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 of ten companies, for a total of 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fulfilled both administrative and tactical functions and was the principal maneuver unit of the US Army until being superseded in the 20th century by the division.[1]
The regiment was retained as a unit in the US Army until after World War II when the Army reorganized under the Pentomic model. In order to give soldiers a sense of unit identity, the Combat Arms Regimental System (CARS) was adopted, later replaced with the U.S. Army Regimental System (USARS). The role of the regiment is currently fulfilled by the brigade and brigade combat team.[1]