thumb|275px|[[Douglas Haig, 1st Earl Haig|Douglas Haig and Ferdinand Foch inspecting the Gordon Highlanders, 1918]]
The commanding officer (CO) or commander, or sometimes, if the incumbent is a general officer, commanding general (CG), is the officer in command of a military unit. The commanding officer has ultimate authority over the unit, and is usually given wide latitude to run the unit as they see fit, within the bounds of military law. In this respect, commanding officers have significant responsibilities (for example, the use of force, finances, equipment, the Geneva Conventions), duties (to higher authority, mission effectiveness, duty of care to personnel), and powers (for example, discipline and punishment of personnel within certain limits of military law).
In some countries, commanding officers may be of any commissioned rank, although in others the term only refers to officers in command of units of specific sizes. Usually, there are more officers than command positions available, and time spent in command is generally a key aspect of promotion, so the role of commanding officer is highly valued. The commanding officer heads the command team within the modern military hierarchy.
There are two recurring debates related to military command: the collective command thesis and civil-military relations.
While the commander is an individual, the academic debate centres on whether command is an individual act or a form of a collective. British sociologist Anthony King argued for the emergence of a command collective in Western military forces in his 2019 book Command. Others have argued against King's thesis, stating that it romanticises the collective, that contemporary commanders themselves do not understand their function in this way, or that it may be the case. Still, collective forms of command are less effective in actual combat. U.S. Marine Corps General James Mattis also disagreed with King's thesis: "I disagree if you are trying to do decision-making in boards. The enemy will dance around you". They may be informally referred to as "Skipper", though allowing or forbidding the use of this form of address is the commanding officer's prerogative.
A prospective commanding officer (PCO) is a U.S. Navy officer who has been selected for his/her own command. The term is used in correspondence or in reference to the officer before they assume command of the unit (ship, squadron, unit, etc.).
If the sailor in command of a unit is an enlisted member, rather than a commissioned or warrant officer, he or she is referred to as the "officer in charge" rather than "commanding officer". In the Coast Guard it is common for smaller cutters to be commanded by a chief petty officer.
Air Force
In the United States Air Force, the commanding officer of a unit is similarly referred to as the unit commander, such as squadron commander, group commander, wing commander, and so forth. Squadron commanders (the base unit of the United States Air Force) are usually majors or lieutenant colonels. Group commanders (made up of two or more squadrons) are usually colonels, while wing commanders may be colonels (typical wings) or generals (larger wings).
See also
- Command and control
- Staff (military)