The Ismailis have had a long and eventful history. In mediaeval times, they twice established states of their own and played important parts for relatively long periods on the historical stage of the Muslim world. During the second century of their history, the Ismailis founded the first Shia caliphate under the Fatimid caliph-imams. They also made important contributions to Islamic thought and culture during the Fatimid period. Later, after a schism that split Ismailism into two major Nizari and Mustalian branches, the Nizari leaders succeeded in founding a cohesive state, with numerous mountain strongholds and scattered territories stretching from eastern Persia to Syria. The Nizari state collapsed only under the onslaught of all-conquering Mongols. Thereafter, the Ismailis never regained any political prominence and survived in many lands as a minor Shia Muslim sect. By the second half of the eighteenth century, however, the spiritual leaders or imams of the Nizari majority came out of their obscurity and actively participated in certain political events in Persia and, then, in British India; later they acquired international prominence under their hereditary title of Agha Khan (Aga Khan).