Douglas Haig, 1st Earl Haig in the context of "Hundred Days Offensive"

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.