Islam came to Yemen around 630 during Muhammad's lifetime and the rule of the Persian governor Badhan. Thereafter, Yemen was ruled as part of Arab-Islamic caliphates, and became a province in the Islamic empire.
Regimes affiliated to the Egyptian Fatimid caliphs occupied much of northern and southern Yemen throughout the 11th century, including the Sulayhids and Zurayids, but the country was rarely unified for any long period of time. Local control in the Middle Ages was exerted by a succession of families which included the Ziyadids (818–1018), the Najahids (1022–1158), the Egyptian Ayyubids (1174–1229) and the Turkoman Rasulids (1229–1454). The most long-lived, and for the future most important polity, was founded in 897 by Yayha bin Husayn bin Qasim ar-Rassi. They were the Zaydis of Sa'dah in the highlands of North Yemen, headed by imams of various Sayyid lineages. As ruling Imams of Yemen, they established a Shia theocratic political structure that survived with some intervals until 1962.
