ethnic group known as Bulgarians. The Romance speakers within the fortified