The United States and United Nations have deployed military force three dozen times in attempts to rebuild failed states in the last century but have achieved success in just 56 percent of cases. Policymakers and scholars have yet to discover reliable policy options for rebuilding failed states. This dissertation is a response to that problem. What causes the success or failure of armed international statebuilding campaigns by liberal powers? The existing literature generally argues that statebuilding outcomes are a function of statebuilders’ inputs (e.g., military deployments, international aid, or the sequencing of reconstruction programs) or of the military, political, and economic conditions in the failed state. I conduct statistical te...