Battalion
A battalion is a large group of soldiers that consists of three or more companies [Collins English Dictionary].
Battalion is a tactical military organization composed of a headquarters and two or more companies, batteries, or similar organizations and usually commanded by a field-grade officer. The term has been used in nearly every Western army for centuries and has various meanings. In the 16th and 17th centuries, it denoted a unit of infantry forming part of a battle line and was loosely applied to any large body of men. During the Napoleonic Wars, the French developed an army organization in which the regiment was a unit of administration for its battalions, serving as fighting units in the field. In this connection, the terms regiment and battalion often were used interchangeably, but in most modern armies, the regiment is a higher unit than the battalion [Encyclopedia Britannica].
Battalion. Collins English Dictionary. Retrieved from: https://www.collinsdictionary.com/dictionary/english/battalion
Battalion. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/topic/battalion