After Muhammad's death came the ruling of Abu Bakr and the development of the Islamic civilization. Abu Bakr's rule was followed by three other caliphs, the last being Ali. Ali's death ended the leadership of the Four Rightly Guided Caliphs, and marked the beginning of the Umayyad Dynasty. At the Battle of Tours, the Umayyad Dynasty came to an end. This was also a time when the religion of Islam split into the sects of Sunni and Shi'a. The Muslims conquered the cities of Jerusalem and Damascus, and eventually moved the Islamic capital to Baghdad. In 1258, Baghdad fell to the Mongols, ending the Golden Age of the Islamic civilization. However, Islam lives on today as one of the major world religions.