Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Arts and Sciences


Political Science

First Advisor

Dr. Daniel S. Morey


This dissertation examines the causes and conditions motivating states to discontinue supporting an ongoing military coalition operation and prematurely abandon their partners. In exploring coalition defection through a three-article dissertation, I advance three separate theoretical arguments focusing on three levels of analysis.

The first article contributes to the literature by investigating the effects of political regime types on coalition abandonment during interstate wars. I argue that anocracies are dependable wartime partners and will not abandon coalition warfare earlier than autocracies and democracies. I advance two arguments for the theory of anocratic reliability. First, leaders of mixed regimes expect severe post-defeat punishment both from the opposition and regime elites, which disincentivizes premature withdrawal. Second, anocratic leaders rely on a combination of repression and the provision of public and private goods to remain in power, which incurs substantial costs. The expected gains from victory and side payments from coalition partners motivate leaders in mixed regimes to persist in the coalition war effort. An empirical analysis of interstate wars from 1816 to 2003 lends support to the central argument that mixed regimes exhibit greater reliability as wartime partners compared to their fully autocratic and democratic counterparts.

The second article considers the link between leadership insecurity and coalition defection. Prior research focuses on domestic politics, intra-coalition challenges, and battlefield circumstances to explain defection. I build on this work by arguing that domestically insecure leaders are constrained in their capabilities to maintain military engagement overseas and are highly likely to defect from coalitions. Rebellion and coups are serious domestic threats to political leaders’ survival. Therefore, coups and severe civil wars will cause state leaders to prematurely withdraw from coalition operations to bolster their security at home. An empirical analysis of coalition defections from 1950 to 2001 lends support to the expectation that vulnerable leaders are more likely to discontinue their contribution to coalition operations and redirect capabilities inward to consolidate their hold on power. This research contributes to the literature by linking domestic conflict and leadership insecurity to coalition defection and has important policy implications. Understanding factors driving defection helps policymakers gauge their allies’ degrees of reliability.

The third article contributes to the literature by bringing together two lines of research on coalitions and alliances and has important policy implications. I argue that states unsatisfied with their current levels of security and political embeddedness with a coalition leader will not defect from ongoing coalition operations. A state’s sustained engagement in coalition operations serves as a costly signal of reliability and commitment as well as a desire for improved relations with the coalition leader that is not yet realized despite greater alignment of its security interests with the coalition leader. Using newly compiled data on cases of defection from the U.S.-led coalition in Iraq from 2003 to 2008, I demonstrate that states are less likely to defect in the face of growing costs and domestic pressures when their potential for an alliance with the United States is not fulfilled. My dissertation makes key theoretical and empirical contributions to the literature on coalitions and alliances and has important policy implications

Digital Object Identifier (DOI)