Nizari–Seljuk conflicts
By the late 11th century, the Shi'a sub-sect of Ismailism (later Nizari Ismailism) had found many adherents in Persia, although the region was occupied by the Sunni Seljuk Empire. The hostile tendencies of the Abbasid–Seljuk order triggered a revolt by Ismailis in Persia under Hassan-i Sabbah, starting the so-called Alamut Period.