A battalion is a military unit of around 300–1,200 soldiers usually consisting of between two and seven companies and typically commanded by either a lieutenant colonel or a colonel. Several battalions are grouped to form a regiment or a brigade.
The nomenclature varies by nationality and by branch of arms, for instance, some armies organize their infantry into battalions, but call battalion-sized cavalry, reconnaissance, or tank units a squadron or a regiment instead. There may even be subtle distinctions within a nation's branches of arms, such as 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 generally the smallest military unit capable of independent operations (i.e., not attached to a higher command), although many armies have smaller units that are self-sustaining. The battalion is usually part of a regiment, brigade, or group, depending on the organizational model used by that service. The bulk of a battalion will ordinarily be homogeneous with respect to type (e.g., an infantry battalion or a tank battalion), although there are many exceptions. Every battalion will also include some sort of combat service support, typically organized within a combat support company.
The term is Italian in origin, appearing as battaglione. The French changed the spelling to bataillon, whereupon it directly entered into German.