He is the ideologue and alleged leader of the Great Eastern Islamic Raiders' Front (İBDA-C), a militant Islamist group present in Turkey. He was arrested on 29 December 1998 for allegedly trying to overthrow the constitutional order by force. Subsequently, following the İBDA-C concept of 'leaderless resistance', further attacks on banks, synagogues, churches, places serving alcohol and TV stations were claimed by groups who said they were part of İBDA-C. The bombings in Istanbul claimed 65 lives including that of the British consul general Roger Short. Mirzabeyoğlu was sentenced to life imprisonment.