Civilian-Military Relations

Who are the Department of Defense senior civilian leaders? We talk today with former Acting Deputy Secretary Christine Fox who has served in several administrations, and has been the second in command at the DOD. She has been the most senior female official in the history of the Department. Why is it important for a naval officer to understand the civilian-military relationship? Where is the "line" - Where do the civilian leaders "take over" from the Admirals and Generals? What is meant by the phrase, civilian authorities have the "right to be wrong"?