Possible Clues:

• Military officer in overall charge (abbr)
• Abbr. that denotes 'U.S. president'
• Obama, as of Jan. 2009
• POTUS, to the military
• Overall military commander
• Head of the services, for short
• Prez
• Obama's mil. title
• Pres.'s military title
• President’s military role: Abbr