Malise Ruthven on ISIS' millennialism:
Though these ideas are not given prominence in most contemporary practice, the leaders of the Syrian jihad are not the first Islamic movement to give them special weight. In 1881, for example, the Sudanese Muslim cleric Muhammad Ahmad declared himself the Mahdi, conquered Khartoum, and created a state that lasted until 1898. And in 1979, an apocalyptic movement led by several Islamist extremists brought Saudi Arabia briefly into crisis with the seizure of the Grand Mosque in Mecca and calls for the overthrow of the House of Saud; the group claimed one of its own leaders as the Mahdi.
In fact, there is a strong pedigree for this ideology in classical Islamic thought. Like Christianity, Islam seems to have begun as a messianic movement warning that the Day of Judgment was imminent. The early suras (chapters) of the Koran are filled with doomsday menace, and the yearning for a final reckoning is deeply encoded in some of the texts. A central figure in this tradition is Dajjal—the one-eyed false messiah who corresponds to the Antichrist of the New Testament. The details vary but most versions agree that the final battle will take place east of Damascus, when Jesus will return as messiah, kill the pigs, destroy Dajjal, and break the cross in his symbolic embrace of Islam.
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For jihadists, such signs are rife in the Middle East today. One of the arguments ISIS and al-Nusra put forward in their apocalyptic rhetoric is that the Bashar al-Assad regime—dominated by the minority and Shia-affiliated Alawite sect, with its killings of children and repression of Islamists—is a “sign” of this departure from fundamental Islamic values that is supposed to precede the final battle.