Policymakers often trumpet the potential for third parties to stop the killing associated with civil wars, yet third parties as strategic actors also have incentives to encourage longer civil wars. We argue that in order to assess the influence of third parties on civil war duration, it is necessary to consider the interdependent nature of third party interventions as they are distributed across the set of civil war combatants. We also argue that it is important to consider the geopolitical context in which civil wars occur, rather than focusing solely on characteristics internal to these conflicts. To test our hypotheses about the impact of third parties and geopolitical factors on civil war duration, we rely on event history analysis and a sample of 152 civil wars for the period 1820–1992. We find empirical support for the idea that extremely long civil wars correspond to the equitable distribution of third party interventions—stalemates prolong wars. The analysis also indicates that separatist civil wars and ongoing civil wars in states proximate to the civil war state result in civil wars of longer duration. Finally, we find that when third parties raise the stakes of the conflict by engaging in the use of militarized force against the civil war state, the duration of these conflicts is reduced. In general, our analysis underscores the importance of modeling the interdependent and dynamic aspects of third party intervention as well as the world politics of civil wars when forecasting their duration and formulating policy.

What effect do third parties have on the evolution of civil wars? The authors argue that intervention by third parties is central to the civil war process, a process that is characterized by the duration of hostilities and the type of outcome. The authors examine empirically the effect of third-party intervention into civil wars during the period 1816—1997, using the event history framework of competing risks. From the perspective of competing risks, as a civil war endures, it is at risk of experiencing a transition to one of three civil war outcomes in our sample: military victory by the government, military victory by the opposition group, and negotiated settlement. The competing risks approach provides considerably better leverage on the dynamic qualities of civil wars and, in particular, the influence of interventions by third parties. The analysis suggests that third-party interventions can be decisive in the evolution of civil wars and that third-party interventions have a different effect on the duration than different civil war outcomes. The results show that third-party intervention decreases the time until the supported group achieves military victory. Furthermore, third-party interventions, on both the government and opposition sides, increase the time until a negotiated settlement.

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Over time, states form relationships. These relationships, mosaics of past interactions, provide political leaders with information about how states are likely to behave in the future. Although intuitive, this claim holds important implications for the manner in which we construct and evaluate empirically our expectations about interstate behavior. Empirical analyses of interstate relations implicitly assume that the units of analysis are independent. Theories of interstate interaction are often cast in the absence of historical context. In the following article we construct a dynamic model of interstate interaction that we believe will assist scholars in empirical and theoretical studies by incorporating a substantively interpretable historical component into their models of interstate relations. Our conceptual model includes both conflictual and cooperative components, and exhibits the basic properties of growth and decay that characterize dyadic relationships. In an empirical exposition, we derive a continuous measure of interstate conflict from the conflictual component of the model. We rely on Oneal and Russett's (1997) analysis of dyadic conflict for the period 1950-85 as a benchmark, and examine whether the inclusion of our measure of interstate conflict significantly improves our ability to predict militarized conflict. We find empirical support for this hypothesis, indicating that our continuous measure of interstate conflict significantly augments a well-known statistical model of dyadic militarized conflict.Our findings reinforce the assertion that historical processes in interstate relationships represent substantively important elements in models of interstate behavior rather than econometric nuisances.

Few puzzles in international relations research have received as much attention as the relationship between political regimes and interstate conflict. Here we examine a particular aspect of this puzzle: the systemic relationships between democracy, democratization, and interstate conflict. We test hypotheses aimed at exploring three dimensions of this general inquiry. First, that democracy, democratization, and war are endogenous phenomena. Second, that the relationships between these three processes vary across time with respect to their strength and direction. Lastly, that these relationships also vary spatially, paying particular attention to geographic regions. Using time-series techniques with data for the period 1816-1992, we employ Granger causality and vector auto-regression (VAR) techniques to test our hypotheses. Briefly, we find evidence confirming the endogeneity of these processes, though this endogeneity is not as extensive as we anticipated and is conditional on the spatial and temporal sample selected. Perhaps more importantly, we find evidence suggesting that the statistical strength and sign of the relationships of interest exhibit considerable spatial and temporal heterogeneity. We conclude that the regional level, rather than the global level, holds more promise for understanding the interrelationships between systemic democracy, democratization, and interstate conflict.