United Kingdom In the British Army, the brigade has been the smallest tactical formation for more than two centuries, since regiments are either administrative groupings of battalions (in the infantry) or battalion-sized units (in the cavalry). A typical brigade may consist of approximately 5,500 personnel between two mechanised infantry battalions, an armored regiment, an armored artillery regiment, and other logistic and engineering units. The brigade is usually commanded by an officer holding the rank of Brigadier, who is referred to as the "Brigade Commander" (never the "commanding officer", which in the British Army is reserved for battalion-sized units). In the Royal Artillery, "brigade" was also the term used for a battalion-sized unit until 1938, when "regiment" was adopted. This was because, unlike infantry battalions and cavalry regiments, which were organic, artillery units consisted of individually numbered batteries which were "brigaded" together. The commander of such a brigade was a Lieutenant-Colonel, who was referred to as the "commanding officer".