Command or Control: Military Experience and the Secretary of Defense

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In the relationship between military leaders and their civilian masters, the Secretary of Defense (SecDef) plays a unique role. He or she represents both the military enterprise and the non-military policymakers that control it. As a result, in civil-military relations literature the SecDef role is inconsistently categorized as sometimes military, sometimes civilian. Although this is an understandable conflation, it warrants attention. By law, the SecDef is a civilian, but he or she is required to demonstrate expertise in military matters. In some ways, the position sits in both spheres. Yet, the SecDef plays a key role in civilian control of the military, and so it is important to both draw distinctions and understand overlap. This paper examines the nuances and functions of the SecDef role, and argues that Secretaries must be successful in both the civilian and the military aspects of the job in order to provide effective civilian control of the military. Intriguingly, a variety of leaders have filled the SecDef position—from decidedly civilian ones like Ash Carter, who started his career in theoretical physics, to martial legends like George Marshall. The range includes Secretaries with combat experience, ones with long careers in the Reserves, and ones with prior appointments in the Department of Defense. Every Secretary has brought a unique level of military knowledge, connection and cultural familiarity to the office. These varied personal experiences each affected civilian control of the military in their own right. This paper provides a comprehensive new dataset covering the military experience of historical SecDefs, cross-tabbed with descriptive variables in order to better understand the background and expertise each secretary has brought to the position. Finally, the paper uses five mini case studies to analyze the effect of extensive military experience on civilian control of the military. It is the first empirical study designed to explore this effect. I find, first, that all Secretaries struggle in the role in some capacity. Additionally, I find that, a SecDef’s military experience is not a strong driver in determining whether a Secretary will enhance or degrade civilian control of the military during his or her tenure.





Harb, McKinsey Rene (2022). Command or Control: Military Experience and the Secretary of Defense. Master's thesis, Duke University. Retrieved from


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