INTRODUCTION

Civil war has been by far the most common form of conflict in the international system since 1945.² Although interstate conflicts have been more lethal, in the sense that each single conflict on average generates a larger number of casualties, outbreaks of civil wars have been more frequent, and civil wars tend to be more persistent and more difficult to settle than interstate conflicts.³ In addition to the direct fatalities as a result of acts of combat, civil wars have also created large indirect costs through economics losses, and often leave severe legacies in the countries affected, which threaten to undermine the future economic and political viability of affected countries (see e.g.

Although civil wars clearly pose very severe problems for the countries where conflict takes place, intrastate conflict has traditionally not been thought of as an “international” problem or security concern. Whereas relations between states have always been a central topic in the study of conflict, much of the academic research on civil war has treated conflict within countries primarily as a “domestic” or “internal” issue, where the causes and consequences of conflict have been assumed to be confined to the country where the conflict takes place. Researchers have related civil war to various domestic explanatory factors such as a country's income (e.g.

2003), or political instability (e.g. Hegre et al.

2001). However, there are many reasons to question whether such a “closed polity” approach - where individual states are treated as isolated units, unaffected by events and actors in other states - can be appropriate for understanding civil war and the full range of their consequences. Many researchers have pointed to how civil wars often display various transnational dimensions (e.g. Brown 1993, 1996; Gleditsch 2007; Salehyan and Gleditsch 2006). The actors involved in violent civil conflicts in a given state are often linked in various ways to actors in other states. These transnational linkages imply that we will often need to look beyond individual nation states to understand why conflicts turn violent and evolve in particular ways. Furthermore, the consequences of intrastate conflicts are not necessarily limited to the individual state where violence first occurs. Violence in civil wars often crosses national boundaries, and there is an increasing recognition that conflict in one state may spread and foster violence in other states, as well as generate conflict between nation states. Moreover, the consequences of civil war may spread and affect other states through externalities of conflict such as refugees and the economic impact of conflict in neighboring countries. This in turn implies that civil war is not merely a problem for the countries experiencing conflict, but can have wide ranging security implications for other states as well. If the risk of civil wars and the prospects for their settlement are influenced by transnational factors, conflict resolution efforts are unlikely to be effective unless they consider features beyond the individual country where conflict occurs. Furthermore, the fact that interest in the outcomes and consequences of conflict often extend beyond the original conflict locations can provide help in understanding the incentives and constraints for outside actors in engaging in conflict resolution efforts.

In this chapter, I review the existing literature on the international spread of civil war and the consequences of the spread of civil war for theories of conflict and the prospects for conflict resolution. Given the limited space available here, such a review must necessarily be selective. In particular, I will not able to give full justice to the extensive literature on the causes of civil wars and their consequences within states, but will instead focus on their transnational implications and spread. To be explicit on terms, I here mean by the spread of civil war either how civil wars in one state can increase the risks of outbreaks of violence elsewhere or new conflicts involving other states, as well as conflict externalities or detrimental consequences generated by civil wars that are felt by states other than the country where the conflict initially breaks out. Since I am only focusing on the spread of ongoing civil violence, I will not discuss how international factors more generally may promote civil war, including, for example, how the global Cold War rivalry may have ignited civil wars, as seen in the Greek Civil War (e.g. Close 1993; O’Ballance 1966). Moreover, I will not cover what Lake and Rothchild (1998) call the escalation of civil wars to international actors, or cases where other states intervene on the side of government in a civil war, without the spread of the location of fighting to other states, as for example in Afghanistan (for an overview of when interventions in civil wars are more or less likely, see Regan 2000).⁴

I will first start with a brief overview of the main known empirical facts with respect to the tendency for civil conflicts to spread between states. I then proceed to discuss in more detail a series of broad classes of different forms of the spread of civil war and their consequences, with a particular focus on the mechanisms that may tie the presence of a civil war to the consequences for other states and actors.