Second Fitna participant Yazid I
Sectarian and eschatological developments
The death of Husayn produced widespread outcry and helped crystallize opposition to Yazid into an anti-Umayyad movement based on Alid aspirations. The Battle of Karbala contributed to the definitive break between what later became the Shi'a and Sunni denominations of Islam. This event catalyzed the transformation of Shi'ism, which hitherto had been a political stance, into a religious phenomenon. To this day it is commemorated each year by Shi'a Muslims on the Day of Ashura. This period also saw the end of purely Arab Shi'ism in the revolt of Mukhtar al-Thaqafi, who mobilized the marginalized and socioeconomically exploited mawali by redressing their grievances. Before then, non-Arab Muslims had not played any significant political role. Despite its immediate political failure, Mukhtar's movement was survived by the Kaysanites, a radical Shi'a sect, who introduced novel theological and eschatological concepts that influenced the later development of Shi'ism. The Abbasids exploited the underground network of Kaysanite propagandists during their revolution and the most numerous among their supporters were Shi'a and non-Arabs.The Second Fitna also gave rise to the idea of the Islamic Messiah, the Mahdi. Mukhtar applied the title of Mahdi to Ali's son Muhammad ibn al-Hanafiyya. Although the title had previously been applied to Muhammad, Ali, Husayn, and others as an honorific, Mukhtar employed the term in a messianic sense: a divinely guided ruler, who would redeem Islam. Ibn al-Zubayr's rebellion was seen by many as an attempt to return to the pristine values of the early Islamic community. His revolt was welcomed by a number of parties that were unhappy with Umayyad rule. To them, the defeat of Ibn al-Zubayr meant that all hope of restoring the old ideals of Islamic governance was lost. In this atmosphere, Ibn al-Zubayr's role as the anti-caliph shaped the later development of the concept of the Mahdi. Some aspects of his career were already formulated into hadiths ascribed to Muhammad during Ibn al-Zubayr's lifetime—quarrels over the caliphate after the death of a caliph (Mu'awiya I), escape of the Mahdi from Medina to Mecca, taking refuge in the Ka'aba, defeat of an army sent against him by a person whose maternal tribe is Banu Kalb (Yazid I), Mahdi's recognition by the righteous people of Syria and Iraq—which then became characteristics of the Mahdi who was to appear in the future to restore the old glory of the Islamic community. This idea subsequently developed into an established doctrine in Islam.