Battalion
In military terminology, a battalion consists of two to six companies typically commanded by a lieutenant colonel. The nomenclature varies by nationality and by branch of arms, e.g. some nations will organize their infantry into battalions but call similarly sized units of cavalry, reconnaisance, or tanks a squadron instead. There may even be subtle distinctions within a nation's branches of arms, such a distinction between a tank battalion and an armored squadron, depending on how the unit's operational role is perceived to fit into the army's historical organization.A battalion is potentially the smallest military unit capable of independent operations (i.e. not attached to a higher command), but is usually part of a regiment or, in the United States Army, a brigade. Battalions are ordinarily homogeneous with respect to type, i.e. an infantry battalion or a tank battalion, though there are occasional exceptions.
Three to four battalions form a brigade.
In the 1960s to the present day, a typical infantry battalion has five companies: Headquarters and Headquarters Company (HHC), which includes the battalion staff; A, B, and C Companies, and a Combat Support Company, which includes scouts, anti-tank, and mortar sections or platoons.
American Army mechanized infantry battalions and tank battalions, for tactical purposes, will cross-post companies to each other, forming a battalion-sized task force (TF).
During the American Civil War a battalion was a tactical formation consisting of half the companies in a regiment.United States Army