The Commanding Officer (CO); or Officer Commanding (OC); 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, 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. Larger units may also have staff officers of various responsibilities.
Great Britain and the CommonwealthEdit
In the British Army, Royal Marines, and many other Commonwealth military and paramilitary organisations, the title of commanding officer is reserved for commanders of major units (regiments, battalions and similar sized units), almost invariably holding the rank of Lieutenant-Colonel and usually referred to within the unit simply as "the Colonel". The commanders of minor units (company, squadron or battery) are referred to as the Officer Commanding (OC). Officers and NCOs in charge of platoons, troops and sections are just referred to as Commanders (Platoon Commander, Troop Commander, Section Commander, etc).
In the Royal Air Force, the title of Officer Commanding is reserved for commanders of independent units, and commanders of wings in the Air Training Corps, e.g. Officer Commanding West Mercian Wing. COs are often referred to as "Boss."
In the Royal Navy, Commanding Officer is the official title of the commander of any ship, unit or installation. However, they are referred to as "the Captain" no matter what their actual rank, or informally as "Skipper" or even "Boss."
In the United States, the status of commanding officer is duly applied to all commissioned officers who hold lawful command over a military unit, ship, or installation.
In the United States Army, the commanding officer of a platoon is referred to as a Platoon Leader. The commanding officer of a company is referred to as a Company Commander, the commanding officer of a battalion is referred to as a Battalion Commander, and the commanding officer of a brigade is referred to as a Brigade Commander. At the division level and higher, however, the commanding officer is referred to as the Commanding General, as these officers are normally of general rank.
In the United States Navy, commanding officer is the official title of the commander of a ship, but they are usually referred to as "the Captain" regardless of their actual rank, or informally referred to as "Skipper".