This chapter will cover the initial phase in the history of Nizārī Ismāʿīlism, coinciding with the so-called Alamūt period from around 483/1090 to 654/1256. Ḥasan-i Ṣabbāḥ was operating in Persia as an Ismāʿīlī dāʿī and his seizure of the fortress of Alamūt in 483/1090 marked the effective foundation of what was to become the Nizārī Ismāʿīlī state of Persia and Syria. As the undisputed leader of the Persian Ismāʿīlīs, Ḥasan was already following an independent revolutionary policy against the Saljūq Turks when the Fāṭimid caliph-imam al-Mustanṣir died in 487/1094. In the dispute over al-Mustanṣir's succession, Ḥasan upheld the cause of Nizār and severed his relations with the Fāṭimid regime and the daʿwa headquarters in Cairo which had lent their support to al-Mustaʿlī. By this decision, Ḥasan-i Ṣabbāḥ founded the independent Nizārī Ismāʿīlī daʿwa on behalf of the Nizārī imam (who was then inaccessible).

The Nizārī state, centred at Alamūt and with territories scattered in different parts of Persia and Syria, lasted for some 166 years until it collapsed in 654/1256 under the onslaught of the Mongol hordes. This initial phase in Nizārī history was marked by numerous political vicissitudes. A superb organizer, Ḥasan-i Ṣabbāḥ designed a revolutionary strategy against the Saljūq Turks, whose rule was detested throughout Persia. He did not realize his objective, but nor did the Saljūqs succeed in uprooting the Nizārīs from their numerous mountain strongholds. But Ḥasan did manage, despite countless odds, to found and consolidate an independent Nizārī state and daʿwa.