What is the ontology of ISIS? Ulutaş takes this central question as the linchpin of his study in which he keeps a keen eye on the group’s evolution, ranging from its historical-ideological roots to its operational transformation and positioning toward other conflicting parties in the region. While placing the ISIS phenomenon into the framework of violent non-state actors (VNSA), Ulutaş discusses to what extent ISIS poses a challenge to the Westphalian system today. Dividing ISIS’ development into two phases, he focuses on the second, namely on the turning point which highlights the group’s expansion to Syrian soil.