A regiment is a military unit that has been in use by the United States Army since its inception. Derived from the concept originating in European armies, a regiment was historically commanded by a Colonel and consisted ten companies for approximately 1,000 soldiers. Confusingly, the terms regiment and battalion were used interchangeably at this time; it was not until later that a battalion was defined as a sub-unit of a regiment. The regiment fulfilled both administrative and tactical functions and was the principle maneuver unit of the US Army until being superseded in the 20th century by the division.
