from the U.S. Constitution, Article 2, Section 2 (Presidential Powers):
"The President shall be Commander in Chief of the Army and Navy of the United States"
Commander in Chief is the FIRST presidential power listed. The Commander in Chief is the highest ranking officer in the military.
Imagine for a moment if CIC were an office separate from the Presidency. Military service would be an obvious mandatory requirement for the position. With that in mind, is it responsible to be considering any candidate for that office who has NEVER served in the military?