We’ve talked about the Nizaris before; they were Persians converted by missionaries from Ismaili Egypt. Their Ismaili belief system conflated the spiritual ruler, the Imam, with the political leader, the Caliph. They rejected all Fatimid Caliphs after a certain point and believed that their leadership continued the true Imam line. As such, they were perpetually at war with both Baghdad and Cairo. They put a lot of effort into building a state in eastern Iran, but they couldn’t maintain rule over a contiguous region. Instead, they had about 50 castles, in cities or on mountains, but the Sunni Turks controlled (taxed) the land between. I suppose Nizari towns carried their taxes secretly to Alamut, the Eagle’s Nest, dodging other patrols.
With the 25th Imam, Nizari strategy had suddenly changed. The 24th Imam had married a Sunni wife who raised her son to disbelieve in his own divine appointment. So this 25th one, Jalaluddin Hasan, burned the Nizari holy books at Alamut and cursed his ancestors. In exchange, he received the official blessing of Baghdad as Emir. Was he sincere? Or was it a survival strategy of taqqiyah? If he wasn’t sincere, he sure burned a lot of books for nothing. But in any case, it meant that during the years of Mongol invasions, the Nizari fortresses were at least at peace with Baghdad, not weakened by in-house Muslim fighting too. So far, they survived.
The turncoat Imam Hassan III died in 1221, probably poisoned. His son inherited the Imamship in spite of his father’s teaching; he was a child, but with a strong vizier who set about to reverse the Sunni-ization. Sunni teachers, the Imam’s widows, and some of his other relatives all met the axe. But a general alliance with Baghdad persisted; in 1238, the Nizaris and Abbasids joined in sending an embassy to the western Christians, to see if they could form an alliance against the Mongols. It didn’t work out. Then in 1246, the Imam and Caliph traveled to the installation of Güyük Khan in Karakorum, hoping to be seen as peaceful neighboring rulers who were kind of submitting the the Mongols but not actually sending tribute.
The Mongols had many cities in the region by Möngke’s time, and those local rulers all complained about the Nizaris. The Nizaris were again openly Ismaili Shi’ites, which the Turks did not like; they were perpetual rebels in strongholds that could never quite be conquered. Hulegu Ilkhan agreed to clean out the Nizaris for them.