Ali ibn al-Athir
The Assassins were a Nizari Isma'ili sect of Shia Islam who lived in the mountains of Persia and in Syria between 1090 and 1275. During that time, they held a strict subterfuge policy throughout the Middle East through the covert murder of first Muslim and later Christian leaders who were considered enemies of their state. The modern term assassination is based on the tactics used by the Assassins. Nizari Isma'ilism formed in the late 11th century after a succession crisis within the Fatimid Caliphate between Nizar ibn al-Mustansir and his half-brother, caliph al-Musta'li. Contemporaneous historians include Arabs ibn al-Qalanisi and Ali ibn al-Athir and the Persian Ata-Malik Juvayni. The first two referred to the Assassins as "batiniyya", an epithet widely accepted by Isma'ilis themselves.