Army Organization


While reading the battle histories on this and other sites you will see references to the various levels of organization within an American Civil War army. You will see terms like corps, division, brigade, etc. What are these organizations? How big is a brigade? Who commanded a division? Why was a Confederate corps bigger (in number of men) than a Union corps when the Confederacy had fewer troops?

This essay attempts to answer these questions.

To understand the structure of the larger elements of an army, this essay starts at the most basic units and works up from there. The organizations are split up into infantry, cavalry, and artillery unit structures.

Infantry Structures

Infantry Company

Full Strength: Union – 87 to 101 men; Confederate – 65 to 125 men

At the start of the Civil War the United States army consisted of 10 permanent, "regular army" regiments. The regiments were organized based on reforms introduced in 1855, and immediately upon the start of hostilities the army started to raise the size of these units to the maximum allowed by law. The maximum size of a company was set at 84 enlisted men. Including officers, a full strength company had 87 men.

The regular army increased its size by an additional nine regiments after the start of the war. Because the Secretary of War was overwhelmed, the organization of these units fell to Secretary of the Treasury Salmon P. Chase. Chase — along with three officers as technical advisers — designed the regiments on the French model. At full strength these units had 97 enlisted men and three officers, for an even 100 men, consisting of the commanding officer (usually a captain), a 1st lieutenant, a 2nd lieutenant, a 1st sergeant, two sergeants, eight corporals, two musicians, and 82 privates. This later organization became the new company standard for the United States Army.

The vast majority of regiments in the Union army were volunteer regiments organized in much the same way as the new model Regular Army regiments. The only difference was that volunteer regiments had an additional wagoneer, raising the full strength of a Union volunteer company to 101 men.

The Confederates followed a similar model to that of the United States Army. Newly formed Confederate regiments were supposed to have a minimum of 64 to 100 enlisted men, over and above the company's sergeants and officers.

Note that the numbers listed above were for full strength companies. Companies were usually smaller than this, due to losses from combat and disease.

A company was subdivided into 8 squads, with a corporal commanding each squad. Two squads made up a section, each section commanded by a Sergeant. Sometimes a company would split down to two platoons. When this happened, the captain would command one platoon and the 1st lieutenant would command the other. For the most part, though, squads and platoons were not widely used. This was unfortunate as the intention to do so existed before the Civil War, and the conflict showed that the 100-man company was too unwieldy to run effectively.

The companies in a regiment were usually identified by a letter, from Company A to Company K. There was no Company J as "J" looked too much like "I" and could cause confusion. Companies sometimes gave themselves colourful names, a practice that was more common in the South. For example, Company A of the 49th Virginia were called the "Marion Guard", while Company D were the "Gilmer Rifles" and Company E were "The Highlanders".

Infantry Battalion and Regiment

Full Strength: 878, 1,025, or 2,367 men
Typical Strength: usually between 300 and 500

The regiment was the basic building block of the army. While a company may be detached from a regiment for a specific duty during a battle, the regiment usually traveled and stayed together as one coherent fighting unit.

The Union had three different official regimental organizations in play during the Civil War, two organizations for regular army regiments, and one organization for volunteer regiments.

The United States Army began the war with 10 permanent regiments. These formed the core of the national army and, as a result, became part of the Union Army. Before the end of 1861 the regular army was increased in size to 19 regiments. These permanent regiments were manned by professional soldiers, and were known as "Regular Army" regiments. They were numbered sequentially in the order that they were formed, and were thus designated the 1st U.S. through 19th U.S. infantry regiments.

The first 10 Regular Army regiments, the 1st through 10th United States, consisted of a single battalion. This battalion contained 10 companies of 87 men, plus the regimental staff for a theoretical full strength of 878 men.

The last nine Regular Army regiments, the 11th through 19th United States infantry, were formed by order of President Abraham Lincoln in May of 1861 (actually Lincoln asked for eight regiments but somehow received nine). These new regiments were organized according to a recently adopted organizational model patterned after the model used in France. They consisted of three battalions of eight companies, each company totaling 100 men (see the Company listing for more details). The idea was to follow the new French model where the regiment was nothing more than an administrative organization. The actual fighting unit would become the battalion (which should be familiar to anyone studying World War II infantry tactics). In fact a single battalion in these new, larger regiments compared rather closely to an older Regular Army regiment; about 800 men in the new battalions versus 878 men in an old regiment.

These new regiments had a theoretical full strength of over 2,400 men, but none of the regiments reached this level. The 12th, 13th, 14th, 17th and 19th U.S. Infantry never formed their third battalions, and the remaining regiments — the 11th, 15th, 16th and 18th — were unable to raise a full eight companies for their third battalion. Furthermore, the 11th, 12th, and 13th U.S. didn't fully enlist enough men to fill their second battalions, either. The largest size any of these regiments achieved was 2,367 men.

A battalion was usually commanded by a major or a lieutenant colonel.

Along with the 19 Regular Army regiments, the Union raised some 1,700 volunteer regiments during the war. These volunteer regiments utilized a third organizational model. While regular army regiments were made up of professional soldiers, volunteer regiments consisted of men who volunteered to fight for only a limited amount of time. The volunteer regiments were to be disbanded at the end of the conflict (though many formed the basis of future National Guard units). Men preferred to join state volunteer regiments rather than the Regular Army regiments because service in the volunteer regiments (at least at the start of the war) was of a pre-determined term (usually 2 or 3 years), and because the men had a greater attachment to their home state.

States, civil organizations or prominent citizens would "raise" a volunteer regiment by putting out fliers or an advertisement in the newspaper asking for people to join the unit. The regiment's first commander, usually of colonel rank, was often the person who personally raised the unit. Early in the war, both north and south, regiments were allowed to vote for their commanding officer and non-commissioned officers (NCOs), but this practice was later abandoned.

Most regiments were identified with the state that raised it, each one numbered in succession. This wasn't a hard and fast rule. Some regiments were named after a town or city (the 14th Brooklyn, later renamed the 84th New York, for instance). Some regiments had two designations, one within the state and one in the army in which they served. The Union's 30th Regiment Pennsylvania Volunteer Infantry was also known as the 1st Pennsylvania Reserves. In addition to the official regimental designation, some units had their own nicknames. The 44th New York were the Ellsworth Avengers, the 140th New York was the Monroe County Regiment, and the 1st South Carolina Rifles also went by the name of Orr's Regiment of Rifles.

Because they were composed of non-professionals and raised by individual states, and because it was believed the states were more comfortable with the old organizational system, volunteer regiments were comprised of a single battalion of 10 companies. However, instead of the old 87 man company, they used the new model of company, consisting of 100 men (actually 101 men, as a volunteer regiment's company also had a wagoneer attached to it; the Regular Army regiments did not have this wagoneer). Including a staff of 15 regimental officers, a volunteer regiment had a full theoretical strength of 1,025 men. The regimental staff consisted of a colonel as a commanding officer, a lieutenant colonel, a major, an adjutant (1st lieutenant), a surgeon (major), two assistant surgeons (at least one was usually a captain), a quartermaster (lieutenant), a chaplain, a sergeant-major, a quartermaster's sergeant, a commissary-sergeant, a hospital steward, and two principal musicians.

In addition to the infantry, there were 32 heavy artillery regiments in the Union army. Most of these regiments performed garrison duty in the defenses around Washington, or in coastal defenses where heavy artillery was used. These units were trained to fight as both infantry and artillery. In the spring of 1864 most of the Washington heavy artillery regiments were moved out of their defensive positions, leaving their heavy guns behind, and used as large infantry regiments. A regiment of heavy artillery contained 1,800 men, divided into 12 companies of 150 soldiers. Each company had the same officers as an infantry company, along with an extra captain and four lieutenants. These 12 companies were organized into three battalions of four companies, with each battalion under the command of a major. There was still only one colonel and one lieutenant colonel, the same as an infantry regiment. The heavy artillery companies were large because they needed enough men to operate the company's cannons when the regiment was not utilized as infantry.

Although most of the Union volunteer regiments were raised by states, a few hundred were not. Two of them, the 1st and 2nd U.S. Sharpshooters are described in the sharpshooters listing.

Except for two regiments raised in Massachusetts, "colored" volunteer regiments — composed of African-Americans — fell under Federal service. Some of these regiments started life as state battalions. The Louisiana Native Guard, which served with the Union, was originally raised in the New Orleans area by the Confederacy. First known as the Corps d'Afrique and by other names, in the spring of 1864 they were renamed the U.S. Colored Troops. Regiments made up of native Americans (the 1st through 4th Indian Home Guards) were handled the same way. Altogether there were 138 black regiments and four native regiments. They were organized the same way as volunteer regiments, even though they were technically Federal regiments. In almost every case the officers commanding the "Colored" or "Indian" regiments were white.

In 1864, six U.S. Volunteer regiments (the 1st through 6th) were recruited from Confederate prisoners of war for service on the American frontier. They did not take part in fighting against the Confederacy. In 1865 nine regiments of U.S. Veteran Volunteers were raised from men who had already fought in the war.

Troops too wounded to fight with regular line infantry, but still capable of serving, were put in the Invalid Corps. After September, 1863, an Invalid Corps regiment consisted of six companies in the 1st battalion and four companies in the 2nd battalion. The 1st battalion consisted of men who could handle a gun and could do light marches. They were used for guard duty. The second battalion was for men who were worse off. They acted as cooks and nurses in hospitals. In March, 1864 the corps was renamed the Veteran Reserve Corps as "IC" was too often confused with "Inspected Condemned".

The Confederacy was authorized to raise a regular standing army of 15,015 men, 744 of whom were officers. The regular Confederate Army did not reach this size for the same reasons the Union's regular army was less popular than the state volunteer regiments. The vast majority of Confederate regiments were volunteer regiments, and all of them were associated with individual states.

Confederate regiments were organized much the same way as Union volunteer regiments with 10 companies per regiment. Each battalion was to have one lieutenant colonel or major, one adjutant with the rank of lieutenant, one sergeant-major, one quartermaster-sergeant, and a chief bugler or principal musician. Each company also had an additional 2nd lieutenant. These were in addition to the 64 to 100 enlisted men per company.

Sometimes volunteer battalions were raised instead of a full regiment. Occasionally a volunteer unit would consist of both a regiment and a battalion. The Confederate 66th Georgia regiment was raised in 1864 with 1,500 men, consisting of one regiment of 10 companies and an attached battalion of 3 companies. During the war the Confederacy raised 642 infantry regiments, 9 legions (see Legions, below), 163 separate battalions, and 62 unattached companies.

While the ideal maximum strength — that is, the strength "on paper" — of a Union volunteer regiment was 1,025 men, a newly raised regiment could have far more than 1,000 men. In July of 1861, the 36th Illinois regiment had 1,151 men. The 14th Indiana had 1,134 men. None of the Regular Army regiments achieved full strength due to the difficulty in getting men to enlist with the Regular Army. Men tended to enlist in volunteer regiments associated with their state instead of joining the regular army.

It didn't take long for regimental strengths on both sides of the conflict to deteriorate. Men left the regiment before battle due to disease, desertion, or because they were simply unfit for duty. Casualties in combat dropped the numbers before they could be replaced. On May 11, 1864, the 13th Massachusetts regiment could muster only 107 men. The 20th Maine had 386 men at Gettysburg (July 1 to 3, 1863) but was reduced to 80 men by late 1863. At Antietam (September 17, 1862), the 17th Virginia regiment could put only 55 men into the line.

The average regiment size floated between about 300 and 600 men. The average number of men in a regiment for the following battles were: Shiloh (April 6 - 7, 1862), 560 men; Fair Oaks (31 May-1 June 1862), 650 men; Chancellorsville (1-5 May 1863), 530 men; Gettysburg (1-3 July 1863), 375 men; Chickamauga (19-20 September 1863), 440 men; The Wilderness (5-7 May 1864), 440 men.

For most of the war there was no formal system for replacing regimental losses. New recruits usually joined new regiments. It was up to the colonel of an existing regiment to see to his own replacements, which he might do by sending a convalescing officer back to the home state, county, city, or town to do some recruiting of his own. Existing regiments usually had to compete with recruiters from new regiments. The 149th Pennsylvania (the New Bucktails) spent the fall of 1863 and winter of 1863/64 recruiting replacements for losses at Chancellorsville and Gettysburg. By the spring of 1864, the Union command took over and began putting replacements in existing regiments.

What added to the tragedy of casualties due to combat and disease was the fact that a volunteer regiment usually consisted of men from the same town, county, or part of a city. Brothers, cousins, and sometimes fathers and sons often joined the same regiment. A nasty fight could wipe out a generation of men from entire families. Many small towns found their adult male population decimated after a major battle.

During the war, regiments could cycle through hundreds of men lost due to death (combat and disease), mortally wounded (a wound that eventually killed the victim), wounded, sick, or missing. Throughout the war, the 5th New Hampshire regiment lost a total of 295 men killed or mortally wounded (this does not include men who were missing and unaccounted for, or men who were wounded and had to leave the regiment because they could no longer serve). This was the greatest number of men killed in any single infantry regiment on either side. The 1st Maine heavy artillery regiment — one of those units that was reorganized to fight as an infantry unit — lost a total of 423 men killed or mortally wounded, for the greatest death rate of any regiment in the war.

One positive aspect (if you could call it that) came from the high attrition rates among Civil War regiments. Civil War regiments were just too large and cumbersome to be effectively controlled. This led to high casualty rates among generals — who often commanded far in front in order to make the units do as they were ordered — and poor performance on the battlefield. As casualties mounted, regiments shrunk to a more manageable size.

Infantry Brigade

Full Strength: 3,000 to 6,000 men
Typical Strength: 1,000 to 3,000 men

The basic combat unit in major battles was the brigade. The brigade consisted of between 3 and 6 regiments, with Confederate brigades tending to have more regiments than Union brigades. Early in the war, an artillery battery was often assigned to a brigade.

Brigades often fought in one long battle line. Sometimes a regiment was held back from the battle line to act as a reserve.

Brigades sometimes, but not always, consisted of regiments from similar areas of the country. This is more true of the South than the North. The "Stonewall Brigade" (First Brigade, Virginia Volunteers) consisted of 5 regiments from different areas of Virginia. However, Vincent's Brigade of the Union Fifth Corps at Gettysburg consisted of regiments from New York, Pennsylvania, and Maine.

A brigade was usually commanded by a brigadier general, also known simply as a "brigadier". Casualties resulted in colonels and lieutenant colonels (and sometimes men of lesser rank) in command of a brigade during a battle. The brigade had a varying number of staff officers.

Early in the war the brigade was the highest level of organization within an army, but that soon changed. The Union army had divisions — but no corps — at 1st Bull Run/Manassas. The Confederates had two armies present at 1st Bull Run, with each army made up of brigades but no divisions or corps.

Brigades were often numbered and given formal names, but in battle reports they were usually named after their commander. Brigades also tended to keep the same regiments, thus brigades formed their own sense of honor and camaraderie. They also earned valor and distinction, usually denoted by a well-known nickname. The "Stonewall Brigade" was named after its first commanding officer, the famous Thomas "Stonewall" Jackson. Two famous Northern brigades were the Irish Brigade and the Iron Brigade (the latter was earlier known as the Black Hat Brigade). As a general rule, the North referred to brigades by their numerical designation while the South referred to them by their commander's name. In the battle reports on this site, all brigades are referred to by their commander's name or by their famous nickname.

Infantry Division

Typical Strength: 3,000 to 12,000 men

It is too difficult for an army's commanding officer to move individual brigades. In order to manage a battle more effectively, brigades were grouped into a structure known as the division. A division consisted of between 2 and 6 brigades. In the North, there were usually 3 or 4 brigades to the division. The South usually had 4 to 6 brigades in a division. Thus, with more brigades per division and more regiments in a brigade, a Confederate division was usually about twice the size of a Union division.

After 1862, it was common for a division to have an artillery battalion attached to it. Early in the war, a Union division would have a cavalry unit assigned to it, but this organization was later discarded.

A division usually went into battle with two or three brigades in front, separated by a gap for maneuvering purposes, and a brigade held back in "support" as a reserve.

A division was usually commanded by a major general, though an officer of brigadier general or lower rank often took over due to casualties. The division had a varying number of staff officers.

In general, the North referred to divisions by a numerical designation (First Division, Tenth Corps, for instance) while the South referred to them by their commander's name. Brigades were re-assigned to divisions more readily than regiments to brigades, so soldiers held little "kinship" to a specific division. In the battle reports on this site, all divisions are referred to by their commander's name.

Infantry Corps

Typical Strength: 10,000 to 40,000 men

Even with brigades split up into divisions, it was clear by mid-1862 that Civil War battles could not be adequately maneuvered and fought if the army's commander had to give orders directly to each division. In response, corps were created.

A corps (pronounced "core" if singular, "cores" if plural) was made up of, typically, 2 to 4 divisions. The Union tended towards smaller corps of 2 or 3 divisions, while the Confederacy usually incorporated between 3 and 4 divisions per corps. With the larger number of regiments per brigade and the larger number of brigades per division, a Confederate corps was often at least as big as two Union corps. For instance, at Chancellorsville in 1863, "Stonewall" Jackson had a corps of 28,000 men. He smashed into the flank of the Union Eleventh Corps under Major General O. O. Howard. The Eleventh Corps was the smallest in the Army of the Potomac, with only 11,000 men.

A corps would usually have an artillery reserve of between 2 and 5 battalions for use as massed artillery. This was over and above the artillery assigned to the divisions within a corps. Early in the war a corps would also have cavalry divisions assigned to it.

In essence, a corps existed as a self-contained miniature army capable of operating independently. The overall army commander was in charge of fighting the battle but he tended to allow his corps commanders a lot of latitude in carrying out his orders. There was just too much detail for the army's commander to micromanage divisions and brigades. When a corps commander was excellent, like "Stonewall" Jackson at Chancellorsville, the army had an incredible edge over the enemy. When the corps commander was inept, like O. O. Howard at the same battle, the army could face disaster. Since Union corps were smaller than Confederate corps, Union armies tended to be harder to manage (there were more officers to coordinate), but they also tended to be more flexible (the army's commander could move smaller chunks of the army).

In the North, a corps was usually commanded by a major general. Until October of 1862, the South didn't officially allow the formation of corps, and did not have the rank of lieutenant general necessary for commanding the corps. However, the corps structure was so important that army commanders got around this by creating informal "wings" and placing a major general in charge of them. "Stonewall" Jackson and James Longstreet were both in charge of "wings" of Robert E. Lee's Army of Northern Virginia until after the Battle of Antietam. These were corps in everything but name. In October 1862, both men were given the newly allowed rank of lieutenant general and their "wings" were formally designated as corps.

Corps were usually given a number. These numbers are usually seen in Roman numerals, so the First Corps was written as "I Corps", Eleventh Corps as "XI Corps", etc. A corps would keep its numerical designation even when it was transferred to another army. The numeric designation was used in the South, but most historical references use the commander's name. On this site, the Union corps are usually indicated with either the numeric designation or both the number and the commander's name (Howard's Eleventh Corps, for instance). Confederate corps are usually indicated with the name of the commander only.

The corps had a varying number of staff officers.

Wing or Grand Division

Typical Strength: 20,000 to 60,000 men

As mentioned above under Corps the South had wings which were corps in all but name.

The North dabbled with wings as a way of combining several corps under one commander so that the army's commanding general would have fewer generals immediately subordinate to him. A Union wing consisted of 2 or more corps under one commanding major general. The commander of the wing would then report to the general in charge of the army. Sometimes the wing's commander would be in charge of a corps as well.

Major General Burnside created "Grand Divisions" before the Battle of Fredericksburg, consisting of two or more corps. The grand division commanders received orders from Burnside and would relay their orders to the corps commanders or directly to divisional commanders. This arrangement was cumbersome and didn't work well. The intent was probably to produce something like the huge corps used by the South, but all it did was create an additional level of command between the army commander and his corps commanders. The concept was dropped by Major General Hooker when he took over in early 1863.

Hooker did use the wing idea in a modified form. He had certain corps commanders control parts of his army. These wings consisting of two or more corps. In this case, the wing commanders were more like a proxy of the overall army commander. They helped with the maneuvering and placement of units and would act as an overall battlefield commander when the commanding general was yet to arrive on the scene, but they also had command of a corps and their corps responsibilities were primary. This same structure was used throughout the Gettysburg campaign by Union Major General George Meade.

Wings were usually designated by the side of the battle line they occupied. Left Wing, Right Wing, and Center Wing are typical. The wing had a varying number of staff officers.


Corps in one area of the country were combined into armies. Armies were essentially autonomous, reporting directly to a the head of a department (a section of the country overseen by a general), a general in charge of all the armies of the nation, or the president himself.

An army could be as small as a single corps or as large as 8 corps. Sizes ranged from about 10,000 men to over 120,000 men. The number of armies fielded by either side of the war varied. The North typically had at least a half a dozen armies in the field at any one time.

Later in the war, an army would usually have an artillery reserve of between 2 and 5 battalions for use as massed artillery. This was over and above the artillery assigned to the corps and divisions within an army. During the war cavalry corps were created, and so an army would have one or more cavalry corps assigned to it.

Armies were typically named after the military department in which they were formed. These military departments were usually named after a geographic feature. Although not a hard and fast rule, the South often used the name of an area or state, and the North often used the names of rivers or states. So, you have the Union Army of the Ohio, Army of the Potomac, and Army of the Cumberland. On the other side you have the Confederate Army of Northern Virginia and Army of Tennessee. Note that at the battle of 1st Manassas/Bull Run the Confederates had an Army of the Potomac and the Union had an Army of Virginia. At 2nd Manassas, Robert E. Lee's Confederate Army of Northern Virginia fought John Pope's Union Army of Virginia.

Armies had a varying number of staff officers. Armies were commanded by major generals in the North, and by major generals or full generals (the rank simply being "general") in the South. The general in control of the army would have a number of hand picked officers to handle his paperwork and other aspects of his personal life within the army. The adjutant general was the chief of staff, and was responsible for the army's correspondence, movements, personnel administration, appointments, etc. He might keep track of operations and he might run the military intelligence branch of the army. The army wouldn't have just one staff, it would have several, and the adjutant general would co-operate with the other staffs. Some of the other staffs within an army were Cavalry, Artillery, Engineers, Topographical Engineers (map makers), and Signals staffs. The inspector general was responsible for each unit's efficiency and discipline. He was also in charge of training and doctrine, though this rarely went beyond the basic drill books. The provost marshal was the head of the military police. Under Joe Hooker the provost marshal became head of the Army of the Potomac's military intelligence agency, the Bureau of Military Information. The judge advocate was in charge of the military court. The quartermaster general looked after the army's supplies and transportation, and co-operated with Subsistence and Ordinance staffs, the Wagonmasters, the Railroad staffs, and the Medical, Postal, and Pay organizations.


Throughout the war, the Union tended to have a general in charge of all the Union armies. At the beginning of the war this man was Winfield Scott, the aging hero of the Mexican War. In 1862 the job was given to George McClellan, who maneuvered Scott out of the position. McClellan lost the general-in-chief position when he went into the field for his Peninsula Campaign. Major General Henry Halleck was given the job until 1864. Halleck did not command in the field during this time, but instead exerted control over the army commanders. In early 1864, Ulysses S. Grant became Lieutenant General (the rank given to George Washington) and was made general-in-chief of all the Union armies. Halleck was made chief of staff to make way for Grant.

When Grant was made General-in-Chief, every Union army commander reported directly to him. This included Major General George Meade, who was given command of the Army of the Potomac in late June, 1863. Unlike Halleck, Grant stayed in the field and masterminded The Overland Campaign in Virginia. So, though you will read about Grant and Lee fighting each other in Virginia, technically Grant wasn't the commander of the army facing Lee. Technically the army belonged Meade. However, Grant devised the army's strategy, and it was Grant who had the final say in what the army did. This is subtle and can cause some confusion among people new to Civil War history. It was also a cumbersome arrangement that caused problems during the Overland Campaign.

The Union were not the only ones to have a general-in-chief. Robert E. Lee was made general-in-chief of all the Confederate armies in February, 1865.

Specialty Infantry Structures


The legion was a mixed arms unit, consisting of between six and eight companies of infantry, two to three companies of cavalry and a couple of artillery pieces. They were raised much like infantry regiments, and often retained the name of the person who raised it. While legions were much more common in the Confederacy, which raised nine during the course of the war, Purnell's Legion was raised in Maryland by William Henry Purnell — the postmaster of Baltimore — and fought for the Union.

Legions were not a good fit with the rest of the army, so they were usually split up before the unit entered battle. The cavalry was moved to a cavalry unit and the artillery was moved to the artillery reserve of the army or corps. The infantry was maintained as its own unit of battalion strength. Sometimes the infantry retained the designation "legion", but more often it became known as a battalion.


In the South, sharpshooters were typically of company size. The Union created two full regiments of sharpshooters, Berdan's 1st and 2nd U.S. Sharpshooters. These two regiments were organized as infantry, though they wore green uniforms in the style of British "rifle" regiments. They were volunteers, but they were designated as a federal regiment (thus the "U.S." designation) and the regiments' officers were assigned by the federal government.

Sharpshooter regiments and companies were usually sent in front of regular infantry regiments to act as skirmishers. Sometimes they were allowed to move about the battlefield on their own. They would look for good hiding positions and act as snipers.


Both the Union and the Confederacy created engineer regiments. These were specialists in the creation of forts, bridges, entrenchments etc. They were organized like regular infantry regiments and trained in combat, but they usually didn't take part in combat. This does not mean it wasn't hazardous duty. Instead of fighting, they would work to create fortifications or bridges under fire. Union engineers put together pontoon bridges while being fired on by Confederate sharpshooters at Fredericksburg in December, 1862.

Cavalry Structures

(Refer to Infantry Structures, above)

Cavalry Troop or Company

Full Strength: 100 men

The cavalry company, or troop, was organized much along the same lines as an infantry company. The "ideal" size of a troop was 100 men. In actuality, there could be more men in a troop but it was quite often far less. When a cavalry unit fought dismounted, 1 man in 4 would stay behind and hold onto the horses while the other soldiers fought on the battle line.

See the Infantry Company listing, above, for more details.

Cavalry Battalion and Regiment

Full Strength: 1,000 to 1,200 men
Typical Strength: 300 to 600 men

In the Union, volunteer cavalry regiments consisted of 12 cavalry troops commanded by a colonel. In the Confederacy, 10 troops made up a cavalry regiment. In the Union regular army, the structure was different from either of these: 2 troops made up a squadron, 2 squadrons formed a battalion, and 3 battalions formed a regiment (for a total of 12 troops to the regiment).

If there were 4 to 8 troops of cavalry in a unit it was designated a battalion, not a regiment.

See the Infantry Battalion and Regiment listing, above, for more details.

Cavalry Brigade, Division and Corps

At the beginning of the war, individual Union cavalry regiments were assigned to infantry divisions, where they were often poorly used as pickets and messengers. The Confederates took their cavalry regiments and formed them into cavalry brigades, with these brigades often operating autonomously. Later on, the Union adopted this same type of organization.

A bit later in the war, the South formed cavalry divisions out of their cavalry brigades. Once again, the Union followed the Confederacy's lead. The Union was the first side to form cavalry corps, and this structure was copied by the Confederates.

Just like infantry, cavalry often had artillery batteries attached to them. This was horse artillery, which tended towards smaller guns of lighter caliber that keep up with the faster moving cavalry.

See the listings for Infantry Brigades, Divisions, Corps, and Armies, above, for more details.

Artillery Structures

Gun Detachment

Full Strength: 20 men and 1 cannon

The gun detachment consisted of a single cannon, its limber, 9 to 13 horses, 1 sergeant (chief of the piece), 2 corporals (gunner, and chief of the caissons), 6 to 10 cannoneers (privates operating the cannon), and 4 to 8 privates handling the horses and caissons. The top end gun crew size was 20 men.

Once a gun detachment started to take casualties, the numbers above would quickly drop. A gun could be fired — slowly — by a single gunner.

Artillery Section

Full Strength: 42 men and 2 cannons

Gun detachments were organized into sections. Each section consisted of two cannon crews, with a lieutenant in charge of each section.

Artillery Company or Battery

Full Strength: 80 to 150 men, and 4 to 6 cannons

The artillery unit roughly equivalent to an infantry company in size was the battery. Technically, the proper name for this level of organization in the U.S. army was "company". The term "battery" was not officially adopted by the War Department until July, 1866. During the Civil War, the word "battery" (from the French verb a battre, meaning "to beat or batter") was commonly used. When using company designations, they were lettered A through M (J was skipped as it was too easy to be confused with I).

In 1861, a typical Federal army battery consisted of 4 guns and 2 howitzers (see Common Artillery Terms, below, for the difference between guns and howitzers). As an example, a 6-pdr battery would have four 6-pdr smoothbore guns and two 12-pdr howitzers, while a 12-pdr battery would have four 12-pdr smoothbore guns and two 24-pdr howitzers. After the war began there was a tendency toward grouping weapons of like caliber in one battery. For most of the war a battery consisted of, typically, 4 cannons in a Confederate battery and 6 cannons in a Union battery. In May, 1864, Ulysses Grant had Union batteries reduced to 4 guns due to a shortage of horses.

The size of the battery was not a hard and fast rule. Cannons could be damaged or destroyed during combat. A battery might find itself reduced in size because of this, at least until the destroyed cannons could be replaced. Even after Grant ordered Union batteries to be reduced to 4 cannons, there were still batteries of 6 cannons. During the Atlanta campaign, the Union army had 29 four-cannon batteries, 22 six-cannon batteries, and 1 five-cannon battery.

A battery was commanded by a captain. Directly under him were 2 sergeants (orderly sergeant and quartermaster sergeant). Along with the cannons in the battery, there were also attached wagons and teamsters, artificers for keeping the wagons and cannons operational, and extra privates to take over in case of casualties.

Batteries were often grouped together into artillery regiments (see Artillery Regiments, below). These batteries were identified as part of a regiment, such as "5th Company, Washington Artillery", or "Company I, 1st U.S. Artillery". Some volunteer batteries were raised as units in their own right. In these cases the battery was named after the state where it was raised, just like an infantry regiment. An example of this is the 1st Minnesota Battery.

To make things confusing, a battery could also be identified with the officer in charge of the battery, so you have "1st Company, Richmond Howitzers" also known as "McCarthy's Battery". This gets even more confusing when the original officer in charge of the battery was killed or wounded and another officer took over. "Latimer's Battery" of the Courtney Artillery regiment might also be called "Tanner's Battery" after Capt. W. A. Tanner, who took over from Latimer. This web site uses all three designations when identifying artillery batteries, though the Orders of Battle give the official designation and the name of the officer in charge.

Even when a battery belonged to an artillery regiment, each battery acted separately and independently of the others in the regiment. The battery was still the most important artillery organization. Batteries from one regiment were often spread out within an army, or might serve with different armies in different theaters of the war.

Occasionally two batteries were consolidated, such as companies H & I of the 1st U.S. Artillery Regiment. This can be confusing to historians as they often mistake this combined unit for two separate units. The consolidation of batteries was usually a temporary measure, but at least one consolidation — companies B & L of the 2nd U.S. Artillery — occurred in 1861 and lasted the entire war.

Artillery Battalion and Brigade

Typical Strength: 3 or 4 batteries

At the beginning of the war each infantry brigade was assigned an artillery battery. The army also had an attached artillery reserve. By mid 1862, both the North and the South combined their artillery into larger units consisting of 3 to 4 batteries. In the North this unit was called a brigade and in the South it was called a battalion. A brigade or battalion was commanded by a colonel, a lieutenant colonel, or a major.

For a good portion of the war, artillery directly supported infantry brigades and divisions. Individual cannons, sections, or batteries were sometimes under the direct authority of a regimental commander. Artillery was, thus, a regimental or brigade support weapon. As such it was very difficult to coordinate large numbers of cannons during a battle, unless the artillery was part of the artillery reserve.

With the formation of artillery brigades, artillery could more easily fall under a division, corps, or army commander's control. By mid 1862, each division was typically assigned an artillery battalion/brigade, though these cannons were still mostly used for direct support of infantry brigades and infantry regiments.

Note that a Union artillery brigade was smaller than a Union artillery regiment. This is counter-intuitive as an infantry brigade is bigger than an infantry regiment. See Artillery Regiments, below.

Artillery Reserve

After the middle of 1862 each corps or army had an artillery reserve consisting of 2 to 5 battalions/brigades. The artillery reserve was used to form massed batteries. Instead of supporting individual regiments or brigades, the artillery reserve could be used to support the corps or army in general. An excellent example of this is the Union's use of its artillery reserve at Gettysburg in 1863, where artillery was massed against Pickett's Charge.

A colonel or brigadier general was usually in command of an artillery reserve.

Artillery Regiment

Full Strength: 1,000 to 1,800 men, up to 72 cannons

Some larger artillery organizations existed. These were artillery regiments, consisting of 10 to 12 batteries. From 1821 to 1861, the United States Army had four artillery regiments, consisting of 12 companies each. A fifth regiment, naturally called the 5th U.S. Artillery Regiment, was hastily formed on May 4, 1861 (and confirmed by Congress on July 29, 1861). Strangely enough, the "companies" in the 5th U.S. Artillery were formally called "batteries", a term that wouldn't be official in the rest of the U.S. army until 1866 (see Batteries, above).

The Union created some 32 heavy artillery regiments that were trained to fight as both infantry and artillery. They were originally intended for the defense of Washington, D.C. but Ulysses Grant added most of them to the Army of the Potomac in 1864 as very big infantry units. See the section on Infantry Regiments, above. These heavy artillery regiments contained 1,800 men, divided into 12 companies (batteries) of 150 men. The 12 companies were divided into three battalions of four companies, with each battalion under the command of a major. These heavy artillery regiment companies were organized very much like infantry companies, except that they had an extra captain, four extra lieutenants, and an additional 45 men. The extra men were needed to run the regiment's guns, resulting in companies one and half times the size of a regular full strength infantry company when they fought with muskets. During Grant's Overland campaign, these regiments were so big that they were often mistaken for infantry brigades.

Note: It is confusing but an artillery regiment was larger than an artillery brigade, while an infantry regiment was smaller than an infantry brigade.

Common Artillery Terms

This section includes some common artillery terms, which can help sort out some confusion with regard to artillery units.

2.9-inch, 3-inch, etc.: The barrel of a rifled cannon was rated to indicate what size of ammunition it fired. The inside of the barrel (known as the bore) was measured in inches. A 2.9-inch gun used ammunition that could fit a cannon with a barrel 2.9 inches in diameter. The most common field artillery pieces rated this way were the Model 1861 2.9-inch Parrott Rifle, the Model 1863 3-inch Parrott Rifle, and the Model 1861 3-inch Ordnance Rifle.

6-pdr, 12-pdr, 24-pdr, etc.: The term "pounder" (shortened to "pdr") is the size of a cannon's projectile. When cannons only fired solid shot, this indicated the weight of the cannon ball. This became irrelevant when shells were introduced in the 18th Century (shells weighed less than solid shot), but the old terminology continued to be used throughout the American Civil War. The most common field artillery pieces rated this way were the Model 1841 6-pdr smoothbore gun, the Model 1841 12-pdr smoothbore gun, the Model 1841 12-pdr smoothbore howitzer, the Model 1841 24-pdr smoothbore howitzer, and the Model 1857 Light 12-pdr smoothbore gun-howitzer (also known as the 12-pdr "Napoleon").

Canister: Canister was a type of close-range ammunition. It was essentially a big shot gun shell packed with musket balls. When fired, the balls would launch out with deadly effect. Canister was only effective on targets 300 yards away or less. When the enemy got very close, the artillery crew would sometimes fire "double canister", which consisted of putting one explosive charge in the gun followed by two canister rounds. Canister rounds were often aimed at the ground, when the earth was hard packed, so that the balls would ricochet off the ground and into a formation of troops from below, hitting more of them.

Case-Shot: Case-shot, or spherical case-shot, was a type of explosive projectile. Case-shot looked like a regular shell but the walls of the projectile were thinner. The inside of the projectile was packed with lead or iron balls. The case-shot would explode over troops, hitting them with these balls and case splinters. The effect was similar to that of canister, but over a longer range; while canister could only hit targets up to 300 yards away, case-shot was fired at targets no closer than 500 yards away.

Chambered Bore: A cannon barrel consisted of a big metal tube closed at one end. The end is known as the breech. The drilled out part of the tube is known as the bore. A gun had a chambered bore if the bore down at the breech was narrower than the rest of the bore. This created a cylindrical "chamber" that could hold the projectile's charge. Howitzers had chambered bores, but guns did not.

Field Artillery: This is the official term for artillery that served "in the field" with infantry and cavalry. They primarily used the Model 1841 6-pdr smoothbore cannon, the Model 1841 12-pdr smoothbore cannon, Model 1857 light 12-pdr gun-howitzer (also known as the 12-pdr "Napoleon"), the 10-pdr Parrot Rifle, and the 3-inch Ordnance Rifle. Mounted artillery served with infantry, while horse artillery served with cavalry.

Flying Artillery: This was another name for horse artillery made popular during the Mexican War.

Foot Artillery: This was another name given to heavy artillery. It was also used colloquially for artillerymen serving as infantry.

Gun: Technically, a gun was a type of artillery piece with a longer barrel than a howitzer, and which fired its shot in a flatter trajectory. Because they had a shorter barrel, they were heavier than howitzers. Guns were primarily designed to fire solid shot while howitzers fired shells. A gun used smaller charges than a howitzer. A gun did not have a chambered bore. "Gun" is a confusing term because it is often used as a generic term for an artillery piece. A reference may say a battery had "six guns", when in reality it had four guns and two howitzers. See also gun-howitzer.

Gun-Howitzer: A gun-howitzer was a hybrid cross between a gun and a howitzer. It had a longer barrel than a howitzer, but weighed less than the equivalent gun. It could fire shot and shell equally well, and in fact it only had "howitzer" attached to its name because it could fire shells. It lacked a howitzer's chambered bore. The famous gun-howitzer of the American Civil War was the Model 1857 12-pdr Napoleon. (The gun got its name from Emperor Napoleon III of France, who commissioned the weapon.)

Heavy Artillery: The heavy artillery referred to artillery that was too heavy to move. Actually, that's a bit misleading as they had to be moved to be put into position in the first place. However they were usually too large to be placed on a carriage and moved about with a regular army. They were used in coastal defenses, river fortifications, and semi-permanent defensive positions, such as the forts around Washington and Petersburg. Some "heavy artillery" pieces could move with an army. These were "siege guns", like the 30-pdr Parrott Rifle. They were moved on "siege carriages".

Horse Artillery: Horse artillery consisted of batteries that accompanied cavalry, acting as artillery support for mounted troops. Organizationally, they differed from field artillery batteries only in that each artilleryman rode his own horse. Usually horse artillery tended toward lighter guns of smaller caliber.

Howitzer: A howitzer was a cannon with a shorter barrel than a gun and with a chambered bore. Because of the shorter barrel, a howitzer was lighter than an equivalent gun. A howitzer was designed to lob shells so that they exploded above troops, or behind fortification walls. Howitzers used a smaller propelling charge than a gun. By contrast, guns were designed to fire solid shot. See also gun-howitzer.

Light Artillery: This was another name for horse artillery, though it is also sometimes used to mean field artillery. Although some artillery batteries had the word "light" in their name, they were not "light artillery" unless they were assigned to operate with cavalry.

Mounted Artillery: This is the official name for field artillery that served with infantry. It is not to be confused with horse artillery, which served with cavalry. This term dates back to before 1838 when the men who drove the horses in a U.S. artillery team actually rode horses and sometimes acted as cavalry, while the rest of the artillery team marched on foot and sometimes acted as infantry. After 1838 the division between the two types of artillerymen was eliminated. All the men in a team were cross trained and they took turns riding, thus they were all "mounted" at one time or another. This artillery branch kept the term "Mounted" to separate them from foot artillery. Mounted artillery was sometimes called "harnessed artillery".

Rifled Cannon: Rifled cannons were artillery pieces that had grooves, or "rifles", cut into the inside of the cannon's barrel in a spiral pattern. When the cannon fired, the projectile would expand so that it would catch in the grooves. As the projectile was forced up the barrel, it would start to spin. Oblong projectiles that spin around their long axis are much more accurate than spherical projectiles fired from smoothbore cannons, and they can reach greater distances. Because of the wear on the barrel and the pressure that could build up, rifled cannons were usually made of iron. The iron and their design made them heavier than bronze smoothbores. Rifles were not as good at firing canister rounds. Some of the balls in a canister round would catch in the grooves and spiral off in different directions when they left the barrel. This made canister less effective in rifled cannons.

Shell: Shells were a type of explosive projectile. They were essentially iron spheres containing explosives. They were designed to explode above troops, or bounce into troops and then explode, fall behind fortifications and explode, or slam into earthworks and explode. Fuses during the American Civil War were not very accurate, and shells often exploded prematurely or late, reducing their effect. The splinters of metal did not cause as much damage to troops as did the metal balls in case-shot, so case-shot was preferred against infantry.

Smoothbore: Most cannons in the American Civil War were smoothbores. This meant that the inside walls of the cannon's tube were smooth. Smoothbore cannons were less accurate than rifled cannons and had a shorter range. This wasn't much of a disadvantage during the war as cannons could only fire accurately at targets within line-of-sight, which was usually within smoothbore range. Smoothbores had the advantage that they were better at firing canister rounds, which caused Ulysses Grant to replace some rifled guns with smoothbores during his Overland Campaign. Smoothbores were usually made of bronze, thus they were lighter than rifled guns (which were made of iron).

Solid Shot: Solid shot was a type of artillery projectile. In smoothbore cannons it was the stereotypical cannon ball. In rifled cannons, it was an oblong projectile sometimes called a bolt. Solid shot was used to punch into large formations of troops, often bouncing across the battlefield until it ran out of momentum, or it was used to slam into fortifications or warships.


Attack and Die by Grady McWhitney and Perry D. Jamieson. Copyright 1982, published by The University of Alabama Press.

Battle In The Civil War by Paddy Griffith. Copyright 1986, published by Field Books.

Battle Tactics of the Civil War by Paddy Griffith. Copyright 1987, published by Yale University Press.

The Bloody Crucible of Courage: Fighting Methods and Combat Experience of the Civil War by Brent Nosworthy. Copyright 2003, published by Carroll and Graf. Glossary. A web site dedicated to Civil War artillery. This link takes you to their glossary section. The home page is found at

Civil War Weapons web site. A very useful web page covering Civil War artillery and small arms. The artillery articles were written by Jim Morgan.

Confederate Artilleryman: 1861-65 by Philip Katcher. Copyright 2001, published by Osprey Publishing Ltd. Part of its Warrior series (this is Warrior #34).

Infantry, Part I: The Regular Army by John K. Mahon and Romana Danysh. Part of the Army Lineage Series, published in 1972 by the Office of the Chief of Military History, United States Army. It can be found at

Regimental Losses of the Civil War by William F. Fox, Lt. Col., U.S.V. Copyright 1889. Originally published by Albany Publishing Company. Found on The Civil War CD-ROM, produced by Guild Press of Indiana, copyright 1997.

Unit Organization of the Civil War by Richard J. Zimmermann. Copyright 1982, published by RAFM Co. Inc.