The end of the Cold War has given rise to the number of non-state political actors such as de facto states. While scholarly attention has been given to the concept of sovereignty and to empirical analyses of de facto statehood, de facto states as influential non-state political actors remained theoretically under-studied. This dissertation tackles the research question of how an issue that de facto states causes affects the likelihood of conflict between a parent and an external state. I examine the “opportunity and willingness” pre-theoretical framework of Most and Starr (1989) in order to comprehend how de facto states cause inter-state military conflict. I argue that the process of fighting for de facto statehood and the outcome of becoming a de facto state both create opportunity for the parent and external states. Moreover, internal dynamics in a state are important to understand whether the states are willing to exploit the interaction opportunity de facto states generate. I especially examine regime type and levels of democracy in parent, external and de facto states and argue that when these are all democracies, v likelihood of militarized disputes decrease. Using the comparative method and most similar systems design, I analyze two cases: Kurdistan Regional Government, Iraq, Turkey and South Ossetia, Georgia, Russia. Both cases support the arguments of the dissertation. I conclude with a brief summary and implications of the findings for future scholarship.