Bismillahir Rahmanir Rahim.
Islamic history and forensic theology reveals that the present day renegades posing as ‘Islamic’ fighters, have all the hallmarks and characteristics of the Khawarij, who were the historical rebels and apostates of Islam. The group first came into existence at the time of the Prophet Muhammad(saw). However, their intellectual growth and ideological emergence really took root during the Caliphate of Uthman(ra) and further matured during the Caliphate of Ali(ra). According to the clear command of the Prophet(saw), their ideology and beliefs were absolutely out of the fold of Islam.
The Khawarij regarded the killing of Muslims as lawful. They rejected the authority of the Caliph and state, because they felt they were better informed of the teachings of Islam than the Caliphs, who were the most highly regarded religious authorities after the Prophet(saw). The Khawarij were renegades in every sense, believing themselves capable of governance and superior intellectual capability than the senior most religious authorities of the time. Unwilling to take instruction from the Caliph or authorities, they decided to adopt a more superior opinion that, “there is no command but that of Allah” and that they were indeed capable of making their own decisions based on this premise and did not require the assistance nor direction of either a rightly elected Caliph or an authentic religious authority. Despite claiming to practise puritanical Islam, their erroneous and misplaced ideologies rendered them out of the fold of Islam.
The Khawarij were the very first group of terrorists, who posed as Muslims, but who denounced the Islamic democracy and the fundamental tenet of Islam to follow Allah(swt), the Prophet(saw) and the people of authority; a structure recommended by the Prophet(saw) to govern a Muslim State until the end of time. They made lawful the armed struggle against and eventual assassination of Ali(ra). Since their very inception, the Khawarij have continued to hold armed uprisings and terror in the majority of Muslim states, who in turn have rejected them and their ideology as wholly out of the fold of Islam.
The Khawarij are not limited to, or were merely a group who took up arms against the rightly guided Caliphs, rather the Prophetic narrations clearly establish that groups with such actions and ideologies will emerge in every age. Though their name may differ, they are all branches of the same tree; that of the Khawarij.
And Allah(swt) alone knows best.