The commanding officer (CO) is the officer in command of a military unit. Typically, the commanding officer has ultimate authority over the unit, and is usually given wide latitude to run the unit as he or she sees fit, within the bounds of military law. In this respect, commanding officers have significant responsibilities (for example, the use o...
In the British Army the term CO generally refired to the lieutenant-colonel in command of an infantry battalion or cavalry regiment.
Unit Commander
[n] - an officer in command of a military unit
commandant noun an officer in command of a military unit
a commander of any rank from second lieutenant to colonel.