How did Islam spread?

Initially, the Arabs did not close Christian and other churches, did not prevent residents from performing religious rituals in them, but all non-Muslims were imposed unaffordable taxes, from which only those who converted to Islam were exempted. Therefore, after several centuries, the once Christian countries – such as Egypt, Syria, Palestine – became Islamic, and their inhabitants began to speak Arabic. The population of Iran, Central Asia, North-West India was converted to Islam, but local languages ​​have survived here. Islam spread to other lands outside the caliphate.
Islam split into two streams. Ali’s supporters began to be called Shiites, and supporters of the Umayyads and other caliphs – Sunnis, since, in addition to the Koran, they considered the Sunna to be the holy book.

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