Terrorism is one of the most fundamental security problems of states. Developments in the historical process have also affected the nature of terrorism and terrorism has been able to revise itself over time. The complex pattern of terrorism poses a serious obstacle to a common definition. On the other hand, the effort of terrorism to internalize religion can lead to much more dangerous results in the name of the fight against terrorism. In this context, as a result of the actions that started with Al-Qaeda and continued with the Islamic State of Iraq and the Levant (ISIS), terrorism has become one of the most important dangers over the last century, following a dynamic and global dimension. In addition to providing religious references to the violent acts of ISIS, the effort to build a Sunni identity has turned the fight against terrorism into a more complex field. Therefore, analyzing the original structure and ideology of ISIS will enable to reveal the area of legitimacy that the organization wants to create through religion and religious values. As a matter of fact, it has been emphasized throughout the study that the religious references used by the organization while trying to create a field of legitimacy through religion are taken out of their real meanings. In addition, it is aimed to draw attention to the role played by the conditions of the Middle East geography in the rise of the organization in the region. As a matter of fact, these conditions provide resources that nourish the absolute existence of the spirit of ISIS.