How does political competition among domestic actors influence foreign policy choice? Studies examining these questions often focus on the role of economic or partisan interests, and how they influence the preferences of decision makers who are subject to electoral institutions and pressures of their constituents. Less attention has been paid to how the preferences of other influential but unelected actors influence state behavior. I examine the influence of one such group by looking at how American military leaders shape decisions on military spending and force structure, while also examining how these decisions have been affected by changes to the institutions governing civil–military relations. Results indicate that military leaders occupying key positions can influence defense spending priorities in favor of their respective branches. Results also suggest the influence of military leaders has changed and is conditional upon the institutions governing the relationships between civilian decision makers and military leaders.