You can't be the president and the head of the military at the same time.
Phone conversation with Pakistani President General Pervez Musharraf; 7 November 2007; reported by CBC
The power of the executive branch is vested in the President, who also serves as Commander in Chief of the Armed Forces.
White House document explaining the role of the President of the United States
It does make one wonder how good these peoples' grip is on reality.