In 624/1227, Chenghiz Khan conquered eastern region of Iran, but the Ismailis of Kohistan were unaffected by the initial phase of the operations and continued to enjoy their prosperity. On that juncture, an increasing number of the Sunni Muslim refugees, including numerous ulema of Khorasan, had ferruled asylum in the Ismaili towns of Kohistan. The Ismailis welcomed the flood of the refugees, and assisted them with their own resources. In Kohistan, the Ismailis maintained an island of prosperity and stability from which all benefited. The visiting Sunni jurist and historian, Minhaj Siraj Juzjani (d. 685/1286), who spent his earlier years in the services of the Ghorid dynasty in India. He visited Kohistan three times between 621/1224 and 623/1226. He writes in his 'Tabaqat-i Nasiri' (comp. 658/1260) that Shihabuddin bin Mansur Abul Fateh, the learned Ismaili governor of Kohistan was lavish in his treatment to these Sunni refugees in his mountain fastnesses. He further writes in 'Tabaqat-i Nasiri' (tr. by Ghulam Rasul Maher, Lahore, 1975, 2nd vol., pp. 230-31) that, 'I found him a person of infinite learning with wisdom, science, and philosophy, in such wise, that a philosopher and sage like unto him there was not in the territory of Khorasan. He used greatly to cherish poor strangers and travellers; and such Muslims of Khorasan as had come into proximity with him he was wont to take under his guardianship and protection. On this account his assemblies contained some of the most distinguished of the ulema of Khorasan; and he had treated all of them with honour and reverence, and showed them much kindness. They stated to this effect, that, during those first two or three years of anarchy in Khorasan, one thousand honorary dresses, and seven hundred horses, with trappings, had been received from his treasury and stables by ulema and poor strangers.'
It is however recounted that the local Ismailis of Kohistan lodged complaints to Alamut about the negative effects of the generous hospitality from the state treasury. Thus, Shihabuddin was summoned at Alamut, and a new governor, Shamsuddin Hussain Ikhtiyar was appointed instead. The latter also came to be equally admired by the Muslim refugees because of the similar lavish treatment, which evidently implies that the principal cause of the replacement was not the lavish treatment, but was summoned for some other task. Shihabuddin himself was also a learned scholar, and his one scribe in Kohistan, called Ra'is al-Hasan bin Saleh Munshi Birjandi, had compiled the Ismaili history which was used by Rashiduddin in 'Jamiut Tawarikh.'