Why do states reform their military manpower policies? Changing military manpower systems (MMS) entails economic, social, and political costs that often prevent states from adopting reforms even when doing so would better serve the interests of the state. Nevertheless, fundamental changes to states' military manpower policies such as the U.S. decision to replace its cadre/conscript system with an all-volunteer force in 1973 occur relatively frequently, challenging the idea of institutions as enduring, or "sticky," entities that are difficult to transform or destroy.

This dissertation examines the connecting logic in the relationship between domestic politics and changes in states' military manpower policies. Previous studies have explored the links between MMS changes and factors such as demographics, socio-cultural and economic changes, and security considerations; however, they have not fully examined how, or under what conditions, these policy changes are likely to occur nor demonstrated that these factors influence states' military manpower policies directly rather than through their effects on domestic political processes. This study improves upon existing literature by offering a theoretical model that connects changes in elite and domestic policy preferences with MMS changes and identifies the political pathways to MMS reform. While acknowledging the influence of security, economic, and socio-cultural factors in shaping the domestic political landscapes in which MMS changes occur, this research suggests that MMS reforms are best explained by changes in government leaders' policy preferences or in the preferences of the members of their winning coalitions.

Using process tracing and structured analysis guided by explicit research questions, I examine four MMS reforms in three states over various time periods in the post-World War II era: Argentina (1983--1995); Qatar (1971--2018), and Sweden (1994--2018). Each of these cases strongly support the model's predictions and suggest that changes in domestic political environments, rather than economic, demographic, or security considerations, best explain why MMS changes occur. As an important component of states' security policies, understanding why and under what conditions states reform their military manpower systems helps inform our understanding of how states design and implement national security strategy and may provide insights to explain changes in domestic and foreign policy more broadly.