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13 What were the organization and strengths of various units in the armies? (U.S. Civil War: Battles and fighting forces)


This article is from the U.S. Civil War FAQ, by Justin M. Sanders jsanders@jaguar1.usouthal.edu with numerous contributions by others.

13 What were the organization and strengths of various units in the armies? (U.S. Civil War: Battles and fighting forces)

[Compiled with the assistance of Stephen Schmidt
<schmidsj@unvax.union.edu> and Dominic J. Dal Bello

(A good source of information is Richard Zimmermann, _Unit Organizations
of the Civil War_.)

First, always remember that most Civil War units in the field were only
at anywhere between 20% to 40% of their full strength. Thus, while in
theory a company contained 100 men, and would be recruited at that size,
by the time they reached the army they'd be down to 60 or so and after the
first battle down to 40 or so. The full-strength sizes are given below, so
remember to knock them down by 50% or more when reading about units
engaged in battles.
Second, due to casualties among the officers, frequently units would
find themselves commanded by an officer one or two grades below the rank
he should have for the job (e.g., a regiment commanded by a lieutenant
colonel or major).
Third, keep in mind that in the early stages of the war and in the more
remote areas (such as the Trans-Mississippi), unit organizations tended to
deviate more from the norm. What follows will be the ideal, your mileage
may vary.

I. Infantry.

The basic unit is the company, commanded by a captain
100 men = 2 platoons = 4 sections = 8 squads
A company has the following officers (commissioned and non-coms):
Captain (1), 1st. Lieut. (1), 2nd. Lieut. (1)
1st Sgt. (1), Sgts. (4) and Corporals (8).
When the company was divided into platoons, the captain commanded one and
the 1st Lt. the other. There was a sergeant for each section, and a
corporal for each squad. The 1st Sgt. "ran" the whole company.

Battalions and regiments were formed by organizing companies together.
In the volunteers (Union and Confederate), 10 companies would be organized
together into a regiment. The regiment was commanded by a colonel. A
regiment has the following staff (one of each):
Col.; Lt. Col.; Major; Adjutant (1st Lt); Surgeon (maj.);
Asst Surgeon (capt.); Quartermaster (lieut); Commissary (lieut);
Sgt-Major; Quartermaster Sgt.
There were also volunteer organizations containing less than 10 companies:
if they contained from 4-8 companies, they were called battalions, and
usually were commanded by a major or lieutenant colonel.
The (Union) Regular regts organized before the war (1st-10th) were 10
company regiments like the volunteers. When the NEW Regular regts. were
authorized, a different organization was used. The new Regular regts were
organized 8 companies to a battalion and 2 battalions to the regiment.
Thus new Regular regts contained 16 companies. These regiments frequently
fought as battalions rather than as single regiments. However, often the
2nd battalion could not be recruited up to strength, in which case they
fought as a single regiment.

A brigade is formed from 3 to 6 regiments and commanded by a brigadier
general. The South tended to use more regiments than the North, thus
having bigger brigades. At some times in the war, some artillery would be
attached to the infantry brigade: see the Artillery section below. Each
brigade would also have a varying number of staff officers.

A division is commanded by a major general and is composed of from 2 to
6 brigades. In the North usually 3 or 4, but in the South normally 4 to 6.
Thus, a Southern division tended to be almost twice as large as its
Northern counterpart, if the regiments are about the same size. At some
times in the war, some artillery or, less often, cavalry might be
attached: see the Cavalry and Artillery sections below. Each division
would also have a varying number of staff officers.

A corps is commanded by a major general (Union) or a lieutenant general
(Confederate) and is composed of from 2 to 4 divisions. Again the North
tended to have 2 or 3, while the South had 3 or 4. Each corps would also
have a varying number of staff officers.

Corps within a geographic department were aggregated into armies. The
number of corps in an army could vary considerably: sometimes an army
would contain only 1 corps and other times as many as 8. Armies were
commanded by major generals in the North, and usually by full generals in
the South. Corps and armies usually had some artillery and cavalry
attached: again, see below. Each army would also have a varying number of
staff officers.

To summarize, the nominal strengths and commanding officers were:

 UNIT       MEN  Commander  Example NAME
 Company    100  Captain    Co. A (but not J, looks like I)
 Regiment  1000  Colonel    5th N.Y. Infantry
 Brigade   4000  Brig Genl  3rd Brigade (US) **
 Division 12000  Maj. Genl  Cleburne's Division (CS) **
 Corps    36000  Maj. Genl* IIIrd Corps (US) **
 Army            Maj. Genl+ Army of Tennessee (CS) ++
  * or Lt. Gen. in the South
  + or Gen. in the South
  ** Numerical designation was used in the North, the Commander's
     name was typically used in the South, e.g. Forrest's Corps. 
  ++ The South mainly used the name of the area or state where the
     army operated.  Rivers were used primarily as names in the
     North, e.g. Army of the Cumberland. 

II. Cavalry.

The basic unit is the troop or company, organized pretty much the same
way as an infantry company. The nominal strength was 100. If the troop
dismounted for battle, 1 man in 4 would stay behind to guard the horses.

In the Union volunteers, 12 cavalry troops form a regiment commanded by
a colonel. The Confederate Cavalry used a 10 company regiment. Again, the
(Union) Regulars had a different organization: in the Regular units 2
troops form a squadron, 2 squadrons form a battalion, and 3 battalions
form a regiment. And again, there were groups of 4-8 companies of
volunteer cavalry which are called battalions.

Initially, each Union cavalry regiment was assigned to an infantry
division. The Confederates brigaded their cavalry together. The Union
eventually adopted this organization as well. As the war progressed, both
sides formed cavalry divisions (again the South took the lead). The North
also formed cavalry corps, and the South later also adopted this

III. Artillery.

The basic unit of artillery is the battery, which has 4 to 6 guns, is
commanded by a captain, and has 4 lieutenants, 12 or so noncoms, and 120
or so privates. It typically had 4 guns in the South and 6 guns in the
North. Batteries were a subdivided into gun crews of 20 or so, and into
sections of 2 gun crews, 2 or 3 sections per battery. A gun crew was
commanded by a sergeant and a section by a lieutenant.

At the start of the war, each side assigned one battery attached to
each infantry brigade, plus an artillery reserve under the army commander.
By mid-1862, larger organizations were used. The basic unit contained 3
or 4 batteries of artillery; it was called a battalion in the South and a
brigade in the North (same unit, just a different name) and it was
commanded by a colonel, lieutenant colonel, or major.

After 1862, it was typical for each infantry division to have an
artillery battalion attached, and each corps or army to have a reserve of
two to five battalions. Each division's artillery usually fought along
side the infantry, while the corps/army reserves were used to form the
massed batteries. The artillery reserve was commanded by a brigadier
general or colonel.

IV. Other Units.

The Confederacy organized a number of units known as legions. They were
mixed-arms units, usually containing 6-8 companies of infantry, 2-3
companies of cavalry, and a couple artillery pieces. Generally as soon as
they reached the battlefield they were broken apart, the infantry forming
a battalion, the cavalry being reassigned to some other unit, and the
artillery joining the reserve. Sometimes the infantry retained the name
legion, more frequently it got renamed to battalion.

Both sides had a rudimentary Marine Corps which fought along the
Atlantic coast. The US Marines contained about 3,000 men and were
organized into companies. There doesn't seem to have been any organization
higher than that: they rarely operated in larger units than a few
companies anyway. The Confederate Marines had a strength of about 300 men
organized in four companies and was nominally commanded by a colonel.

The Union organized some "heavy artillery" units, regiments containing
10 artillery batteries (about 1800 men) which had training both as
infantry and as artillerists. They were organized in much the same way as
infantry units, but were quite a bit larger to provide enough men to run
the guns. Originally raised to man the defenses of Washington, in 1864
they joined the Grant's army, and then served more as infantry.

Both sides raised special regiments of engineers. They were organized
similarly to the infantry regiments and were expert in building forts,
entrenchments, bridges, and similar military construction. They were
combatants but usually didn't do any fighting, instead continued to work
on construction even when under fire.

Both sides raised special sharpshooter units. The Confederate units
tended to be independent companies, but the Union raised two sharpshooter
regiments (Berdan's 1st and 2nd US Sharpshooters). These regiments were
organized as infantry. Usually they were assigned to skirmish duty, or
they would be allowed to roam around the battlefield to find good
positions from which to shoot at enemy officers in the rear.


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