The internationalization of internal conflicts has been seen either as imposed, as inevitable, or as resulting in further interstate conflict, but it has not been defined as the varied result of actors' strategies. I argue in this research that this is a serious omission and that in order to overcome it, it is necessary to posit a two-step question: first, if, when and why is internationalization decided? second, in case internationalization is decided, how can we account for the form it adopts? This two-step question partially suggests that in order to comprehensively understand the dynamics of civil conflicts, it is necessary to develop yet another dimension of the concept of internationalization. This new form of internationalization adds a crucial component to existing studies: the analysis of the international strategies domestic actors pursue or avoid. In other words, this new facet of internationalization would allow us to observe how the preferences and actions of domestic parties to the conflict interact with the interests of international actors and their willingness (or reluctance) to participate in domestic conflicts.

The main argument of this dissertation is that even though international and internal forces and processes shape and somehow limit the choices parties to the conflict make, and that even though international actors may and can impose their decision to internationalize, there are also other instances and forms of internationalization in which local actors or parties to the conflict may still have the agency, the ability and the space to make the decision of inviting (or not inviting) international agents to participate in their struggle. Parties' decision to internationalize is then conditioned or shaped by the international and the national contexts, but domestic actors still have a substantial amount of autonomy to decide whether or not international agents should eventually participate in their conflict and under what conditions they would eventually do so. Finally, parties internationalize in order to obtain military support or political legitimacy from international actors. In order to prove these arguments, I compare three cases of civil wars in Latin America: Colombia, El Salvador and Guatemala.