The Contagion of the Syrian Civil War into Turkey Under the Impact of ISIS and YPG Cases: Conditioning Factors and Diffusion Mechanisms Emel Parlar Dal 1 Introduction This paper is intended to investigate the contagion of the Syrian civil war into Turkey with reference to two VNSAs: ISIS and the YPG. In doing so, the rise and transformation of violent non-state actors (VNSAs) in the realm of the Syrian civil war will not be addressed as a stand-alone trend but will rather analyze their changing role in and impact on the Syrian civil war in light of the conditioning factors and diffusion mechanisms of this conflict. The paper thus draws on the assumption that conflicts easily diffuse to neighboring states and regions under specific conditions and by direct or indirect diffusion mechanisms. The diffusion of civil wars is, therefore, a multifactorial process which must be assessed in terms of its catalyzing conditions and its mechanisms of diffusion. Such a twofold analysis of the diffusion of the Syrian civil war into Turkey provides a robust framework to examine the complete Syrian picture. In the first part of this chapter, the background of the diffusion of the Syrian civil war will be discussed using four mass-level conditioning factors: structural, political, economic-social, and cultural/percep- tional. In the second part, the conflict’s direct and indirect diffusion mechanisms will be used to investigate their various effects on Turkey via ISIS and YPG. Given this background, the main research question asks under which condition- ing factors and by which diffusion mechanisms have the Syrian civil war has spread to Turkey between 2011 and 2016 via ISIS and the YPG. Additionally, this paper also seeks to examine in which ways and under the influence of which driving conditions and mechanisms did ISIS and the YPG impact the contagiousness of the Syrian conflict in the Turkish case. The diffusion of civil wars or conflicts and E. Parlar Dal (*) Faculty of Political Sciences, International Relations Department, Marmara University, Istanbul, Turkey e-mail: emelparlar@yahoo.com © Springer International Publishing AG 2018 O ¨ .Z. Oktav et al. (eds.), Violent Non-state Actors and the Syrian Civil War, DOI 10.1007/978-3-319-67528-2_11 211