2022-01-252022-01-252020https://hdl.handle.net/1920/12554This dissertation assesses the impact of legitimation on political instability where the United States intervenes to either support or remove an existing leader. Throughout its history, the United States has intervened in other states, often in the name of maintaining stability, to protect its interests. However, at the heart of political instability is a crisis of legitimacy; therefore, understanding how the United States impacts existing or installed leaders’ legitimacy and how this legitimacy impacts political instability is critical for future interventions. This dissertation analyzes 179 cases of U.S. leadership intervention from 1945-2008 and finds that despite positive advances toward rational and performance legitimation and democratization after the intervention, states in which the United States removes a leader experience higher levels of instability than failed attempts to remove a leader. Cases where the United States successfully supported an existing leader had significant increases in democratization and saw a decrease in instability over time. The quantitative analyses are complemented by cases studies of interventions in Chile (1960s-1980s), Iraq (2003), and Afghanistan (2001) to highlight specific strategies the United States takes to build or undermine legitimacy and how these efforts impact political instability.