This research contributes new approaches and readings of the history and thought of the early Nizari Ismailis and their polity in Iran (fl. 1090-1256/483-654). Previous scholarship in the field has been satisfied with picking nuggets of information from the Ilkhanid era chronicles without much regard to the centuries-old systemic prejudices and antipathies towards the Ismailis pervasive in 13-14th/7-8th century modes of historical writing (taʾrīkh). Secondly, the difference in genre, therefore the audiences and functions of the taʾrīkh texts and their Nizari sources has rarely been given any consideration. Ismailis themselves did not write taʾrīkh. Ismaili historical writing, with few exceptions, is found in sīra (biography) and manāqib (excellences, virtues) reports included in doctrinal texts which were hagiographic in nature and used for didactic, exhortative and perhaps ritual purposes. The Ilkhanid authors moulded such texts plundered from the legendary library at Alamut into their dynastic chronicles. This dissertation is divided into two parts: the first part introduces methodological approaches and in the second part these methodologies are used to read anew the meagre sources supplemented by newly edited doctrinal treatises. Digital humanities approaches combined with double narrative analyses (DNA) methodologies are used to examine the narratives down to the semantic structures of the Ilkhanid accounts and then the story and discourse are analysed in the embedded Nizari fragments. These analyses show that the accounts of the Nizari polity based on Nizari sources in ʿAṭā Malik Juwaynī’s Taʾrīkh-i jahān-gushā completed in 1260/658 and Rashīd al-Dīn Faḍlallāh’s Jāmiʿ al-tawārīkh completed in 1310/710 became paradigms for later histories and were modelled into modern times. Numerous other new findings have been uncovered including revisions to the biographies of the Mongol wazīr Rashīd al-Dīn Faḍlallāh, author of the Jāmiʿ al-tawārīkh, Bark-Yarūq b. Malikshāh, the Saljūq Sulṭān and Ḥasan-i Ṣabbāḥ the founder of the Nizari Ismaili polity in Iran. In Part Two, the DNA approaches are used to re-read the sources to understand how after the Nizari-Mustaʿlian schism, the early Nizaris developed their eschatological and soteriological thought—from the attempts to raise Ḥasan-i Ṣabbāḥ (r. 1090-1124/483-518), the founder of the Nizari polity, as the imam, to the declaration of the Qiyāma by Ḥasan ʿalā dhikrihiʾl-salām (r. 1162-1166/557-561) and his recognition as imam. The functioning and reach of the daʿwa (summons) indicates that the conceptions of imamate and the doctrines of naṣṣ (designation of the imam), taʿlīm (authoritative teaching of the imam), satr (concealment of the imam) and kashf (manifestation of the imam) continued to significantly evolve in the Iranian context. In such discourses, the subdued voices of different Ismaili-Nizari factions and their notions of imamate have been given voice wherever possible. These re-readings also reveal that during the tumult of Saljuq era “factional sovereignties”, the Nizaris pursued multiple forms of engagement with the Saljuqs, not only conflict. Similarly, in examining the decapitation of the Nizari polity in Iran, this research focusses on Nizari-Mongol relations from the time of Chingiz Khān (r. 1206-1227/602-624) and explains their decline over the next three decades and not simply the destruction wrought by Hūlāgū b. Tuluy b. Chingiz Khān’s (r. 1256-1265/654-663) forces.