Iranian peoples
Starting with the reign of Omar in 634 AD, Muslim Arabs began a conquest of the Iranian Plateau. The Arabs conquered the Sassanid Empire of the Persians and seized much of the Byzantine Empire populated by the Kurds and others. Ultimately, the various Iranian peoples, including the Persians, Pashtuns, Kurds and Balochis, converted to Islam, while the Alans converted to Christianity, thus laying the foundation for the fact that the modern-day Ossetians are Christian. The Iranian peoples would later split along sectarian lines as the Persians adopted the Shi'a sect. As ancient tribes and identities changed, so did the Iranian peoples, many of whom assimilated foreign cultures and peoples.