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.
Due to the increasingly significant socio-economic issues, the decentralization of the Seljuk government leading to inefficient army mobilization, and a unifying factor of religion in the provinces facilitating the swift spread of the revolt and a strong sense of community within Isamilis, the Seljuks were unable to quickly put down the revolt.
The conflict was characterized by the weaker Nizaris employing impregnable strongholds and assassinating key opponents (for which they gained the designation of Assassins), and the Seljuks massacring the Ismailis and their sympathizers.
Due to the Seljuks and Nizaris being unable to complete the war quickly, the Nizaris lost their momentum in the war leading to a stalemate on both sides. Combined with the Nizaris confined to heavily defended castles in unfavorable terrain, the Seljuks reluctantly accepted the independence of the Nizari state.
Background
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. The Fatimids were adherents of Ismailism, a branch of Shia Islam, and the Seljuks were Sunni Muslims.
By the final decades of the imamate (leadership of the Ismaili Muslim community) of the Fatimid caliph al-Mustansir Billah (r. 1036–1094), many people in Seljuk-ruled Persia had converted to the Fatimid doctrine of Ismailism, while the Qarmatian doctrine was declining. 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. The Chief Da'i in the 1070s was Abd al-Malik ibn Attash, a Fatimid scholar who was respected even among Sunni elites. He led a revolt in 1080 provoked by the increasingly severe Seljuk repressions of the Ismailis.
History
Establishment of the Alamut State
The Ismailis in Persia, including Da'i Hassan-i Sabbah, were aware of the declining power of the Fatimids during the final decades of the imamate of al-Mustansir. Hassan was a new Ismaili convert who had been appointed to a post in the da'wah organization by Ibn Attash in May–June 1072. Within nine years of his missionary activity in several Seljuk provinces, Hassan had evaluated the strengths and weaknesses of the Seljuk military and government and took note of the Seljuk administrative and military prowess. 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.
By 1087, Hassan had chosen the inaccessible castle of Alamut, located in the remote area of Rudbar (nowadays called "Alamut") in northern Persia, as the base of operations. From Damghan and later Shahriyarkuh, he dispatched several da'is to convert the locals of the settlements in the Rudbar valley near the castle. These activities were noticed by the Seljuk vizier Nizam al-Mulk, who ordered Abu Muslim, the governor of Rayy, to arrest the da'i. Hassan managed to remain hidden and secretly arrived at Daylam, temporarily settling in Qazvin. He was later appointed as the Fatimid Da'i of Daylam.
From Qazvin Hassan dispatched one further da'i to Alamut. Meanwhile, Ismailis from elsewhere infiltrated and populated the region near Alamut. Hassan then moved to Ashkawar, and then Anjirud, gradually getting closer to the castle, and secretly entered the castle itself on the eve of Wednesday, September 4, 1090, living there for a while disguised as a children's teacher. Mahdi, the commandant of the castle, eventually discovered Hassan's identity, but he was powerless since many in the castle, including his guards, were Ismailis or Ismaili converts then. Hassan permitted Mahdi to leave peacefully and voluntarily paid him via Muzaffar, a Seljuk ra'is and a secret Ismaili, 3,000 gold dinars for the castle. The seizure of the castle marks the establishment of the Ismaili state in Persia (also called the "Alamut state") and the beginning of the so-called Alamut Period during which the Ismaili mission unfolded as an open revolt against the Sunni authorities.
Expansion in Rudbar and Quhistan
The Ismailis of Alamut quickly began to construct or capture (by conversion or force) new strongholds in Rudbar valley on the bank of the Shahrud river. Meanwhile, Hassan dispatched Husayn Qa'ini to his homeland, Quhistan (a barren region southwest of Khurasan), where he was more successful. The Quhistani people resented the rule of their oppressive Seljuk emir more, such that the movement spread there not through secret conversion, but an open revolt. Soon the major towns of Tun (modern Ferdows), Tabas, Qa'in, and Zuzan came under Ismaili control. Quhistan became a well-established Ismaili province governed by a local ruler, titled muhtasham, appointed from Alamut.
The areas that had been chosen by the Ismaili leaders (Rudbar, Quhistan, and later Arrajan) had several common advantages: difficult mountainous terrains, dissatisfied populations, and local traditions of Ismaili or at least Shia tendencies. Initially, the Ismailis gained support mostly in rural areas. They also received crucial support from non-Ismailis who sympathized with them due to socio-economic or political reasons. Thus, the Ismailis transformed into a formidable and disciplined revolutionary group against the staunchly Sunni Abbasid–Seljuk order that had dominated the Islamic World.
A complex set of religious and political motives was behind the revolt. The anti-Shia policies of the Seljuks, the new pioneers of Sunni Islam (see Sunni Revival), were not tolerable for the Ismailis. The early widespread Ismaili revolt in Persia was, less conspicuously, an expression of national Persian Muslim sentiment: the Persians, who had been Islamized but not Arabized, were conscious of their distinct identity in the Muslim World and viewed the Seljuk Turks (and their Turkish predecessors Ghaznavids and Qarakhanids which had put an end to the so-called Iranian intermezzo) as foreigners who had invaded their homeland from Central Asia. Seljuk rule was detested by multiple social classes. Hassan himself openly resented the Turks. The Ismaili state was the first Muslim entity that adopted Persian as a religious language.
Economic issues further contributed to the widespread revolt. 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. In contrast, the Ismaili state was dedicated to the ideal of social justice.
Early Seljuk responses
The first bloodshed perpetrated by the Ismailis against the Seljuks was possibly before the capture of Alamut. A group of Ismailis performing joint prayers was arrested in Sawa by the Seljuk police chief and were freed after being questioned. The group later unsuccessfully attempted to convert a muezzin from Sawa who was active in the Seljuk capital Isfahan. Fearing that he would denounce Ismailism, the group murdered the muezzin. The vizier Nizam al-Mulk ordered the execution of the group's leader, Tahir, whose corpse was then dragged through the market. Tahir was a son of a senior preacher who had been lynched by a mob in Kirman for being an Ismaili.
Yurun-Tash, the emir holding the iqta' of Rudbar, quickly began to harass and massacre the Ismailis at the foot of Alamut. The besieged garrison of Alamut was on the verge of defeat and was considering abandoning the castle due to a lack of supplies. 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. The Ismailis eventually emerged victorious when Yurun-Tash died of natural causes. Alamut was nicknamed baldat al-iqbāl (lit. 'the city of good fortune') after this victory.
Campaigns of Sultan Malikshah and Nizam al-Mulk
Sultan Malikshah and his vizier Nizam al-Mulk soon realized the inability of the local emirs to manage the Ismaili rebels. In 1092, they sent two separate armies against Rudbar and Quhistan. The garrison of Alamut consisted of only 70 men with limited supplies when the Seljuk army under emir Arslan-Tash invested the castle. Hassan asked for assistance from the Qazvin-based da'i Dihdar Abu Ali Ardestani. The latter broke the Seljuk line with a force of 300 men and resupplied and reinforced Alamut. A coordinated surprise attack in September or October 1092 by the reinforced garrison and allied locals resulted in a rout of the Seljuk besiegers.
While planning further anti-Ismaili campaigns, Nizam al-Mulk was assassinated on October 14, 1092, in western Persia. The assassination was performed by a fida'i sent by Hassan-i Sabbah, but it was probably at the instigation of Sultan Malikshah and his wife Terken Khatun, who were wary of the all-powerful vizier.
Meanwhile, the Seljuk army against Quhistan, led by emir Qizil-Sarigh and supported by forces from Khorasan and Sistan, was concentrating its efforts on the castle of Darah, a dependency of the major Ismaili castle of Mu'min-Abad. Sultan Malikshah died in November 1092 and the soldiers besieging Darah immediately withdrew because the Seljuk soldiers traditionally owed their allegiance only to the sultan himself. With the deaths of Nizam al-Mulk and Malikshah, all planned actions against the Ismailis were aborted.
[The assassination of Nizam al-Mulk] was the first of a long series of such attacks which, in a calculated war of terror, brought sudden death to sovereigns, princes, generals, governors, and even divines who had condemned Nizari doctrines and authorized the suppression of those who professed them.
Further Ismaili expansion and schism during the Seljuk civil war of 1092–1105
The sudden deaths of Nizam al-Mulk and Malikshah reshaped the political landscape of the Seljuk realm. A decade-long civil war began involving the Seljuk claimants and the semi-independent Seljuk emirs who constantly shifted their allegiances. Berkyaruq had been proclaimed as the ruler, supported by the relatives of Nizam al-Mulk and the new Abbasid caliph al-Mustazhir. His rivals included his half-brother Muhammad Tapar and Tutush, the governor of Syria. The latter was killed in 1095 in battle. Fighting with Muhammad Tapar, who was backed by Sanjar, was indecisive, however.
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. 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. Hassan made Alamut as impregnable as possible. Assisted by local allies, new fortresses were seized in Rudbar. In 1093, the Ismailis took the village of Anjirud and repulsed an invading force there. In the same year, a 10,000-strong army consisting mostly of Sunnis from Rayy and commanded by the Hanafi scholar Za'farani was defeated in Taliqan. Soon another raid by the Seljuk emir Anushtagin was also repulsed. As a result of these Nizari victories, the local chiefs of Daylam gradually shifted their allegiance to the nascent Alamut state. Among these was a certain Rasamuj who held the strategic Lamasar castle near Alamut. He later tried to defect to Anushtagin, but in November 1096 (or 1102, per Juwayni) an Ismaili force under Kiya Buzurg-Ummid, Kiya Abu Ja'far, Kiya Abu Ali, and Kiya Garshasb attacked the castle and captured it. Hassan appointed Buzurg-Ummid as Lamasar's commandant, who expanded it into the largest Ismaili fortress.
In 1094, the Fatimid Caliph-Imam al-Mustansir died and his vizier al-Afdal Shahanshah quickly placed the young al-Musta'li on the Fatimid throne, who was subsequently recognized as the Imam by the Ismailis under Fatimid influence (i.e. those of Egypt, much of Syria, Yemen, and western India). However, al-Mustansir had originally designated Nizar as his heir. As a result, the Ismailis of the Seljuk territories (i.e. Persia, Iraq, and parts of Syria), now under the authority of Hassan, severed the already weakened ties with the Fatimid organization in Cairo and effectively established an independent da'wa organization of their own on behalf of the then-inaccessible Nizari Imams. In 1095, Nizar's revolt was crushed in Egypt and he was imprisoned in Cairo. Further revolts by his offspring were also unsuccessful. Apparently, Nizar himself had not designated any successor. Hassan was recognized as the hujja (full-representative) of the then-inaccessible Imam. Rare Nizari coins from Alamut belonging to Hassan and his two successors bear the name of an anonymous descendant of the Nizar.