Organization of the Armies in the Civil War

           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." Actually, it would appear that the armies took their names from the departments in which they operated (or were originally formed), and these departments took their names from rivers in the case of the Federals and from states or regions in the case of the Confederates. 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 were at least 16 on the Union side and 23 on the Confederate side.

        CORPS: The term corps comes from the French corps d'armee.  Although corps d'armee existed in the French army before Napoleon, he revamped them and popularized the phrase.   A corps was composed of 2 or more divisions and, except for Cavalry corps, included all arms of service.
        Corps were established in the Union army in March 1862 by Maj. Gen. George B. McClellan.  A major general commanded each of the 43 corps that were established in the Union army before the end of the war.  Each corps was designated by a number, I to XXV.  Corps badges such as triangles, crescents, arrows, and acorns were adopted by most corps and worn by officers and enlisted men.  Of the Union corps 2 were noted for their failures:  the XI Corps, which took flight after a surprise attack by Lt. Gen. Thomas J. "Stonewall" Jackson's men at Chancellorsville and the IX Corps, which bungled the opportunity of the Crater at Petersburg.  More successful corps included the I and II/ Army of the Potomac, known for their bravery; the XXV, composed entirely of black troops and the XXII corps, which garrisoned the fortifications around Washington, D.C. during most of the war and guarded the Union capital.
        Corps were organized in the Confederate army November, 1862 and were designated by numbers duplicated in the East and West but were often referred to by the name of their commander.  Thus, the II Corps in the East was called Jackson's Corps, even after he was killed.  This corps endured some of the hardest marching and heaviest fighting of the war.
        After their initial trial in the Civil War, corps became an integral part of the organization of the U.S. Army in wartime. 

        DIVISIONS: In field armies on both sides in the Civil War, the division was the second largest unit.  In ascending order of size, units were: company, regiment brigade, division, corps.   Theoretically, company strength was 100; regiment, 1,000; brigade, 4,000; and division, 12,000.  Occasionally, more often in the Confederate army battalions of 2 to 10 companies were accepted into the ranks.  In the Union army, the actual numbers, by the attrition of war, were only 40-50% of those figures by 1863; the percentage was higher in the Confederate army, thanks to its system of assigning recruits to existing regiments instead of creating new regiments.
        In the Union armies the number of division in a corps varied from 2 to 4, though usually there were 3.  In spring 1863, Maj. Gen. Joseph "Fighting Joe" Hooker ordered the army of the Potomac to wear Corps Badges, which led to designating divisions by badges and by flags in red, white, and blue, for 1st, 2nd, and 3rd, divisions, respectively;  the few 4th divisions had green badges and flags; 5th divisions, orange.  Without uniform badges and flags, the Confederates used a less complicated system.  Though they began by numbering their divisions, in a short time divisions, as well as other army units, come to be known by their commanders' name.
        Union division were commanded by brigadier or major generals, and the frontage of an average 1863 Union division, drawn up in double-rank line of battle with no skirmishers deployed, would have been just short of a mile.  The Confederates were more logical:  with rare exceptions, brigadiers commanded brigades and major generals led division, and these units were usually numerically superior to their Union counterparts.  An extreme example:  at one time Confederate Maj. Gen. Ambrose P. Hill's famous Light Division had 7 brigades, giving it a strength of about 17,000. 

        BRIGADES:  The tactical infantry unit of the Civil War, the brigade generally consisted of 4-6 regiments.   However, it could have as few as 2 and later in the war, when consolidation of Confederate regiments became common, some brigades contained remnants of as many as 15 regiments.  There were 3 or 4 brigades to a division and several divisions to a Corps.  By definition, a brigadier general commanded a brigade.  But colonels were often in charge of brigades too small to justify a brigadier, and if the brigadier was absent, the senior colonel would act in his stead; on occasion, temporary brigades organized for special purposes were commanded by colonels.  The brigade's staff usually comprised the brigadier general, his aide, the quartermaster, ordnance and commissary officers, and inspector, and one or more clerks.
        The brigade's effectiveness depended on regimental and company commanders instructing their 1,000-1,500 men in the complicated maneuvers of the period, and on each regiment coordinating its movements with the others under the brigade commander commander.  A poor commander might watch his brigade's actions dissolve into regimental or company-level conflicts coordinated loose, if at all, by the brigadier. 
        Confederate brigades were known by the names of their commanders or former commanders, a much less prosaic system than that of the Federals, but a very confusing one. For example. the unit of "Pickett's Charge" at Gettysburg shown in Steele's American Campaigns as "McGowan's Brigade" was commanded by Pettigrew until 1 July '62 and then by Marshall. In this attack Pettigrew is commanding "Heth's Division," Trimble is commanding "Pender's Division," Mayo is commanding "Brockenbrough's Brigade," Marshall is commanding "McGowan's" or "Pettigrew's Brigade," Fry is commanding "Archer's Brigade," and Lowrance is commanding "Scales's Brigade."
        Some of the brigades became justly famous during the war.  The Stonewall Brigade was one of Gen. R.E. Lee's best units, as was Hood's Texas Brigade.  Western Confederate brigades included the Orphan Brigade of Kentucky and the 1st Missouri Brigade.  On the Union side, the Iron Brigade earned fame in the Army of the Potomac, as did the Philadelphia Brigade.  Wilder's Lightning Brigade of mounted infantry combined infantry and cavalry tactics to become one of the best Union units.   

        INFANTRY REGIMENTS were composed of 10 companies, except in the case of the 12-company heavy artillery regiments that had been retrained as infantry. Cavalry regiments also had 12 companies. These companies were lettered in alphabetical order, with the letter "J" omitted. There has been much erroneous theorizing as to why the US Army has never had a J Company.   Battalions did not exist in the infantry regiments, but the "heavies" were composed of three four company battalions, each commanded by a major.
        Confederate regiments were organized in generally the same manner as the Federal, although some had battalions (e.g., the 55th Ala.) and the 7th Ala. had two cavalry companies initially.
        In the Union Army an infantry company had a maximum authorized strength of 101 officers and men, and a minimum strength of 83. The company was allowed to recruit a minimum of 64 or a maximum of 82 privates. Other company positions were fixed as follows: one captain, one first lieutenant, one second lieutenant, one first sergeant, four sergeants, eight corporals, two musicians, and one wagoner. Company officers were elected in most volunteer units.
        As Schiebert, the Prussian observer, points out, this was the only possible way of getting rapidly the large number of troop leaders needed. By the second year of the war a system of examinations was instituted by both armies, and incompetent officers could be eliminated (Schiebert, 39-40).
        Regimental headquarters consisted of a colonel, lieutenant colonel, major, adjutant, quartermaster, surgeon (major), two assistant surgeons, and a chaplain. Regimental headquarters 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. According to Fiebeger the average company strength at Gettysburg was 32 officers and men per company. Livermore gives these average regimental strengths in the Union army at various periods: Shiloh, 560; Fair Oaks, 650; Chancellorsville, 530; Gettysburg, 375; Chickamauga and the Wilderness, 440; and in Sherman's battles of May '64, 305. According to Bigelow the average strength of Federal regiments at Chancellorsville was 433 and of Confederate regiments 409.
        The North raised the equivalent of 2,047 regiments during the war of which 1,696 were infantry, 272 were cavalry, and 78 were artillery. Allowing for the fact that nine infantry regiments of the Regular Army had 24 instead of the normal 10 companies, the total number of regiments would come to about 2,050, not including the Veteran Reserve Corps. (Above figures from Phisterer, 23.) According to the computations of Fox, made before the Official Records had all been published, the South raised the equivalent of 764 regiments that served all or most of the war. Using later data, and including militia and other irregular organizations, Col. Henry Stone estimated an equivalent of 1,009 Confederate regiments. (For exhaustive study of Confederate strengths see Livermore.)
Source:  "Civil War Dictionary" By Mark M. Boatner III and "The Historical Times Encyclopedia of the Civil War" edited by Patricial L. Faust.

This Page last updated 02/10/02

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