Editing Union army (section)

==Organization==
[[File:GeorgeMcClellan1861a.jpg|thumb|General [[George B. McClellan]] with staff and dignitaries, including from left to right: Gen. George W. Morell, Lt. Col. A.V. Colburn, Gen. McClellan, Lt. Col. N.B. Sweitzer, [[François d'Orléans, Prince of Joinville|Prince de Joinville]] (son of King [[Louis Philippe I|Louis Philippe of France]]), and the prince's nephew, [[Prince Philippe, Count of Paris|Count de Paris]] (on far right)]]
===Leadership===
[[President of the United States|U.S. President]] [[Abraham Lincoln]] exercised supreme [[command and control]] over the army in his capacity as [[Powers of the president of the United States#Commander-in-chief|commander-in-chief]] of the [[United States Armed Forces]]. Below him was the [[Secretary of War]], who oversaw the administration of the army, and the [[General-in-chief#United States|general-in-chief]], who directed the field operations of the army.  

At the start of the war, [[Simon Cameron]] served as Secretary of War before being replaced in January 1862 by [[Edwin Stanton]].  The role of general-in-chief was filled by several men during the course of the war:<ref name=USAL195>United States Army Logistics, 1775–1992: An Anthology. (1997). United States: Center of Military History, U.S. Army. p. 194-195</ref>
*[[Winfield Scott]]: July 5, 1841{{spaced ndash}}November 1, 1861
*[[George B. McClellan]]: November 1, 1861{{spaced ndash}}March 11, 1862
*[[Henry W. Halleck]]: July 23, 1862{{spaced ndash}}March 9, 1864
*[[Ulysses S. Grant]]: March 9, 1864{{spaced ndash}}March 4, 1869

The gap from March 11 to July 23, 1862, was filled with direct control of the army by President Lincoln and Secretary Stanton, with the help of an unofficial "War Board" that was established on March 17, 1862. The board consisted of [[Ethan A. Hitchcock (general)|Ethan A. Hitchcock]], the chairman, with Department of War bureau chiefs [[Lorenzo Thomas]] (Adjutant General), [[Montgomery C. Meigs (1816–1892)|Montgomery C. Meigs]] (Quartermaster General), [[Joseph G. Totten]] (Chief of Engineers), [[James Wolfe Ripley|James W. Ripley]] (Chief of Ordnance), and [[Joseph P. Taylor]] (Commissary General).<ref>Eicher, pp. 37–38.</ref>

Reporting directly to the Secretary of War were the bureau chiefs or heads of staff departments which made up the [[Department of War]].  These included, at the onset of the war, the [[United States Army Adjutant General's Corps|adjutant general]], [[Office of the Inspector General of the United States Army|inspector general]], [[Paymaster-General of the United States Army|paymaster-general]], [[Judge Advocate General's Corps, United States Army|judge advocate general]], [[chief of engineers]], [[United States Army Corps of Topographical Engineers|chief of topographical engineers]], [[Quartermaster General of the United States Army|quartermaster general]], commissary general of subsistence, [[Chief of Ordnance of the United States Army|chief of ordnance]], and [[Surgeon General of the United States Army|surgeon general]].

After the war started, the position of [[United States Army Provost Marshal General|Provost Marshal General]] was also created.<ref name=USAL195/>  Originally established on September 24, 1862, as an office in the Adjutant General's department under [[Simeon Draper]], it was made an independent department in its own right on May 1, 1863, under [[James B. Fry]].<ref name="Eicher58">Eicher, p. 58</ref>  The [[Signal Corps (United States Army)|Signal Corps]] was created and deployed for the first time, through the leadership of [[Albert J. Myer]].

One drawback to this system was that the authority and responsibilities of the Secretary of War, his [[United States Assistant Secretary of War|Assistant Secretaries]], and the General-in-Chief were not clearly delineated.  Additionally, the efforts of the four "supply" departments (Quartermaster, Subsistence, Ordnance & Medical) were not coordinated with each other, a condition that would last throughout the war.  Although the "War Board" could provide military advice and help coordinate military policy, it was not until the appointment of Ulysses Grant as General-in-Chief was there more than the vaguest coordination of military strategy and logistics.<ref name=USAL195/>

===Major organizations===
The Union army was composed of numerous organizations, which were generally organized geographically.

; [[Union Army Divisions, Departments and Districts|Military division]]
: A collection of Departments reporting to one commander (e.g., [[Military Division of the Mississippi]], [[Middle Military Division]], [[Military Division of the James]]). Military Divisions were similar to the more modern term [[Theater (warfare)|Theater]]; and were modeled close to, though not synonymous with, the existing theaters of war.
; [[Union Army Divisions, Departments and Districts|Department]]
: An organization that covered a defined region, including responsibilities for the Federal installations therein and for the field armies within their borders. Those named for states usually referred to Southern states that had been occupied. It was more common to name departments for rivers (such as [[Department of the Tennessee]], [[Department of the Cumberland]]) or regions ([[Department of the Pacific]], [[Department of New England]], [[Department of the East]], [[Department of the West]], [[Middle Department]]).
; [[Union Army Divisions, Departments and Districts|District]]
: A territorial subdivision of a Department (e.g., District of Cairo, District of East Tennessee). There were also Subdistricts for smaller regions.
; Army
: The fighting force that was usually, but not always, assigned to a District or Department but could operate over wider areas.  An army could contain between one and eight corps, with an average of three.<ref name="Eicher66">Eicher, p. 65-66</ref>  Some of the most prominent armies were:
:*[[Army of the Cumberland]], the army operating primarily in [[Tennessee]], and later [[Georgia (U.S. state)|Georgia]], commanded by [[William S. Rosecrans]] and [[George Henry Thomas]].
:*[[Army of Georgia]], operated in the March to the Sea and the Carolinas commanded by [[Henry W. Slocum]].
:*[[Army of the Gulf]], the army operating in the region bordering the [[Gulf of Mexico]], commanded by [[Benjamin Butler (politician)|Benjamin Butler]], [[Nathaniel P. Banks]], and [[Edward Canby]].
:*[[Army of the James]], the army operating on the [[Virginia Peninsula]], 1864–65, commanded by Benjamin Butler and [[Edward Ord]].
:*[[Army of the Mississippi]], a briefly existing army operating on the Mississippi River, in two incarnations—under [[John Pope (general)|John Pope]] and [[William S. Rosecrans]] in 1862; under [[John A. McClernand]] in 1863.
:*[[Army of the Ohio]], the army operating primarily in [[Kentucky]] and later Tennessee and Georgia, commanded by [[Don Carlos Buell]], [[Ambrose E. Burnside]], [[John G. Foster]], and [[John M. Schofield]].
:*[[Army of the Potomac]], the principal army in the [[Eastern Theater of the American Civil War|Eastern Theater]], commanded by [[George B. McClellan]], Ambrose E. Burnside, [[Joseph Hooker]], and [[George G. Meade]].
:*[[Army of the Shenandoah (Union)|Army of the Shenandoah]], the army operating in the [[Shenandoah Valley]], under [[David Hunter]], [[Philip Sheridan]], and [[Horatio G. Wright]].
:*[[Army of the Tennessee]], the most famous army in the [[Western Theater of the American Civil War|Western Theater]], operating through Kentucky, Tennessee, Mississippi, Georgia, and the [[Carolinas]]; commanded by [[Ulysses S. Grant]], [[William T. Sherman]], [[James B. McPherson]], and [[Oliver O. Howard]].
:*[[Army of Virginia]], the army assembled under [[John Pope (general)|John Pope]] for the [[Northern Virginia Campaign]].

Each of these armies was usually commanded by a [[Major general (United States)|major general]]. Typically, the Department or District commander also had field command of the army of the same name, but some conflicts within the ranks occurred when this was not true, particularly when an army crossed a geographic boundary.

The commanding officer of an army was authorized a number of [[aides-de-camp]] as their personal staff and a general [[Staff (military)|staff]].  The general staff included representatives of the other combat arms, such as a chief of artillery and chief of cavalry (the infantry being typically represented by the commanding officer) and representatives of the staff bureaus and offices.<ref name="Eicher40">Eicher, p. 40</ref>  The staff department officers typically assigned to an army or military department included an assistant adjutant general, a chief quartermaster, a chief commissary of subsistence, an assistant inspector general, an ordnance officer (all with the rank of [[colonel]]) and a medical director.<ref name="newell71">newell & shrader, p. 71</ref>  The actual number of personnel assigned to an army's headquarters could be quite large: at Gettysburg the headquarters of General Meade (excluding engineers, the artillery reserve and the headquarters of each corps) was no less than 3,486 strong.<ref>Griffith, P. (2001). Battle Tactics of the Civil War. United Kingdom: Yale University Press. p. 55</ref>

===Tactical organizations===
The [[military organization]] of the United States Army was based on the traditions developed in Europe, with the [[regiment]] being the basis of recruitment, training and maneuvering. However, for a variety of reasons there could be vast differences in the number of actual soldiers organized even into units of the same type. Changes in how units were structured during the course of the war, contrasts in organizational principals between regular and volunteer units, and even simple misnaming all played a role. Thus for example, comparing two infantry regiments at their full authorized strength one might have twice as many soldiers as the other. Furthermore, even when units were of equivalent size, their actual effectiveness depended greatly on training, leadership, equipment and other factors.<ref name="Eicher66" />
{|class="wikitable" style="display: inline-table;" 
! style="text-align:center; background:#acc;" |Name
! style="text-align:l center; background:#acc;" |Commander
! style="text-align:l center; background:#acc;" |Sub-units
! style="text-align:center; background:#acc;" |Soldiers
! style="text-align:center; background:#acc;" |Notes
|-
|+Union army tactical organizations<ref name="Eicher66"/><ref name="NCMuseum">{{cite web|title=Civil War Army Organization and Rank|url=https://www.ncmuseumofhistory.org/civil-war-army-organization-and-rank|publisher=North Carolina Museum of History|access-date=6 August 2021|archive-date=July 18, 2017|archive-url=https://web.archive.org/web/20170718010330/http://ncmuseumofhistory.org/civil-war-army-organization-and-rank|url-status=dead}}</ref><ref name="McGrath">McGrath, p. 17–20</ref><ref name="Wilson">Wilson, p. 12–15</ref>
|-
|[[Corps#American Civil War|Corps]]
|Major general
|2–6 divisions
|36,000
|Averaged three divisions, included a dedicated artillery brigade after 1863. See also [[Cavalry Corps (Union Army)|Cavalry Corps]].
|-
|[[Divisions of the United States Army#American Civil War|Division]]
|Major general
|2–6 brigades
|12,000
|Averaged three brigades for infantry divisions, two brigades for cavalry. Also included attached [[artillery battery|artillery batteries]] until 1863.
|-
|[[Brigade (United States Army)|Brigade]]
|[[Brigadier general (United States)|Brigadier general]]
|2–12 regiments
|4,000
|Averaged four regiments for both infantry and cavalry.  Artillery brigades consisted of between four and six batteries.
|-
|[[Regiment (United States Army)|Regiment]]
|[[Colonel (United States)|Colonel]]
|10 companies
|1,000
|Actual size would vary as attrition reduced the regiment down to several hundred soldiers or fewer. Artillery regiments consisted of twelve batteries but were purely administrative units.
|-
|[[Battalion (United States Army)|Battalion]]
|[[Major (United States)|Major]]
|Varied
|Varied
|With some exceptions, a battalion may refer to any two or more companies of a regiment or if a regiment consisted of between four and eight companies total.
|-
|[[Company (United States Army)|Company]]
|[[Captain (United States O-3)|Captain]]
|2 platoons
|100
|Cavalry equivalent referred to as a [[troop]]. Artillery equivalent referred to as [[artillery battery|battery]], contain between four and six artillery pieces.
|}

{{Union Army Formations}}