United States Volunteers also known as U.S. Volunteers, U. S. Vol., or U.S.V. were military volunteers enlisted in the United States Army who were separate from the Regular Army. Starting as early as 1861 these regiments were often referred to as the Volunteer Army of the United States but not officially named (codified into law) that until 1898. Regiments and batteries became known as "Volunteers" to distinguish between state and regular army units.