A battalion is a military formation of defined size, equipment, and organization. They are usually specialized for one function, such as infantry or artillery or transportation or intelligence. Battalions will need augmentation to fight as an independent force, such as the Marine Amphibious Unit, a combined-arms striking unit built around a reinforced infantry battalion.
Infantry battalions typically have approximately 1000 soldiers; specialized battalions are often smaller. Battalions are generally commanded by a lieutenant colonel. The typical infantry battalion has three infantry companies, a heavy weapons company, and a headquarters company.