This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Hasan-i Sabbah was a Persian Nizari Ismaili leader who in 1090 seized the mountain fortress of Alamut in northern Persia, an act that founded the Nizari Ismaili state outsiders would later call the Hashshashin.
From Alamut, Hasan-i Sabbah organized the fida'i, agents trained to carry out targeted political assassinations of the state's enemies rather than commit its far smaller forces to open warfare against larger armies. Reports of these killings reached Crusader Europe as garbled legend, and it is from that legend that the English language eventually took the word assassin.
He grounded the new state's religious authority in the doctrine of ta'lim, the claim that true religious knowledge could come only through an infallible teaching Imam whose guidance the Nizari Ismailis alone possessed, rather than through independent scholarly reasoning of the kind other Muslim legal schools relied on. That doctrine gave the state built on Alamut a claim to religious legitimacy distinct from, and opposed to, the Sunni order it had seized territory from.
The 1090 capture of one mountain fortress was, in the state's subsequent history, the founding act from which everything else, the assassinations, the doctrine, the network of strongholds, followed.