Nuruddin Muhammad, surnamed Ala, also called Ala Muhammad or Muhammad bin Hasan, was born around 550/1155 or 553/1158 in Alamut. He is also known as Muhammad II, and sometimes as Ziaruddin Muhammad. His mother related to the Buwahid family. Immediately upon his accession, he arrested Hasan bin Namavar and his relatives and sentenced them to death.
Bernard Lewis writes in "The Assassins" (London, 1967, p. 95) that, "Hasan was succeeded by his son Muhammad, who proceeded to confirm that his father and therefore he himself were descendants of Nizar, and Imams. He is said to have been a prolific writer, and during his long reign, the doctrine of the Resurrection was developed and elaborated." B. Hourcade writes that, "Hasan's son, Nur al-din Mohammad II (d. 607/1210), consolidated the work of his father, whom he pronounced the true Imam, the secret son of a descendant of Nizar who had hidden at Alamut." (cf. "Encyclopaedia of Iran and Islam" ed. by Yarshater, London, 1982, p. 800).
Ala Muhammad was greatly engaged in his interest on philosophy and esoteric doctrines. His literary output was voluminous and had compiled several books on Koranic exegesis to broach the doctrines of the Ismailis. He was well steeped in Arabic and composed many proverbs and poetry in Arabic, whose fragments had been into the memories of the Muslims in Qazwin. Few misconception had started among the Muslims during his period about the qiyama in Iran and Syria, therefore, Ala Muhammad wrote several tracts to justify the doctrines of qiyama. In his elaboration of the doctrine of qiyama, he also assigned as usual a central role to the Imam. It further implied a complete personal transformation of the Ismailis who henceforth were expected to see nothing but the Imam and the manifestation of the divine truth in him. The Imam was defined in his essence as the epiphany (mazhar) of God on earth.
The period of Ala Muhammad was longer, in which there had been no war between the Ismailis and neighbouring rules. It is possible that the Abbasid and Seljuq powers were at their downfall, and were incapable to attack the Ismaili castles.
Meanwhile, an important political change took place in Iran and other eastern lands. The Seljuqs disintegrated after Sanjar's death in 552/1157, being replaced by the Turkish amirs and generals. It must be remembered that Tughril Beg (d. 455/1063) had founded the Seljuqid empire in 447/1055 and was declined in 590/1194. This dynasty produced 15 rulers belonging to seven generations.
Towards the end of the twenfth century a new power emerged in the east. South of the Aral sea lay the land of Khawaraz in Central Asia, the seat of an old civilization, whose hereditary rulers assumed the old title of the kings as the Khwarazmshahs. In about 586/1190, the Khawarazmshah Alauddin Tekish (d. 596/1200) occupied Khorasan, thus becoming master of eastern Iran. The Khawarazmians soon came to have an impressive empire of their own, stretching from the boarders of India to Anatolia. The Seljuq dynasty came to an end everywhere except in Anatolia when Alauddin Tekish defeated Tughril III at Ray in 590/1194. The triumphant Khawarazmshah was the obvious ruler to fill the vacancy created by the Seljuqs, and in the following year, the Abbasid caliph Nasir (d. 622/1225) invested Alauddin Tekish with the sultanate of western Iran, Khorasan and Turkistan.
We come across an instance of Ustandar Hazarasf bin Shahrnush (560-586/1164-1190), the Baduspanid ruler of Rustamdar and Ruyan, who had harboured himself at Alamut. According to "Jamiut-Tawarikh" (pp. 170-173), Hazarasf had cemented his close relation with the Ismailis residing at Rudhbar and granted them few castles in his territories. When his relation deteriorated with his superior, Husam ad-Dawla Ardashir (567-602/1172-1206), the Bawandid Ispahbad of Mazandarn, he took refuge at Alamut as a result. In due course, Hazarasf raided his former territories with the help of the Ismaili fidais and killed an Alid ruler of Daylaman. He was at last arrested and killed by Ardashir in 586/1190.
The hostile Sunni rulers had maintained the tradition of occasionally massacring the Ismailis. It is reported, for instance, according to Ibn Athir (12th vol., pp. 76-7) that a bulk of people accused of Ismailism were killed in lower Iraq in the year 600/1204.