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Military Organization > United States > U.S. Army Regular Infantry Regiment, New Army (1861)

U.S. Army Regular Infantry Regiment, New Army (1861)

The following was the organization of the Regular U.S. Army Infantry Regiment (New Army) during the American Civil War and effective from 1861 to 1867.


The Regular Army was the professional core of the United States Army during the Civil War having existed before the war. However, the bulk of Union infantry regiments were part of the so-called Volunteer Army of the United States which were units that were raised and equipped by individual states but came under federal command.


New Regular Army Regiments raised in 1861 were larger than their Volunteer counterparts. The New Army Regular regiments being composed of 24 companies split into 3 battalions. Meanwhile, Volunteer Infantry Regiments (and Old Army Regular Regiments) were composed of 10 companies, with the battalion being an ad hoc formation without a permanent staff that was analogous to a half-regiment or the title for an understrength regiment.


The next level up was the Brigade, which typically controlled 3 to 5 regiments. In addition to its regiments, the Brigade would have a staff of 1 Commander (Brigadier General), 1 Aide-de-Camp (Lieutenant), 1 Assistant Adjutant General (Captain), 1 Assistant Quartermaster (Captain), and 1 Assistant Commissary (Captain).


  1. Organization​

  2. Discussion

  3. Sources

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1× Regimental Staff

  • Personnel

    • Before Sep. 1862: 4 Officers and 27 Enlisted + 2 Attached Medical

    • After Sep. 1862: 4 Officers and 3 Enlisted + 2 Attached Medical

  • 1× Commander, Colonel

  • 1× Second-in-Command, Lieutenant Colonel

  • 1× Adjutant, First Lieutenant

  • 1× Quartermaster, First Lieutenant

→ Regimental Band (before Sep. 1862)

  • 1× Drum Major 

  • 2× Principal Musicians

  • 24× Musicians

→ Regimental Band (after Sep. 1862)

  • 3× Principal Musicians

→ Attached Medical

  • 1× Surgeon, Major

  • 1× Assistant Surgeon, Captain


3× Battalions

  • Personnel: 27 Officers and 780 Enlisted each

Battalion Staff (3 Officers and 4 Enlisted)

  • 1× Commander, Major

  • 1× Adjutant, First Lieutenant

  • 1× Quartermaster, First Lieutenant

  • 1× Sergeant Major

  • 1× Quartermaster Sergeant

  • 1× Commissary Sergeant

  • 1× Hospital Steward

8× Companies (3 Officers and 97 Enlisted each)

  • 1× Commander, Captain

  • Second-in-Command*, First Lieutenant

  • Third-in-Command*, Second Lieutenant

  • First Sergeant, First Sergeant

  • Sergeants**

  • Corporals***

  • Musicians

  • 82× Privates

* Could command platoons (half-companies)

** Could lead sections (half-platoons)

*** Could lead squads (half-sections)

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The New Army Regular Infantry Regiment consisted of a Regimental Staff and 3 Battalions (24 companies total) for a total of 2,452 men, or 2.4 times larger than a Volunteer or Old Army Regular Infantry Regiment.


The Regimental Staff was light by modern standards. It consisted of a Commander (Colonel), Second-in-Command (Lieutenant Colonel), Adjutant (First Lieutenant), and Quartermaster (First Lieutenant). The Colonel and Lieutenant Colonel would lead the regiment into battle, while the Adjutant and Quartermaster were staff officers. Additionally, the regimental band within the staff consisted of a Drum Major, 2 Principal Musicians, and 24 Musicians. It seems the Regimental Band would often act as stretcher bearers in combat. The Regimental Band was reduced to just 3 Principal Musicians in September 1862.


In addition, the regiment could have 1 Chaplain attached to it upon appointment by the Regimental Commander. A Surgeon (Major) and Assistant Surgeon (Captain) were also attached to each regiment from the U.S. Army Medical Department, although field hospitals were typical at brigade or division level.


Each of the regiment’s 3 Battalions consisted of a Battalion Staff and 8 Companies each. The Battalion Staff consisted of a Commander (Major), Adjutant (First Lieutenant), Quartermaster (First Lieutenant), Sergeant Major, Quartermaster Sergeant, Commissary Sergeant, and Hospital Steward. Typically, the Quartermaster would serve at regiment-level unless the Battalion were detached from the Regiment.


The Company was the basic unit of the Army. Although Platoons, Sections and Squads existed in theory for the sake of direction and cohesion, there was no real independent movement below the Company. The Company consisted of 100 men and was commanded by a Captain.  He was assisted in directing the movement and fire of their unit by a First Lieutenant and Second Lieutenant. These Lieutenants could each lead a platoon, essentially a half-company. Each Company also had a First Sergeant who was the unit’s senior sergeant appointed by the Company Commander and whose functions were primarily administrative in nature. He acted as a liaison between the officers and the enlisted men, relayed orders, called the role, and was responsible for the property of the company. In addition, the Company had 2 Musicians.


In terms of bayonet strength, the Company had 4 Sergeants, 8 Corporals, and 82 Privates. In theory the Company could split into 2 Platoons (each led by a Lieutenant) with 2 Sections each (each led by a Sergeant) which then again had 2 Squads each (each led by a Corporal with 8 men). The Corporals and Sergeants gave the Privates an example to follow and kept the formation in line with the rest of the company, although they did not have tactical commands per se until World War I. The Company’s subdivisions were fairly fluid and wouldn’t become more permanent until the late 19th and early 20th centuries.


Typically 2 men, Sergeants when practical, in the regiment would be designated color bearers—1 to carry the national flag and 1 to carry the regimental colors. The colors, while a point of pride for regiments, also had the practical purpose of guiding the regiment on a chaotic battlefield. These men, in addition to 7 color guards, Corporals when practical, formed the Regimental Color Guard.


Non-commissioned officers ranked Sergeants and above were typically issued with Model 1840 Army Noncommissioned Officers' Swords. Officially officers of the rank of Major and above were issued the Model 1850 Army Staff & Field Officers' Sword, although cavalry sabres were often privately purchased and officers of lower rank could acquire them. The most common shoulder arm for the Union was the Springfield Model 1861 muzzle-loading rifle, although other rifles and smoothbore muskets were also commonly used.



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