( ; ; ; ; ) is a branch of Shia Islam. The () get their name from their acceptance of Isma'il ibn Jafar as the appointed spiritual successor () to Ja'far al-Sadiq, wherein they differ from the Twelvers, who accept Musa al-Kadhim, younger brother of Isma'il, as the . Tracing its earliest theology to the lifetime of Muhammad, Ismailism rose at one point to become the largest branch of Shī‘ism, climaxing as a political power with the Fatimid Caliphate in the tenth through twelfth centuries. Ismailis believe in the oneness of God, as well as the closing of divine revelation with Muhammad, whom they see as "the final Prophet and Messenger of God to all humanity". The Ismāʿīlī and the Twelvers both accept the same initial Imams from the descendants of Muhammad through his daughter Fatimah and therefore share much of their early history. Both groups see the family of Muhammad (the Ahl al-Bayt) as divinely chosen, infallible (ismah), and guided by God to lead the Islamic community (Ummah), a belief that distinguishes them from the majority Sunni branch of Islam.