[1] In the tenth century, the Muslim World was dominated by two powers: the Fatimid Caliphate ruled over North Africa and the Levant while the Seljuk Empire controlled Persia.
Apparently, the Ismailis of Persia had already acknowledged the authority of a single Chief Da'i (missionary) based in a secret headquarters in the Seljuk capital Isfahan.
After nine years of intelligence operations, Hassan concentrated his missionary efforts in Daylam, a traditional stronghold for the minority Zaydi Shias which had already been penetrated by the Ismaili da'wa.
Hassan permitted Mahdi to leave peacefully and then paid him via Muzaffar, a Seljuk ra'is and a secret Ismaili, 3,000 gold dinars for the castle.
The new Seljuk social order was based on iqta' (allotted land), which subjugated the locals under a Turkic emir and his army that levied heavy taxes.
However, Hassan claimed that he had received a special message promising good fortune from Imam al-Mustansir Billah, persuading the garrison to continue their resistance.
[16] Exploiting this political ferment and the power vacuum that developed, the Ismailis consolidated and expanded their positions into many places such as Fars, Arrajan, Kirman, and Iraq, often with temporary help from Seljuk emirs.
[16][17] Filling the power vacuum following diminished authority of a Seljuk sultan in an area became the regular pattern of Nizari territorial expansion during these conflicts.
[22] Many new scattered strongholds were also seized, including Ustunawand in Damavand and Mihrin (Mihrnigar), Mansurkuh, and the strategic Girdkuh in Qumis, situated on the Great Khorasan Road.
However, the vigorous Nizari da'wa soon replaced the doctrine of the declining Fatimids there, particularly in Aleppo and the nearby Jazr region, such that the Syrian Musta'li community was reduced to an insignificant element by 1130.
[19] Nevertheless, the Nizari mission in Syria proved to be more challenging than in Persia: their fledgling presence in Aleppo and later Damascus was soon eliminated, and they acquired a cluster of mountain strongholds only after a half-century of continuous efforts.
The methods of struggle of the da'is in Syria were the same as those in Persia: acquiring strongholds as bases for activity in the nearby areas, selective elimination of prominent enemies, and temporary alliances with various local factions, including Sunnis and the Crusaders, to reach objectives.
The decline of the Fatimids after al-Mustansir Billah's death coupled with the aforementioned political confusion of Seljuks and the Crusader threats all urged Sunnis and Shias (including Musta'lis and non-Ismailis such as Druzes and Nusayris) to shift their allegiance to the Nizari state, which boasted its rapid success in Persia.
The authority over the upper Orontes valley was being shared between the assassinated Janah al-Dawlah, the Munqidhites of Shayzar, and Khalaf ibn Mula'ib, the Fatimid governor of Afamiyya (Qal'at al-Mudhiq) who had seized the fortified city from Ridwan.
[30][32] Ridwan died shortly after and his young son and successor Alp Arslan al-Akhras initially supported the Nizaris, even ceding the Balis fortress on the Aleppo–Baghdad road to Abu Tahir.
Soon Alp Arslan was turned against the Nizaris by Muhammad Tapar, who had just begun an anti-Nizari campaign, as well as Sa'id ibn Badi', the ra'is of Aleppo and militia (al-ahdath) commander.
Supported by Ilghazi, he managed to obtain the official protection of the Burid ruler Tughtigin, atabeg of Damascus, whose vizier al-Mazadaqani had become a reliable Nizari ally.
At this point in 1125, Damascus was under threats of the Frankish Crusaders under Baldwin II of Jerusalem, and Ismailis from Homs and elsewhere had earlier joined Tughtigin's troops and had been noted for their courage in the Battle of Marj al-Saffar against the Franks in 1126.
Al-Mazadaqani persuaded Toghtekin to give a Mission House in Damascus and the frontier stronghold Banias to Bahram, who refortified it and made it his military base, performing extensive raids from there and possibly capturing more places.
[23][9] Although their expansion had been checked by Berkyaruq and Sanjar, the Nizaris still held their ground and threatened the Seljuk lands from Syria to eastern Persia, including their capital of Isfahan.
A Seljuk siege against Takrit failed to capture the citadel after several months, but the Nizaris under Kayqubad were also unable to keep it and ceded it to an independent local Twelver Shia Arab ruler, the Mazyadid Sayf al-Dawla Sadaqa.
The Seljuks had realized the impregnability of Alamut to a direct assault, so they began a war of attrition by systematically destroying the crops of Rudbar for eight years and engaging in sporadic battles with the Nizaris.
The great movement to establish a new millennium in the name of the hidden Imam had been reduced to regional conflicts and border raids, and the Nizari castles had been turned into centers of small local sectarian dynasties.
Seljuk campaigns after Muhammad Tapar's death were mostly half-hearted and indecisive, while the Nizaris lacked the initial strength to repeat successes such as the capture of Shahdiz.
Sanjar reportedly paid the Nizaris an annual of 3,000–4,000 dinars from taxes of Qumis and allowed them to levy tolls from the caravans passing beneath Girdkuh on the Khurasan Road.
[46] In 1126, two years after Kiya Buzurg-Ummid succeeded Hasan Sabbah as the head of the Alamut state, Sanjar sent his vizier Mu'in al-Din Ahmad al-Kashi to attack the Nizaris of Quhistan with orders to massacre them and confiscate their properties.
[9][54] Other assassinations recorded during Muhammad's reign include an emir of Sanjar and one of his associates, Yamin al-Dawla Khwarazmshah (a prince of the Khwarazmian dynasty, in 1139/1140), a local ruler in Tabaristan, a vizier, and the qadis of Quhistan (in 1138/1139), Tiflis (in 1138/1139), and Hamadan (in 1139/1140), who had authorized the executions of Nizaris.
[57] After the Crusaders' failure to capture Jabal Bahra', the Nizaris had quickly reorganized under the da'i Abu al-Fath and transferred their activities from the cities to this mountainous region.
Modeled and named after the hijra (emigration) of the Islamic prophet Muhammad from Mecca to Medina, the Nizaris established headquarters called dar al-hijra in Iraq, Bahrayn, Yemen and the Maghreb.
[63] The Ismaili fortresses in Rudbar were able to withstand long sieges: in addition to the inaccessibility of the terrain, the fortifications were built on rocky heights and were equipped with large storehouses and elaborate water supply infrastructure.