Hasan bin Muhammad bin Ali, surnamed al-Kahir bi-Quwatullah, or al-Kahir bi-Ahkami'l was born in 520/1126. His official name with Alamut's records was Hasan bin Muhammad, also known as Hasan I.
In Baghdad, the Abbasid caliph Muktafi (d. 555/1160) was ruling at that time, and was succeeded by caliph Mustanjid (d.566/1170). In Iran, the Seljuq sultan Muhammad I (d. 555/1160) was succeeded by Suleman Shah (d. 556/1161) and Arslan (d.571/1176). In Egypt, the Fatimid ruler al-Faiz (d.555/1160) was followed by al-Adid (d. 567/1171), the last ruler in the Fatimid descent.
The period of al-Kahir was very peaceful, because Seljuq had waged not a single war against the Ismailis. The Nizari state had been recognized by the neighbouring rulers, and the Nizari coinage was also in circulation. The dawr-i satr was almost on the verge of completion, therefore, al-Kahir pre-arranged its celebration in his own period. It appears that he intended few major changes in Alamut, and therefore, he resolved to take over the power from Muhammad bin Kiya. In 554-5/1160, al-Kahir moved to Alamut, and caused a small gathering of the faithfuls, and took the charges from Muhammad bin Kiya in a simple indoor ceremony. He also received a ceremonial oath of allegiance from Muhammad bin Kiya and the followers. He declared Muhammad bin Kiya as his vizir and hailed his valuable services. Al- Kahir made a trip round the valley of Alamut on a horse with his new vizir to inspect the administration. The Nizari state entered henceforward into a new era when an Imam began to govern both religious and temporal powers. John Malcolm writes in "History of Persia"(London, 1815, 1st vol., p. 402) that, "Muhammad (bin Kiya Buzrug) probably gave up the name of power, as he constituted himself the vizir of the prince (Imam), whom religious consideration had led him to raise to the dignity of chief ruler."
Most of the extant sources have come down to us from hostile orbits, who have drawn the conclusion that Muhammad bin Kiya Buzrug was the third ruler till 557/1162, which is not in affirmity with the Ismaili traditions. Muhammad bin Kiya held the office till 554/1160 as a third ruler, and then al-Kahir himself became the fourth ruler. Muhammad bin Kiya continued his services as a vizir from 554/1160 till his death in 557/1162.
Mustapha Ghaleb writes in "A'lam al-Ismailiyya" (Beirut, 1964. p. 244) that, "Imam al-Kahir executed the affairs of dawa and state together with great deal of intelligence and skill, whom he dealt by his own excellent hands. He issued official orders in all the Ismaili territories, informing Muhammad bin Kiya Buzrug as his hujjat and the supervisor in political and martial affairs as well." Al- Kahir also announced that, "Muhammad bin Kiya Buzrug is my dai, hujjat and special representative. Those who adhere to our doctrines should obey him unitedly in the worldly matters, and comply with his orders, and consider his instructions as if the divine revelation. None should disobey his orders, and remain steadfast therewith, and enforce it as if they are acting for me."
It is learnt that Hasan bin Sabbah had sent some dais in Iraq, but owing to the incessant raids of the Seljuq, the Ismailis of Iraq lost their contact with Alamut. The local disputes of the dais in Iraq also caused the mission inactive. According to "A'lm al-Ismailiyya"(p. 245), "Imam al-Kahir deputed his cousin and a confident dai, Abu'l Hasan Sinan bin Suleman bin Muhammad towards Basra, with an instruction to reorganize the mission works. He blessed him with guidance and advices that proved potential in complying the assignment." Dai Abu'l Hasan swept off the internal dissensions, and brought the mission of Basra under the Syrian dais.
Zahiri Faryabi was also an eminent Ismaili dai, who had been sent by al-Kahir to a chief dai, Kamaluddin Kohistani for his further training. He was then appointed for the Ismaili mission at Daylam.
Imam al-Kahir died few months after the death of Muhammad bin Kiya at the end of 557/1162 after consigning the Imamate to his son, Hasan II.
It is worthwhile to write that when al-Kahir took power in 554/1160, some misconception took place among the people residing at remote regions, mostly the non-Ismaili Muslims of Qazwin, who cultivated two false theories in the lineage of the Ismaili Imams, which are examined as under:
1. The original name of al-Kahir was Hasan bin Muhammad bin Ali and simultaneously, the son of Muhammad bin Kiya also bore the name, Hasan bin Muhammad. Both were familiar and close to the people in the vicinity of Alamut. When Muhammad bin Kiya died in 557/1162, it seems that the ignorants considered al-Kahir as his son because of knowing him as Hasan bin Muhammad. Besides the preceding, the death of al-Kahir and Muhammad bin Kiya in the same year had been regarded as the death of one character, and that too for Muhammad bin Kiya. This distorted theory had shadowed the historical character of al-Kahir, making him Hasan, the son of Muhammad bin Kiya. When this theory became annulled and ineffectual, it was brushed aside by another following theory.
2. In the second theory, the historicity of al-Kahir has been totally ignored, making his real son, Hasan Ala Zikrihi's Salam (or Hasan II) as the son of Muhammad bin Kiya. This theory makes Hasan bin Muhammad bin Kiya and Hasan, the son of al-Kahir as one and same person.
The zealots had designed the history of Alamut almost from the bits and shreds of above imponderable fictions, and contrived the theory of one Hasan, and that too not the son of al-Kahir, but the son of Muhammad bin Kiya, which are in essence against the Ismaili doctrines. It is seen that few historians have lost sight of the right picture in the genuine Ismaili traditions, and nobody tried to shift the truth, but continued to repeat the fictions, whose historicity are highly doubtful.
When an Imam and his successors offically took charge of the Alamut's rule, most of the people and the ruling powers in Iran amplified their bitter propaganda, fearing that the rulers of Alamut in Alid descent would attract a large following in Shiites Iran, and their political influence would also be threatened. The ruling powers did not need to issue any decree against the Imams, but minted a theory that Imam Hasan II was the son of Muhammad bin Kiya, incorporating it with prevalent rumours and tales. Ata Malik Juvaini's objective was to adulterate and pervert the history of the Imams, therefore, he also derived his informations from such forged accounts, and ignored the genuine Ismaili traditions. He designed quite a doubtful history at his full liberty after the destruction of genuine Ismaili works and documents by the Mongols. This is a sharp weakness of the later and modern sources, indicating a remote possibility, not a strong one.