Despite the widely different leadership styles of Donald Rumsfeld and Robert Gates, intrusive monitoring actions taken by both Secretaries of Defense have negatively affected civil-military trust relationships in the United States. While many discussions of civil-military relations center on a coup d’état, the direct seizure of political power by the military or overthrow of government by the military, this does not appear to be a realistic threat in the United States today. Rather, the challenge for civil-military relations in the twenty-first century is a growing mistrust between elected civilian leaders and the military. Actions by the military such as leaking information, performing end runs around a policy decision, and foot-dragging in carrying out actions contribute to this growing mistrust. Actions by civilian leaders such as inserting themselves in the military leaders’ day-to-day business, requiring excessive reporting, and conducting invasive investigations or audits also contribute to the growing mistrust. To address the civil-military relations challenge of the twenty-first century, this paper will review the history of civil-military relations, then briefly examine the theories from Huntington and Janowitz before turning to an in-depth analysis of Feaver’s agency theory.