Military Organization during the Civil War

Map Symbol
Company / Battery
100 soldiers commanded by a captain.
Companies usually had an authorized strength of 97 enlisted men, but rarely were that large. In general a company was considered full at forty or so men. Typically it was divided into squads, each with one sergeant, one corporal, and ten privates.
10 Companies (1,000 men) commanded by a colonel.
A full strength regiment consisted of 10 companies, each of 97 men and 3 officers.
  • one colonel: commanding the regiment
  • one lieutenant colonel: second in command of the regiment, and commanding a brigade or wing of the regiment
  • one major: commanding another brigade or wing of the regiment
  • one regimental surgeon: A medical doctor, equal to a captain
  • assistant surgeon(s): Usually more like a physician's assistant (number, pay and importance varied)
  • ten captains: Commanding one of ten companies (usually A,B,C,D,E,F,G,H,J & K)
  • ten lieutenants or 1st lieutenants: Second in command of the company
  • ten second lieutenants: Third in command of the company

A regiment would also have a "WOG" or Warrant Over Grade position such as farrier (took care of horses), wagoners, and adjutants (basically the regimental staff clerk). They were primarily privates who were paid slightly higher for their particular skill, and slightly outranked a common private.

During the Civil War, regiments were primarily organized by states, but there were exceptions.
4 to 6 regiments commanded by a brigadier general.
2 to 6 brigades commanded by a major general.
2 or more divisions, commanded by a brigadier or major general (USA); lieutenant general (CSA).
2 or more Corps, commanded by a major general (USA ) / general (CSA).
Military Division /
Army Group
2 or more armies, commanded by a major general (USA)

Average make-up of the infantry

Confederate States Army

unit type low high average most frequent
corps per army 1 4 2.74 2
divisions per corps 2 12 3.10 3
brigades per division 2 7 3.62 4
regiments per brigade 2 20 4.71 5

Union Army

unit type low high average most frequent
corps per army 1 8 3.71 3
divisions per corps 2 6 2.91 3
brigades per division 2 5 2.80 3
regiments per brigade 2 12 4.73 4
Source: Wikipedia - Infantry in the American Civil War

More information:
  1. Civil War Army Organization
  2. Infantry in the American Civil War
  3. Regiments of the Civil War
  4. From Regiment to President: The Structure and Command of Civil War Armies
  5. Military Structure
  6. Military leadership in the American Civil War
  7. Confederate States Army
  8. American Civil War
  9. Union (American Civil War)
  10. Confederate States of America
  1. Wikipedia: Civil War Army Organization  [Online]
  2. Civil War Trust - Regiments of the Civil War  [Online]
  3. Civil War Talk - Infantry Military Structure of the Civil War  [Online]
  4. The Library of Congress, edited by Wagner, Margaret E.; Gallagher, Gary W.; and Finkelman, Paul; Civil War Desk Reference; New York; Simon & Schuster; ©2002, pp 374-376
  5. West Point Atlas for the American Civil War  [Online]