Director of the master's program in political science and international relations at the Faculty of Natural Sciences and Humanities. The proportion of civil wars involving external intervention has increased dramatically since the end of the Cold War. This thesis seeks to explain the relationship between these two phenomena by considering the diversity of actors involved in civil wars.
A mixed-methods approach of the Cox proportional hazards model and a case study of the Yemeni civil war demonstrate that greater actor diversity leads to longer civil wars. I would also like to thank the faculty of the Department of Political Science and International Relations.
Introduction
Most civil wars involve third-party intervention, which is one of the main factors prolonging the duration of intrastate conflict (Balch-Lindsay and Enterline 2000; Elbadawi and Sambanis 2000; Regan 2002). Protracted civil wars are also characterized by the operation of non-state actors that have recently become prominent (Cragin 2015, 312). As a result, civil wars turn into chaos in which all kinds of actors (global and regional powers, neighboring states, transnational terrorist organizations, rebel groups) fight each other.
In chapter 3, I outline how different types of actors can pursue their interests when engaging in civil wars. I then introduce the bargaining framework, which I use to explain how different types of actors influence the implementation of a negotiated settlement in civil wars.
Civil wars: who fights whom
Non-state armed groups pose a serious problem for the notion of Westphalian state sovereignty, which includes the right of a state to use force legitimately in a given territory, as suggested by Weber (Krause and Milliken 2009, 202). Most non-state armed actors today pursue economic goals by capturing state resources and engaging in illicit trade and transnational networks (Davis Krause and Milliken 2009, 204). Radical left revolutionary organizations instead seek to overthrow the existing regime and subsequently seize power.
Sectarian-based revolutionary armed NSAs also seek regime change, but they are mainly concerned with state marginalization. A civil war can be considered state if it involves a radical left-wing revolutionary organization or a sectarian-based revolutionary group seeking full control of the state.
Civil war duration in the literature
Several studies in the literature suggest that longer civil wars may be the result of the warfare itself. Rather, the inclusion of additional actors exacerbates existing problems in civil wars, be they greed, grievance, or information asymmetry. While the literature thoroughly examines the role of external interventions on the duration of civil wars by taking into account the ability of parties to negotiate or achieve military victory, it fails to take into account the modern aspects of wars that today include the combination of include various types of actors.
Therefore, this research focuses on the issues of foreign interventions and their effect on the duration of civil wars. In particular, it analyzes the role of different types of external actors who introduce their interests into civil wars.
Diversity of actors and civil war duration
The interest-based approach to civil war duration can be traced through examination of the number and types of actors involved in the conflict. The variety in types of actors involved in civil wars shows the complexity of the motives for the intervention in the conflict in the first place. This is precisely why types of actors involved in civil wars matter - they all have different and conflicting interests.
Such forms of involvement and attack in civil wars are referred to as “opportunism” in the international conflict literature discussed in detail by Walt (1996). Foreign states usually participate in civil wars by supporting one of the opposing parties. Therefore, civil wars are not limited to the confrontation between the government or the rebels, but also between the various rebel groups themselves.
First, external intervenors in civil wars may introduce additional demands and preferences, thus reducing the range of bargaining (Cunningham 2006). In this sense, the involvement of different types of actors, who by their nature have different interests, also reduces the range of bargaining in civil wars. Second, third parties to civil wars can complicate the negotiation process by increasing information asymmetries that impede a negotiated settlement.
Moreover, parties in civil wars also have incentives to misrepresent information about their capabilities and delay resolution, thus prolonging the conflict. So I'm interested in the longer duration of civil wars that is also linked to their failed termination. This results in the changing alliances that are recognized as a key feature of modern civil wars (Cunningham 2006).
The types of actors proposed in this research are important because parties in civil wars engage in different types of conflict and often against different actors. Certainly, the dynamics of interventions in civil wars have important implications for their duration, which is the main rationale of this research.
Statistical Analysis
Furthermore, for the purposes of this study, I needed to measure the number and types of actors involved in civil wars. Therefore, I assume that the greater the diversity of actors in the civil war (ranging from 0 to 4), the longer the conflict continues. In this study, I ran several Cox regression models that test the effect of the number and types of actors on the duration of a civil war (see Table 1).
For the purpose of this research, I also added the measures of number and types of actors in the core model. In models 1 and 2, both measures of number and types of actors perform as expected, as they have coefficients with negative signs. As such, I test the effect of the measures of number and types of actors together with the measures of interveners' measures.
Again, the measures of number and types of actors are negative and their coefficients are higher when we control for the measures of the intervention. This suggests that greater numbers and types of actors in civil wars prolong duration, even when actors do not have separate agendas. However, in this case, the effect of the measures of number and types of actors is tested separately, showing the comparison between conflicts with larger and lower numbers and types of actors in civil wars.
The figures show that the measures of number and type of actors involved in civil wars have a substantial effect on their duration. Therefore, it is clear that both greater number and diversity of actors in civil wars prolong their duration. Overall, the results obtained from both Table 1 and Figures 1 and 2 show that the number and types of actors involved in civil wars do influence the duration of these conflicts.

Case Study
The current civil war is not the first and even the second to be experienced in Yemen. However, the Imamate faction controlled several of the seats in the government and part of patronage. In this way, the threat of civil war was prevented in Yemen, but at the cost of significant changes in the political system and elite structure (Alley 2013, 74).
However, the initiators of the protests and opposition movements such as the Houthis and Hirak were not included in the new political system. By using his influence, Saleh attempted to undermine Hadi's regime in the hope of regaining power in Yemen. As mentioned above, the Houthis are a Shia-based rebel organization fighting for regime change in Yemen.
Regime change, which was his central theme, resonated with the main goal of the Houthis – the overthrow of President Saleh and his family from power (Clausen 2018, 561). Iran has reinforced Saudi Arabia's fears by providing rhetorical support to the Houthi movement in Yemen (Salisbury 2015). Iran, meanwhile, has increased its rhetorical and humanitarian support for the Houthis in the face of growing Saudi accusations.
It is using the situation in Yemen to its own advantage by providing support to the Houthis, whom Riyadh is trying to defeat. The movement has found support from the United Arab Emirates, which is one of the most visible external actors in Yemen, along with Saudi Arabia. In addition, the UAE has been accused of taking control of strategic territories in Yemen and its ports, which appear to be one of the busiest shipping routes in the world (Clausen 2018, 570).
Hadi, although recognized as the country's president, in reality has no power over the situation in Yemen. Terrorist groups also compete with each other for influence in Yemen thus generating
Conclusion
As such, there may be some other important explanations for the longer duration of the civil war that need to be addressed. This may be a topic for further investigation in the future which will yield critical results when tested together with the number and types of external actors. Moreover, in his study on the effect of veto players on the duration of civil wars, Cunningham (2006) uses the other statistical method called Binary Time-Series Cross-Sectional (BTSCS) analysis using logit.
However, the results of this research provide important policy implications for policy makers interested in resolving such “endless” civil wars. The international community should pay more attention to civil wars with the largest number and diversity of external actors. These policy implications stem from the fact that civil wars are complex events with multiple combatants pursuing multiple interests.
Understanding how the number and diversity of those combatants can alter the duration of civil wars is critical for both theorists and policymakers. And now he is working with Russia in hopes of gaining control of the state. Yemen, Saudi Arabia and the Gulf States: Elite Politics, Street Protest and Regional Diplomacy (with Ginny Hill) - Chatham House Briefing Paper'.