A Line officer (or otherwise termed 'officer of the line') is a military officer who participates directly in combat. Officers who are not line officers are those who are in non-direct combat specialties such as chaplains, JAG officers, supply, medical. In the United States military, line officers, regardless of rank, would in times of combat have authority over higher ranking non-line officers.
In the United States Navy, Line Officers are easilly recognised by an inverted star placed over their sleeve/shoulder stripes, or by their rank insignia on both collars. Non-Line Officers have their specialty insignia placed over their sleeve/shoulder stripes and on their right collar.
