A brigade is a military unit that is typically composed of two to five regiments or battalions, depending on the era and nationality of a given army. Usually, a brigade is a sub-component of a division, a larger unit consisting of two or more brigades; however, some brigades are classified as a separate brigade and operate independently from the traditional division structure. Brigades were almost always used in old wars. Traditionally, a brigade's commanding officer was a brigadier general. In most modern armies, a brigade is now commanded by a colonel.