Al-Amir bi-Ahkam Allah

Abu Ali al-Mansur ibn al-Musta'li, better known by his regnal name al-Amir bi-Ahkam Allah was the tenth Fatimid Caliph, and the 20th Imam of Musta'li Isma'ili sect of Shia Islam, from 1101 to his death in 1130. Until 1121, he was a de facto puppet ruler of his uncle and father-in-law, the vizier al-Afdal Shahanshah. When the latter was murdered, possibly with al-Amir's connivance, the caliph appointed al-Ma'mun al-Bata'ihi as vizier, but took an increasing role in government, and after 1125 ruled without a vizier. His reign saw the progressive loss of all Fatimid strongholds in Palestine to the Crusaders apart from Ascalon. His assassination in 1130, leaving only his infant son al-Tayyib as heir, threw the Fatimid regime into a succession struggle during which it almost collapsed. Fatimid rule was restored with the succession of al-Amir's cousin al-Hafiz li-Din Allah in 1132, which led to the division of Musta'li Isma'ilism into the rival Hafizi and Tayyibi branches.