If you are new to research, the organization and terminology used for Civil War armies can be very confusing. Terms such as corps, battalion, regiment, company, brigade, theater, and divisions have little reference to non-military people today.
This section explains the basic terms and structure.
The study of the war is divided into three major areas:
- Eastern Theater (Virginia)
- Western Theater (Everywhere else)
- Trans-Mississippi (West of the Mississippi River)
ARMIES were the largest of the "operational organizations." In the case of the Federal forces, these generally took their name from their department. "The Federals followed a general policy of naming their armies for the rivers near which they operated; the Confederates named theirs from the states or regions in which they were active. Thus the Federals had an Army of the Tennessee -not to be confused with the Confederate Army of Tennessee." There were no firm rules on this matter of names, however: there was a Confederate Army of the Potomac; and the Confederate Army of (the) Mississippi is referred to in the Official Records about as often with "the" as without. These armies numbered at least 16 on the Union side and 23 on the Confederate side.
By mid-war The "Army of the Potomac" was the main Union army in the eastern theater of the war and the "Army of Northern Virginia" was the main Confederate force. Early on they went by various names and both sides had an “Army of the Potomac” at one point. Both armies were organized in a similar fashion including a structure of corps, divisions, brigades, regiments and companies.
For Alabama research Union troops were “the Army of Tennessee” under General Oliver O. Howard and “The Army of Georgia” under General Henry W. Slocum. The Army of Tennessee consisted of the XV & XVII corps and The Army of Georgia consisted of part of the XIV Corps, The Army of the Cumberland, and the XX Corps. Both of these armies were under the overall command of Gen. William T. Sherman and numbered about 60,000 troops plus a Cavalry corps of 4,000 men under Gen. Hugh Judson Kilpatrick.
For Confederate troops the Army of Tennessee under the command of Gen. Joseph T. Johnson numbered about 20,000 plus another 10,000 militia, state troops, and home guard units from Georgia and South Carolina under Gen. Lafayette McLaws. The Federal government and the Confederate government both had war departments which oversaw the organization, supply, and movements of their respective armies. Civil War era armies were organized according to military manuals including those adopted by the Federal War Department prior to 1861. Because the war had to be fought over a large area of the South, the Union and the Confederacy both had several armies, each fighting in different "theaters" or sections of the country. Each army was a structured organization that included a general headquarters, infantry, artillery, cavalry, signalmen, engineers, quartermaster and commissary depart-ments.
The largest single organization of an army was a corps (pronounced "core"). The army consisted of two or more Corps or on rare occasions Wings - Corps are usually named for the commander - two of the most famous, Longstreet's Corps and Jackson's Corps, Army of Northern Virginia. A Corps normally consists of Divisions.
The Union Army at Gettysburg had seven infantry corps and a cavalry corps, each commanded by a major general. The Confederate Army had three infantry corps, each commanded by a lieutenant general. Typically, a Confederate corps was much larger than a Union corps. A corps included three infantry divisions and an artillery brigade in the Union army or an artillery battalion in the Confederate Army. The Army of the Potomac had distinguishing symbols called corps badges to signify one corps from another. The badges were actually small cloth cut-outs shaped like crosses, spheres, stars, and quarter moons, and made in three different colors- red, white, and blue, each color specific to a division of the corps. Confederates had no corps badges or particular symbols for their organizations.
Divisions - two or more Brigades - usually named for the commander - Wilcox's Division, Hill or Jackson's Corps, Army of Northern Virginia. A Division normally consists of two or more Brigades. The Division is normally commanded by a Major General.
Brigades - two or more regiments - usually named for the commander - McGowan's Brigade, Wilcox's Division, Jackson or Hill's Corps, Army of Northern Virginia - A Brigade normally consists of two or more regiments and battalions - Orr's First South Carolina Rifles, McGowan's Brigade, Wilcox's Division, Jackson or Hill's Corps, Army of Northern Virginia. A Brigade consisted of four to six regiments and is commanded by a Brigadier General. It was the primary organization used by commanders in battle. A brigade with good officers and good training was a formidable fighting force and often advanced or defended positions in cooperation with fellow brigades. It was common practice for a brigade commander to send forward most of his regiments and hold one in reserve. The Confederate War Department made attempts to have brigades composed of regiments from one singular state or state affiliation, such as General Joseph Kershaw's brigade composed of all South Carolina regiments. The Union Army did not always make such conscious choices, though there were some brigades which acquired interesting nick names due to their ethnic origin or locality from which they hailed. Regiments - normally consists of 10 companies, although other configurations were used especially early in the war - The Regiment was command by a Colonel. Company - Ideally made up of 100 men, although some had as many as 300 men early in the war and were down to 10 or 15 by the end. The company was commanded by a Captain.
Legions - were a popular unit early in the war and consisted of Infantry, Cavalry, and Artillery. Many were broken up early in the war. The only legion formed in Alabama was Hilliard’s Legion, but you will also found Alabama men in Floyd’s Legion and Smith’s Legion which were formed in Georgia and the Mississippi “Army of 10,000.” For the infantry, the regiment was the most important unit. Led by a colonel, Lieut. colonel and major, a full strength regiment numbered over 1,000 officers and men. A regiment was divided into ten companies of 100 men each at full strength. Each company was led by a captain with two lieutenants who each commanded a platoon. Platoons were divided into squads, led by a sergeant or corporal. These squads were generally referred to as a “mess.”
Regimental headquarters consisted of a colonel, lieutenant colonel, major, adjutant, quartermaster, surgeon (major), two assistant surgeons, and a chaplain. Noncommissioned officers were the sergeant major, quartermaster sergeant, commissary sergeant, hospital steward, and two principal musicians. Authorized strength of an infantry regiment was a maximum of 1,025 and a minimum of 845. Since it was the Civil War practice to organize recruits into new regiments rather than to send them to replace losses in veteran units, regimental strengths steadily declined.
Numbers were much more fluid in the Confederate Army. Often in Alabama you will find 3,000 or more men in the early regiments and only 300 to 400 in those formed later in the war. By the time of Sherman’s invasion, most Confederate units numbered barely a hundred men and many had already been consolidated several timed due to losses.
Attrition due to disease and battle losses meant considerably lower personnel in each regiment. Regiments fought in a "battle line" or in some cases a "skirmish line", which was a general open rank tactic used to feel out the strength of an enemy force.
War Departments in the North and South issued regulations for how the army was to be organized in the field though commanders were also given the luxury of making changes in the organization as they saw fit. Thus there were often variances from the chart seen here especially in the Army of the Potomac, which lost regiments due to the expiration of their term of service or consolidated organizations due to battle-related attrition. Though the Union army's corps were each designated to have three divisions, the Third Corps and Twelfth Corps only had two divisions apiece at Gettysburg. Likewise, the Eleventh Corps' organization varied from the regulations having only two brigades in each of its three divisions.
Army Organization Comparison Chart: ARMY OF THE POTOMAC ARMY OF NORTHERN VIRGINIA 1 Corps = 3 Divisions 1 Corps = 3 Divisions 1 Division = 3 Brigades 1 Division = 4 to 5 Brigades 1 Brigade = 4 to 5 Regiments 1 Brigade = 4 to 6 Regiments 1 Regiment = 10 Companies (1,100 officers and men) 1 Regiment = 10 Companies (1,100 officers and men) 1 Company = 2 to 3 Platoons* (100 officers and men) (* depending on military organization manual) 1 Company = 2 to 3 Platoons* (100 officers and men) (* depending on military organization manual) 1 Platoon = 5 Squads (1 officer & 50 men) 1 Platoon = 5 Squads (1 officer & 50 men)
At the outbreak of the Civil War, there was a standing force of "regular" units in the United States Army. State militias were called into service, but there was a need to Federalize these units so that they could muster pay from the United States government and serve outside of state borders. Each state was given a quota of "volunteer regiments" to be raised for service lasting from three months to three years. The South faced a similar dilemma. Southern states raised and supplied the Confederate armies with volunteer regiments. By 1863, many of the regiments in both armies had been in service since 1861 and were still composed of mostly volunteer soldiers, though the first "conscripts" or men required by state law to serve in the military defense of a state, had begun to appear in Southern units. A regiment's flag, or "regimental colors", were painted with the regiment's number and state affiliation, usually followed by "VOLUNTEER INFANTRY". The term volunteer was a symbol of pride for soldiers on both sides.
The artillery was usually organized by regiments as well, except that each company was called a battery. A battery consisted of over 100 soldiers, armed with six cannon per battery. Confederate batteries were smaller, some having only four cannon. Batteries were assigned independently from their regiments to specific artillery brigades (Union) or battalions (Confederate) or to the artillery reserve of an army. Both of the armies had an artillery reserve which was an organization of extra batteries to be placed where needed. The Union army had one large artillery reserve force. The Confederate army had one reserve group per corps, but the number of guns was still smaller than the number of Union cannon.
A cavalry regiment was organized in a similar fashion to the infantry and artillery. Ten to twelve companies or "troops", made up one regiment. The regiment was divided into three battalions, each composed of four companies. A company was divided into "squadrons" for easy maneuvering on the field.
Both armies also had a compliment of quartermaster, engineer, and signal units as well as supply wagons organized as "trains". An army on the march was usually followed by miles and miles of wagons loaded with the equipment of war including food, ammunition, and medical supplies. At the top of the organizational list was the Army Headquarters. The commanding general required a personal staff to dictate orders and keep records of army movement. There were also clerks and assistants. The commanders of armies also had the privilege of a headquarters cook. Every army headquarters usually had a large compliment of staff officers, couriers, and a headquarters guard, which included an infantry battalion and a cavalry escort.
Excerpted from "A Guide to Civil War Research" by John Rigdon [http://www.amazon.com/Guide-South-Carolina-Civil-Research/dp/1461007747/ref=sr_1_1?ie=UTF8&qid=1308446628&sr=8-1]