Military commander

The commanding officer (CO) or, if the incumbent is a general officer, commanding general (CG), 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 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. 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, and in theory, only goes to the best officers. The commanding officer is often assisted by an executive officer (XO) or second-in-command (2i/c), who handles personnel and day-to-day matters and a senior enlisted advisor. Larger units may also have staff officers responsible for various responsibilities.

In the British Army, Royal Marines, and many other Commonwealth military and paramilitary organisations, the commanding officer of a unit is appointed. Thus the office of CO is an appointment. The appointment commanding officer is exclusive to commanders of major units (regiments, battalions and similar sized units). It is customary for a commanding officer to hold the rank of lieutenant colonel, and he or she is usually referred to within the unit simply as "the Colonel" or, more commonly, the CO. "The Colonel" is usually an honorary appointment of a senior officer who oversees the non-operational affairs of a regiment. However, the rank of the appointment holder and the holder's appointment are separate. That is, not all lieutenant colonels are COs, and although most COs are lieutenant colonels, that is not a requirement of the appointment.

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