Commanding officer 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 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 Convention s ) , 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 officer s of various responsibilities . United Kingdom , Canada and Australia . Army . 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 reserved for commanders of major units ( regiment s , battalion s and similar sized units ) , it is customary for a unit CO to hold the rank of Lieutenant Colonel and usually is referred to within the unit simply as " the Colonel " . However the rank of the appointment holder and the holder ' s appointment are separate . I . e . all Lieutenant Colonel ' s are not CO ' s and although most COs are Lieutenant Colonel s , that is not a requirement of the appointment . Sub - units , i . e . , company , squadron and battery , do not have a commanding officer appointed . The officer in command of a sub unit holds the appointment " Officer Commanding " or " OC " . The OC of a sub - unit is customarily a Major , though again the rank of the appointment holder and the holder ' s appointment are separate and independent of each other . In some cases independent units smaller than a sub - unit , e . g . a platoon , such as a platoon of MPs that reports directly to a formation such as a brigade will also have an OC appointed . In these cases the OC will often be a captain or even a lieutenant . i . e . where its reporting relationship is the same as that of a unit or sub - units then a platoon or smaller unit might have an OC appointed . Appointments such as CO and OC may have specific powers associated with them , sometimes by law . E . g . they may have statutory powers to promote soldiers or to hold / try certain disciplinary positions and award certain punishments . For example the CO of a unit may have the power to sentence an offender to 28 days detention , whereas the OC of a sub - unit may have the power to sentence an offender to 3 days restriction of privileges . Units smaller than sub - units , i . e . platoon s , troop s and section s are not specific appointments and officers or NCOs who fill those positions are simply referred to as the commanders / leader . e . g . Platoon Commander , Troop Leader , Section Commander / Leader , etc . Air Force . In the Royal Air Force , the title of Commanding Officer is reserved for Station Commanders or commanders of independent units . As with the British Army , the post of a commander of a lesser unit such as an administrative wing , squadron or flight is referred to as the Officer Commanding ( OC ) . Navy . 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 " . United States . 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 . Army . The commanding officer of a company , usually a captain , is referred to as the company commander ( or the battery / troop commander for artillery / cavalry ) . The commanding officer of a battalion ( or squadron of cavalry ) , usually a lieutenant colonel , is the battalion commander . The commanding officer of a brigade , a colonel , is the brigade commander . At the division level and higher , however , the commanding officer is referred to as the commanding general , as these officers hold general officer rank . Although holding command in the same sense as other officers , the individual in charge of a platoon , the smallest unit of soldiers led by a commissioned officer , typically a second lieutenant , is referred to as the platoon leader , not the platoon commander . This officer does have command of the soldiers under him but does not have many of the command responsibilities inherent to higher echelons . For example , a platoon leader cannot issue non - judicial punishment . Non - commissioned officers may be said to " have charge of " certain smaller military units . They cannot , however , hold " command " as they lack the requisite authority granted by the head of state to do so . Warrant officers in the United States armed forces are single career - track officers that can , and occasionally do , hold command positions within certain specialty units , i . e . Special Forces and Army Aviation . However , warrant officers usually do not command if a commissioned officer is present ; normally they serve as executive officer ( 2IC ) . 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 . Navy . 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 " .