The historical importance of Dezkuh is particularly related to the activities of the Nizari Ismailis in Persia during the early Alamut period (487-654/ 1094-1256). Ismaili da‘is (missionaries) had been active in the region of Isfahan during the 11th century, and by the 460s/1170s ‘Abd-al-Malek b. ‘Attas, the chief da‘i of Persia and Iraq at the time, had established his headquarters at Isfahan. Hasan Sabbah’s seizure of Alamut in 483/1090, which marked the effective foundation of the Nizari state in Persia, further encouraged the da‘wa, or missionary activities, of Ahmad b. ‘Abd-al-Malek b. ‘Attas who had succeeded his father as da‘i of Isfahan. Ahmad, posing as a schoolmaster, gradually succeeded in converting the garrison of Dezkuh, comprised mostly of Deylami soldiers with Shi‘ite tendencies.
By 494/1100, or possibly a few years earlier, Ahmad had gained possession of Dezkuh, which he fortified like other Nizari mountain castles in Persia (Zahir-al-Din, pp. 40-41; Ravandi, pp. 155 ff.; Rasid-al-Din, 1338 S./1959, p. 120; idem, 1960, pp. 69-74; Kasani, p. 156; Mirkand, Tehran, IV, pp. 306 ff.; Hodgson, pp. 85-86; Daftary, pp. 354-55). The Nizari capture of Dezkuh was a serious blow to the Saljuqs, especially as soon afterward Ahmad b. ‘Abd-al-Malek began to collect taxes in the districts around the fortress. Accordingly, the chief focus of the anti-Nizari campaign conducted by Sultan Mohammad b. Maleksah (498-51 1/1105-18) was Dezkuh.
The sultan with a large force besieged the fortress in 500/1107, but the tactics of Ahmad, who involved the Sunnite ‘ulama’ of Isfahan in a long religious disputation, in which he argued that the Ismailis were also true Muslims, delayed the conquest for almost a year, until the ‘ulama’ had rendered their judgment. Eventually battle was joined; Ahmad and his small band of nizar fought the Saljuqs gallantly from tower to tower. In the final assault, most of the Nizari defenders of Dezkuh were killed; Ahmad was captured and later executed in Isfahan (Zahir-al-Din, pp. 41-42; Ravandi, pp. 158-161; Bondari, pp. 90-91; Ibn al-Atir, X, pp. 151-52; Ibn al-Qalanesi, pp. 151-56, containing the text of the victory statement issued on the occasion; Rashid-al-Din, 1338 S./1959, pp. 121-22; Kasani, pp. 156-57; Hodgson, pp. 95-96; Lewis, pp. 53-55: Daftary, pp. 361-62). The conquest of Dezkuh is celebrated in one of the versions of the introduction to the Bahman-nama (Storey-de Blois, V, 564-65).
Dezkuh was demolished soon after on the Sultan’s orders, as he feared its recapture by the Nizaris. The extensive ruins have been investigated and described by Caro O. Minasian (1897-1972), who was evidently the first person to identify and study the site in modern times (pp. 21-39, 52-54).