A squadron, or naval squadron, is a unit of 3-4 major warships, transport ships, submarines, or sometimes small craft that may be part of a larger task force or a fleet. A squadron is usually composed of a homogeneous group of the same type of ship, such as battleship, battlecruiser, cruiser, or destroyer, or of various types tasked with a specific mission such as coastal patrol, blockade, or minesweeping. Smaller warships are usually grouped in flotillas.
A squadron is usually commanded by a flag officer such as a vice admiral or a rear admiral, but squadrons are sometimes commanded by commodores or simply the most senior captain (often the same thing), depending on the importance of the command. A large squadron will sometimes be divided into two or more divisions, each of which might be commanded by a subordinate admiral. Like a fleet, a squadron is usually, but not necessarily, a permanent formation.
There are several types of squadron:
In modern navies, squadrons have tended to become administrative units. Most navies began to abandon the squadron as a tactical formation during the Second World War. The need to provide capital ships with the anti-submarine protection of a destroyer screen and air cover from an aircraft carrier led to the increasing use of ad hoc task forces, composed of whichever ships were available for a particular operation.
A naval squadron has no direct equivalent on land, but is, perhaps, the rough equivalent in value of a Brigade.