In 610, Muhammad, an Arab from Mecca, claimed that God was speaking to him. The people of Mecca, mostly from the Quraysh tribe, worshipped many gods. Muhammad said that there was only one God. Muhammad founded the religion of Islam, and his followers, called Muslims, conquered Arabia by war. After Muhammad died in 632, men called caliphs ruled the Muslims in empires called caliphates. These include the Rashidun, Umayyad, and Abbasid caliphates. Some parts of Arabia, including Oman, were not always part of the caliphates. Rulers from the 900s to the 1200s included the Fatimid Caliphate, Seljuk Empire, and Ayyubid dynasty. Islam was divided into two forms called Sunni and Shi'a, who fought wars against each other. Yemen and Oman were ruled by different people at times, including the Rasulid dynasty in Yemen.