Islamic history", unless the violation was "extreme, persistent and aggressive". According to researcher Trevor Stanley, the precedent "for the declaration of takfir against a leader" came from the medieval Islamic scholar Taqi al-Din Ibn Taymiyyah (1263–1328 CE), who supported the Mamluks in their jihad against the invading Central Asian Mongols. After the Mongols converted to Islam, another cause was sought for the jihad against them. In his famous fatwa, Ibn Taymiyyah reasoned that since the Mogols followed their traditional Yassa law rather than Sharia (Islamic law), they were not really Muslims, and since non-Muslims who called themselves Muslims were apostates, the Mongols should be killed. Ibn Taymiyya wrote that he "was among the strictest of people in forbidding that a specific person be accuse of unbelief, immorality or sin until proof from the Messenger[to this effect] has been established", yet he "regularly accused his opponents of outright unbelief and has become a source of inspiration to many Islamist and even takfiri movements." Kharijites Islamic extremism dates back to the early history of Islam with the emergence of the Kharijites in the 7th century CE. The original schism between Kharijites, Sunnis, and Shiʿas among Muslims was disputed over the political and religious succession to the guidance of the Muslim community (Ummah) after the death of the Islamic prophet Muhammad. From their essentially political position, the Kharijites developed extreme doctrines that set them apart from both mainstream Sunni and Shiʿa Muslims. Shiʿas believe Ali ibn Abi Talib is the true successor to Muhammad, while Sunnis consider Abu Bakr to hold that position. The Kharijites broke away from both the Shiʿas and the Sunnis during the First Fitna (the first Islamic Civil War); they were particularly noted for adopting a radical approach to takfīr (excommunication), whereby they declared both Sunni and Shiʿa Muslims to be either infidels (kuffār) or false Muslims (munāfiḳūn), and therefore deemed them worthy of death for their perceived apostasy. The Islamic tradition traces the origin of the Kharijities to the battle between 'Ali and Mu'awiya at Siffin in 657 CE. When 'Ali was faced with a military stalemate and agreed to submit the dispute to arbitration, some of his party withdrew their support from him. "Judgement belongs to God alone" (لاَ حُكْكْ إلَا لِلّهِ) became the slogan of these secessionists. They also called themselves al-Shurat ("the Vendors"), to reflect their willingness to sell their lives in martyrdom. These original