Editing Union army (section)

==Army administration and issues==
===Adjutant General's Department===
{{main|United States Army Adjutant General's Corps}}
[[File:Gen. Lewellyn F. Haskell - NARA - 528379 Restored.jpg|thumb|right|[[Llewellyn F. Haskell]] (1842–1929), [[United States Army]] officer and a Union [[General officer|general]] during the [[American Civil War]]]]

The responsibilities and functions of the Adjutant General's Department (AGD) were many and varied during the course of the Civil War, but principle among them was handling military correspondence between the President, Secretary of War and General-in-Chief, and the rest of the army. Other functions included administering recruitment, overseeing the appointment of [[chaplain]]s, maintaining personnel records, and issuing instruction books and other [[Form (document)|forms]]. During the war, some of the department's responsibilities and functions were spun off to new offices while new ones were added. The recruitment of new white volunteers and draftees, and the suppression and punishment of [[absenteeism]] and [[desertion]], was given to the newly formed Provost Marshal General's Bureau in May 1863, while the position of [[Commissioner for the Exchange of Prisoners]] was created to take over this function from the AGD. The [[Bureau of Colored Troops]] was created within the AGD specifically to oversee the creation of the [[United States Colored Troops]], and in the final year of the war the AGD was given the responsibility for collecting and editing documents which would constitute ''The War of the Rebellion: A Compilation of the Official Records of the Union and Confederate Armies''.<ref name="Newell90">Newell & Shrader, p. 85-90</ref>

At the start of the Civil War, the AGD numbered just fourteen regular officers: the [[United States Army Adjutant General's Corps|Adjutant General]] (AG) with the rank of colonel, a lieutenant-colonel, four brevet majors, and eight brevet captains. In August 1861 the AG was raised to major-general and the strength of the AGD increased to twenty officers, and a year later it was reorganized to constitute the AG, two colonels, four lieutenant-colonels, and thirteen majors. The small number of civilian clerical staff supporting the officers was also increased as the war progressed, including the addition of up to ten noncommissioned officers by 1862. However to meet the need for assistant adjutant generals authorized for each corps, division and brigade, appointments were made from among the volunteer forces, and by 1865 there were an additional 85 majors and 256 captains serving in these capacities. At the regimental level, one of the unit's lieutenants would be selected to serve as its adjutant.<ref name="Newell90"/>

In spite of the rapid increase of the army at the start presenting numerous challenges and being perpetually understaffed throughout the war, the AGD appears to have handled its responsibilities competently and with little disruption. The AGD also had fewer conflicts with field commanders compared to some of the other departments, partly because its authority was well-established and issued few controversial orders itself, and it was less affected by matters of procurement and emerging technologies.<ref name="Newell90"/>

;Leadership
Colonel [[Lorenzo Thomas]] was named Adjutant General of the army on March 7, 1861, one day after Col. [[Samuel Cooper (general)|Samuel Cooper]] resigned the join the Confederacy.  While Thomas served as the AG throughout the entirety of the war, he eventually ran afoul of Secretary Stanton, who reassigned him to the job of recruiting soldiers for black regiments in the [[Western Theater of the American Civil War|western theater]].  From March 1863 on then, the assistant adjutant general Colonel [[Edward D. Townsend]] essentially was the acting AG in Washington.<ref name="Newell90"/>

===Bureau of Military Justice===
{{main|Judge Advocate General's Corps, United States Army}}
An office of the [[Judge Advocate]] had existed in the US Army since its founding, consisting at the start of the Civil War of a single officer with the rank of major and small civilian clerical staff in Washington.  It was not until after the war began however that Congress formally authorized the appointment of a [[Judge Advocate General]] (JAG) and creation of the Bureau of Military Justice, a [[de facto]] department and forerunner to a true Judge Advocate General's Department.  The principle functions of the JAG included conducting [[Courts-martial of the United States|courts-martial]] and [[inquiry|inquiries]]; codifying the [[law of war|laws of war]] and the [[Uniform Code of Military Justice|military laws of the United States]]; reviewing the records of courts-martial, military commissions and inquiries; and asserting the jurisdiction of military commissions over civilians in times of war.<ref name="Newell98">Newell & Shrader, p. 94-98</ref>

To meet the demands of a vastly larger army, Congress authorized in July 1862 the appointment of a JAG with the rank of colonel and for President Lincoln to appoint a judge advocate of volunteers with the rank of major for each army in the field.  These judge advocates were to advise commanders on legal issues, prosecute offenses, and review and maintain the records of courts-martial and other proceedings in the field.  A year later, Congress legislated the creation of the Bureau of Military Justice, gave it an [[appellant]] function, and authorized the JAG to head it as a brigadier general alongside an assistant JAG with the rank of colonel.  With these authorizations came a small increase in the size of the clerical staff assisting the JAG.<ref name="Newell98"/>

During the war the JAG and his subordinates were able to satisfactorily handle the increased volume and complexity of legal matters that came with the exponential growth of the army.  Among their most important accomplishments was the creation of the [[Lieber Code]] and, for the first time, collecting all precedents, decisions and opinions which had become US military law into a single digest and publishing it in early 1865.  One of the most controversial issues associated with the bureau was the use of military commissions to try civilians, an issue which would not be settled until ''[[Ex parte Milligan]]'' was decided in 1866.<ref name="Newell98"/>

;Leadership
The Civil War began with brevet Major [[John F. Lee]] serving as the judge advocate of the army until September 3, 1862, when [[Joseph Holt]] was formally appointed as JAG.  Holt played an important parts in helping to expanding the office of the JAG and oversaw some of the most important and sensitive trials of the war.  However Holt also made many enemies while JAG and was severely criticized for his handling of the [[Assassination of Abraham Lincoln#Conspirators' trial and execution|trial of President Lincoln's assassins]].<ref name="Newell98"/>

===Bureau of Refugees, Freedmen, and Abandoned Lands===
{{main|Freedmen's Bureau}}
In March 1865 the Bureau of Refugees, Freedmen, and Abandoned Lands was created by Congress with a mandate to see to the needs of all Black freedmen and white refugees, and the management of all lands within the rebel states which had been abandoned or otherwise come into the possession of the United States.  It consisted of a commissioner as head of the bureau, an assistant commissioner for each of the rebel states, and a small staff of one chief and nine other clerks.  Additionally, any military officer could be assigned to duty on behalf of the bureau.  Major General [[Oliver Otis Howard]] was appointed to head the bureau at its creation and lead it throughout its lifetime.  While the Freedmen's Bureau was the center of much controversy during the [[Reconstruction era]] and some of the relief it provided was less than satisfactory, its most important contribution was in providing education to many Blacks and poor whites.<ref name="Newell107">Newell & Shrader, p. 106-107</ref>

===Corps of Engineers===
{{Main|United States Army Corps of Engineers}}
The Corps of Engineers was a small part of the army prior to the Civil War but played an important role not only in the conflict but for the nation as a whole.  The Corps was responsible for running the [[United States Military Academy]] at [[West Point, New York|West Point]], which supplied officers to all branches but whose top graduates were commissioned into the Corps. They were not only involved with [[military engineering]] such as constructing [[fortifications]] and harbor defenses but also oversaw [[civil engineering]] including building canals, bridges and similar projects. This focus on civil works did prevent the Corps from devoting its entire effort to the war though.<ref name="Newell292">Newell & Shrader, p. 285–292</ref><ref name="Baldwin18">Baldwin, W. (2008). ''The U.S. Army Corps of Engineers: A History''. United States: Headquarters, U.S. Army Corps of Engineers, Office of History. p. 15–18</ref> Corps personnel acted as [[combat engineer]]s during battle, helping to construct [[pontoon bridge]]s, repair roads and bridges, dig [[Trench warfare|trenches]], and conduct [[Engineer reconnaissance|reconnaissance]]. The Corps also exerted an influence beyond its small size as many of the Union's most prominent officers, including McClellan and Meade, were themselves trained as engineers and used their knowledge to influence the outcome of battles.<ref name="Newell292" /><ref name="Baldwin110">Baldwin, p. 107–110</ref>

Prior to the war, the Corps of Engineers consisted of just forty-eight officers and a single company of 150 engineer troops.  Engineer Company A was first created for the [[Mexican–American War]] and guarded President Lincoln at his [[First inauguration of Abraham Lincoln|first inauguration]].<ref name="Newell292" /><ref name="Baldwin110" /> It was organized with ten sergeants (master-workmen), ten corporals (overseers), two musicians, sixty-four first-class privates ([[Armed-forces artificer|artificers]]) and sixty-four second-class privates (laborers).<ref>Callan, J. F. (1864). The Military Laws of the United States, Relating to the Army, Volunteers, Militia, and to Bounty Lands and Pensions, from the Foundation of the Government to 4 July 1864: To which are Prefixed the Constitution of the United States (with an Index Thereto,) and a Synopsis of the Military Legislation of Congress During the Revolutionary War. United States: G.W. Childs. p. 24–25</ref> In August 1861 Congress authorized the formation of three more companies to be organized the same as Engineer Company A, with all four organized into a single battalion (the US Engineer Battalion, later [[1st Engineer Battalion (United States)|1st Engineer Battalion)]], and the addition of two lieutenant colonels, four majors and six lieutenants to the Corps. The battalion had no formal headquarters but fell under the command of the most senior officer present. In March 1863, when the Corps of Topographical Engineers was disbanded and its function merged with the Corps of Engineers, Congress further revised the Corps to consist of a brigadier-general as Chief Engineer, four colonels, ten lieutenant-colonels, twenty majors, thirty captains, thirty first lieutenants and ten second lieutenants.<ref name="Newell292" /><ref name="Baldwin110" />

The US Engineer Battalion served ably as part of the Army of the Potomac, but on its own was insufficient to see to the army's need for engineers throughout the different theaters of war. A small number of volunteer engineer regiments were formed during the war, including the [[1st Michigan Engineers and Mechanics Regiment]], the [[1st New York Engineer Regiment]] and the [[1st United States Veteran Volunteer Engineer Regiment]]. However, in many cases engineering work was carried out by line soldiers under the supervision of officers with engineering backgrounds, if any were available.<ref name="Newell292" /><ref name="Baldwin110" /> Most types of engineering work, such as digging simple [[Earthworks (military)|earthworks]] or laying small bridges, did not require the specialized skills of engineers, which were required for complex endeavors like constructing pontoon bridges or forts. Union armies typically detailed soldiers to form company-sized detachments of [[Pioneer (military)|pioneers]] to repair roads or bury the dead after a battle.<ref>Hess, E. J. (2005). ''Field Armies and Fortifications in the Civil War: The Eastern Campaigns, 1861–1864'' (Civil War America). United Kingdom: University of North Carolina Press. p. 15–16</ref>
;Leadership
*[[Joseph Gilbert Totten]]: December 7, 1838{{spaced ndash}}April 22, 1864
*[[Richard Delafield]]: April 22, 1864{{spaced ndash}}August 8, 1866

===Corps of Topographical Engineers===
{{main|United States Army Corps of Topographical Engineers}}
The Corps of Topographical Engineers had been established in 1831 with the mission of [[exploration]], [[surveying]], and [[cartography]], particularly in the [[American West]].  Topographical engineers (or "topogs") including [[John C. Frémont]], [[Howard Stansbury]], [[William H. Emory]] and [[Gouverneur K. Warren]] were instrumental in the westward expansion of the United States.<ref name="Baldwin27">Baldwin, p. 21-27</ref>  During the war, the civilian nature of the Corps' mission was largely suspended and it undertook the role of reconnaissance, construction of defensive works and supplying maps to the army.  In these conditions drawing a distinction between the two corps became increasingly impractical, until in March 1863 the Corps of Topographical Engineers was disbanded and its mission taken up by the Corps of Engineers.<ref name="Newell292"/>

The Topographical Engineers numbered forty-five officers before the Civil War.  In August 1861 an additional two lieutenant colonels, four majors and six lieutenants were authorized by Congress. There were no enlisted men in the Corps, although when the Corps was expanded Congress also authorized a company of engineers for the Topographical Engineers to be modeled after the Corps of Engineers.  However this company was never formed, and the actual size of the Corps shrank as a number retired, died, defected to the Confederacy or became general officers of the volunteers, until eventually the remaining officers were absorbed by the Corps of Engineers.<ref name="Newell292"/>

The most important role played by the Topographical Engineers, even after their merger with the regular Corps, was providing desperately-needed maps to army commanders.  Each field army headquarters established their own topographical departments under the supervision of engineer officers, which would provide the army with maps necessary for a given campaign.  Such departments themselves were staffed with teams of [[draughtsmen]] and assistants and stocked with [[printing press]]es, [[photographic]] and [[lithographic]] equipment.<ref name="Newell292"/>
;Leadership
The Chief of Topographical Engineers at the start of the Civil War was Colonel [[John James Abert]].  Colonel Abert had been responsible for lobbying Congress to make the Corps an independent branch of War Department and was appointed to lead his creation in 1838.  He retired in September 1861 and was replaced by [[Stephen Harriman Long]], who remained in the position until the Corps was disbanded.  Thereafter he continued to serve in the Corps of Engineers as the senior officer to the Chief Engineer.<ref name="Baldwin27"/><ref>Baldwin, p. 283</ref>

===Inspector General's Department===
{{main|Office of the Inspector General of the United States Army}}
At the start of the Civil War, there was technically no Inspector General's Department, with neither a set of operating practices or centralized direction.  Instead there were two [[Inspector General]]s (IGs) with the rank of colonel whose duty was to conduct inspections and investigations to ensure the army was organized and operating at full readiness, but these were done in an ad-hoc manner at the discretion of the Secretary of War.  As the war progressed and membership in the inspectorate increased, the duties of IGs and assistant IGs were continually redefined, to the extent that any time a problem was identified the common response was simply to assign an inspector to it.  Eventually in January 1863 a permanent office of the IG was established in Washington, and it was from here that the process of exerting a centralized control over IGs in the field and crafting standard policies and procedures was started.<ref name="Newell94">Newell & Shrader, p. 90–94</ref>

In August 1861, Congress authorized an increase of two additional IGs with the rank of colonel and five assistant IGs with the rank of major from among the regular army.  This number stayed the same throughout the entire war, with the addition of a small civilian clerical staff once the Washington office was established.  Congress eventually determined that each geographical department, army, corps, division and brigade would also be assigned an IG or assistant IG, however these positions were to be filled by regular or volunteer officers detailed from line units of the army or from the other staff departments.<ref name="Newell94"/>

The inspectorate faced many challenges during the Civil War, including hostility and lack of cooperation from some commanders and the mixed performance of some IGs in the field.  Despite these issues it was able to successfully meet the challenges of the war overall, particularly with bringing under control the waste, fraud and abuse which had been rampant at the start of the conflict.<ref name="Newell94"/>
;Leadership
At the start of the war the inspectorate consisted of Colonel [[Sylvester Churchill]], the senior IG of the army, and Colonel [[Joseph K. Mansfield]], the junior IG.  Churchill however took leave in April 1861 on account of his health and formally retired in September that year, while Mansfield was promoted to major-general and left to command troops in May.  Colonel [[Henry Lee Scott]] replaced Mansfield that same month, but when Churchill retired his position was given to Colonel [[Randolph Marcy]], father-in-law to George McClellan, in the same month.  Serving as the chief of staff to McClellan, Marcy did not formally take up his duties as senior IG until after the [[Battle of Antietam]], by which point however his association with McClellan had soured Marcy's relationship with Secretary Stanton, who sent him on inspection tours of various geographical departments.  Instead, the [[de facto]] leader of the inspectorate was whoever was the IG in charge of the Washington office, which was Colonel [[Delos Sacket]] between January 1863 and March 1864, and Colonel [[James Allen Hardie]] for the remainder of the war.<ref name="Newell94"/>

===Medical Department===
{{main|Medical Corps (United States Army)}}

The Army Medical Department (AMD) was rivaled only by the Quartermaster's Department in the scope and complexity of its responsibilities: caring for sick and wounded soldiers, operating [[field hospital|field]] and [[general hospital]]s, and acquiring and distributing medicine, medical equipment, hospital food and similar supplies.  Functions such as [[Casualty evacuation|evacuating]] soldiers off the battlefield or constructing hospitals were handled were handled by other departments, though later in the war the AMD assumed many of these roles.  In March 1864 it was placed in charge of casualty evacuation ([[U.S. Ambulance Corps]]) and the organization and operation of [[Train (military)|medical supply trains]].  In December it was given control over the construction and equipping of military hospitals, and of [[hospital train]]s and [[hospital ship]]s in February 1865.  Other responsibilities assumed during the war included care for disabled veterans and their families, prisoners of war, refugees and freed slaves; maintaining medical records of the dead and wounded; and preparing a medical and surgical history of the war. The AMD started out the war staffed by a conservative and inflexible leadership which negatively impacted its functioning, but would eventually be rectified by war's end.<ref name="Newell163">Newell & Shrader, p. 163–164</ref>

{|class="wikitable" style="float: right" 
! style="text-align:l center; background:#acc;" |Position
! style="text-align:l center; background:#acc;" |1862
! style="text-align:l center; background:#acc;" |1863
! style="text-align:l center; background:#acc;" |1864
! style="text-align:l center; background:#acc;" |1865
|-
|+Regular army medical personnel<ref>Newell & Shrader, p. 166</ref>
|-
|Surgeon General ([[Brigadier General (United States)|BG]])
|1
|1
|1
|1
|-
|Assistant Surgeon General ([[Colonel (United States)|COL]])
|1
|1
|1
|1
|-
|Medical Inspector General (COL)
|1
|1
|1
|1
|-
|Medical Inspector ([[Lieutenant Colonel (United States)|LTC]])
|8
|16
|16
|16
|-
|Surgeon ([[Major (United States)|MAJ]])
|50
|50
|50
|50
|-
|Assistant Surgeon ([[Captain (United States O-3)|CPT]])
|14
|5
|3
|
|-
|Assistant Surgeon ([[First lieutenant#United States|1LT]])
|100
|109
|111
|114
|-
|Medical Storekeeper
|6
|6
|6
|6
|-
|Medical Cadet
|70
|70
|70
|70
|-
|[[Hospital Steward]]
|201
|471
|650
|931
|-
|}

In April 1861 the AMD was the largest of the staff departments in the regular army: a [[Surgeon General of the United States Army|Surgeon General]] (with the rank of colonel), thirty surgeons, eighty-three assistant surgeons, and fifty-nine [[Hospital Steward]]s.  However this number was barely adequate to meet the needs of the army in peacetime, and in May 1861 an additional ten surgeons and twenty assistant surgeons were added to cover the new regular army regiments being raised.  Later that year in August, Congress authorized the appointment of fifty medical [[cadet]]s to be chosen from young men with a liberal education and prior medical experience.  They had the rank and pay of West Point cadets and were to act as [[ambulance attendant]]s in the field and assistants in general hospitals.<ref name="Newell166">Newell & Shrader, p. 168–177</ref>

In April 1862, Congress authorized a substantial reorganization of the AMD.  Beyond promoting the surgeon general to brigadier general and adding additional staff, one of the most controversial was the introduction of medical inspectors, as a number of these were appointed by Secretary Stanton for "political" purposes.  Charged with supervising all aspects of sanitary conditions within the army, their purview included the inspection of quarters, camps, hospitals and transports; their duties were later expanded to include issuing certificates of [[Military discharge|discharge]] for reasons of disability.  Congress also gave the surgeon general the authority to hire as many hospital stewards as necessary, and a month later they authorized the addition of six trained [[apothecaries]] and [[druggists]] as medical storekeepers.<ref name="Newell166"/>

Most regular army medical officers served in staff positions, whether at the office in Washington or out in the field as regimental surgeons, [[attending physician]]s in general hospitals, medical purveyors who ran medical supply depots and laboratories, or as the medical director of a division, corps, field army or military department.  Medical directors oversaw the operation of field hospitals and the associate medical personnel, field sanitation and medical supply within their command.  However, there was no statutory basis for their assignment, and it wasn't until February 1865 when Congress bowed to pressure and provided for officers serving in these capacities to receive rank, pay and emoluments appropriate to their responsibilities.<ref name="Newell166"/>

Added to the relatively small number of regular army medical personnel were a further 546 surgeons and assistant surgeons volunteers, appointed by the president to supplement regular army personnel in staff positions; another 5,532 civilian doctors employed under contract (mainly in general hospitals) as acting assistant surgeons; a small number of medical officers of the [[Veteran Reserve Corps]]; and the thousands of regimental surgeons and assistant surgeons appointed to the volunteer regiments by their respective state governors.  Thousands more civilians were employed by the AMD as nurses, clerks, hospital attendants, laborers, etc.  The AMD was further augmented by a number of private and semi-official philanthropic organizations, foremost among which was the [[United States Sanitary Commission]] (USCC).<ref name="Newell166"/>

The chaotic aftermath of the first Battle of Bull Run – no coordination between field hospitals and casualty evacuation, regimental surgeons refusing to treat soldiers from other units, and the few ambulance drivers robbing their charges or fleeing – exemplified the inadequacies of pre-war planning and preparations.  Burdened with an aged and conservative leadership, it took the injection of more enlightened leaders to make the necessary reforms for the AMD to meet these new challenges.  By the war's end, the AMD had implemented a better method of evacuating battlefield casualties to field hospitals and general hospitals, established laboratories to test and certify drugs and other medicines, identified reliable sources of supply and implemented effective contracting procedures, and increased the number of medical personnel to see to the needs of over a million men under arms.<ref name="Newell192">Newell & Shrader, p. 188–192</ref>

Some challenges remained however, against which only small progress was made.  Although improved [[field sanitation]] reduced disease rates and some advances like the use of [[chloroform]] proved helpful, a lack of [[aseptic surgery]] or general understanding of the [[germ theory]] led to many deaths from disease, [[Shock (circulatory)|shock]] or [[secondary infection]].  [[Psychological trauma]] was not well understood and the average soldier made due with an inadequate diet for maintaining their health.  The AMD's reliance on the Quartermaster and Subsistence departments for transportation and rations respectively left these subject to interdepartmental rivalry until late in the war, and personal conflict between military commanders and their supporting medical personnel could lead to problematic health outcomes.  Despite these faults, AMD personnel did their best to alleviate the suffering of their fellow soldiers and laid the groundwork for future improvement.<ref name="Newell192"/>

;Leadership
The Surgeon General at the start of the war was Colonel [[Thomas Lawson (military physician)|Thomas Lawson]], who at 97 years was on his deathbed and his duties were being carried out Major Robert C. Wood, one of his assistants.  When he passed in May 1861 Lawson was succeeded by [[Clement Finley]], another old soldier who was characterized by contemporaries as "utterly ossified and useless".  Finley was slow to act, failed to reform the AMD to address the needs of the war, and particularly opposed to the use of female nurses.  He was forced to retire by Secretary Stanton in April 1862 and replaced with [[William A. Hammond]], who immediately went about reorganizing the AMD, eliminating [[red tape]] and promoting competent young men to positions of authority.  His strong independent streak also earned the enmity of Secretary Stanton, who in September 1863 sent him on an extended tour of the western theater and made Colonel [[Joseph Barnes (American physician)|Joseph Barnes]] the acting Surgeon General.  When Hammond was arrested, court-martialed and dismissed in August 1864, Barnes was promoted to fill his position.  Barnes remained the Surgeon General until after the war's end and succeeded in continuing Hammond's reforms by maintaining an excellent relationship with Secretary Stanton.<ref>Newell & Shrader, p. 164–166</ref>

===Ordnance Department===
{{main|United States Army Ordnance Corps}}
The principal mission of the Ordnance Department (ORDD) during the Civil War was the development, procurement, storage, distribution and repair of all army [[List of weapons in the American Civil War|ordnance]] and ordnance-related equipment such as [[limbers and caissons]] and [[accoutrements]].  It was also responsible for the procurement of horses to pull artillery until June 1861 when the Quartermaster Department took over that job.  The department faced challenges during the war, particularly during the early months as it struggled to arm the vastly expanded Union army whilst traitorous forces seized control of a number of arsenals and depots.  Eventually it was able to resolve many of these challenges and succeeded in providing thousands of [[field artillery]] pieces and millions of [[small arms]] for the Union army.<ref name="Eicher64"/><ref>Newell & Shrader, page 119</ref><ref name="USAL200">United States Army Logistics (1997), pages 199–200</ref>

When the Civil War began the Ordnance Department was commanded by a Chief of Ordnance and authorized forty officers, many in command of the army's arsenals and depots; fifteen ORDD military storekeepers; seventy [[ordnance sergeant]]s, often placed in supervisory roles including command of some depots and arsenals; and four hundred enlisted men, most of whom were employed as technicians at the armories and arsenals.  Hundreds of civilians were also employed, not only as clerks and laborers but also technicians and supervisors.  There were also [[Armed-forces artificer|artificiers]] on the rolls of the army's artillery regiments who were responsible for the maintenance of weapons within their regiments.<ref name="Newell127">Newell & Shrader, p. 122-127</ref>

Even in peacetime the size of the ORDD was insufficient, as fifty-six officers alone would've been required to bring the arsenals to their full authorized strength, and it proved inadequate once the war began.  In August 1861 Congress increased the authorized number of officers to forty-five: the Chief of Ordnance (brigadier general), two colonels, two lieutenant colonels, four majors, twelve captains, twelve first lieutenants, and twelve second lieutenants.  This still was not enough, and so in March 1863 an additional lieutenant colonel, two majors, eight captains and eight first lieutenants were added, bringing the authorized strength to sixty-four officers where it would remain for the rest of the war.  The number of ordnance sergeants and enlisted personnel were similarly increased on a yearly basis, until by 1865 they numbered 163 and 560 respectively, and the civilian staff was likewise increased.<ref name="Newell127"/>

In the field, each regiment was authorized an ordnance officer (to be chosen from among the unit's lieutenants) who, assisted by an ordnance sergeant, saw to the requisition and issuing of arms to the troops and management of the regimental ammunition [[Train (military)|train]]. For brigades and higher echelons of command, an ordnance officer was authorized to serve on the unit's staff with similar responsibilities. However unlike with the other supply departments, the ordnance department did not commission any volunteer officers to this role, instead relying on ORRD officers or (at division level and below) relying on regular officers filling the role as acting ordnance officers or combining the role with the assigned quartermaster.<ref name="Newell127"/>

The ORDD maintained a number of arsenals, armories and depots, where the majority of the army's arms, ammunition and other ordnance-related supplies were manufactured and/or stored. A number were seized before or at the war's outbreak, but more were created after fighting began and existing ones were expanded. By the middle of the war, the largest arsenals employed between one and two thousand civilians each. A substantial number of these employees were women and children, partly because they could be paid less than adult male workers, their small hands were thought to be better suited to assembling [[Cartridge (firearms)|cartridges]], and women were believed to be more safety-oriented.  Their line of work was dangerous for obvious reasons, and a number died in accidental explosions during the war. In the single-worst accident of the war, the [[Allegheny Arsenal#Explosion|explosion at the Allegheny Arsenal]], 70 of the 78 victims were women and girls.<ref name="Newell127"/>

{|class="wikitable" style="display: inline-table;" 
! style="text-align:center; background:#acc;" |Name
! style="text-align:l center; background:#acc;" |Location
! style="text-align:l center; background:#acc;" |Established
! style="text-align:center; background:#acc;" |Notes
|-
|+United States Arsenals, Armories and Depots<ref name="Eicher64">Eicher, p. 63-64</ref><ref>Beers, H. P., Munden, K. W. (1998). The Union: A Guide to Federal Archives Relating to the Civil War. Washington: National Archives and Records Administration. p. 284-287</ref><ref>Newell & Shrader, p. 124</ref>
|-
|[[Springfield Armory]]
|[[Springfield, MA]]
|1794
|Principal US Army armory
|-
|[[Harpers Ferry Armory]]
|[[Harper's Ferry, WV|Harper's Ferry, VA]]
|1796
|Destroyed April 1861, seized by [[Confederate States Army|CSA]] 
|-
|[[Allegheny Arsenal]]
|[[Pittsburgh, PA]]
|1814
| 
|-
|[[Watervliet Arsenal]]
|[[Watervliet, NY]]
|1814
| 
|-
|[[Champlain Arsenal]]
|[[Vergennes, VT]]
|1816
|Discontinued 1855, reestablished 1861
|-
|[[Frankford Arsenal]]
|[[Philadelphia|Philadelphia, PA]]
|1816
|
|-
|[[Rome Arsenal]]
|[[Rome, NY]]
|1816
|
|-
|[[Bellona Arsenal]]
|[[Richmond, VA]]
|1816
|Discontinued 1835, seized by Virginia April 1861
|-
|[[Washington Arsenal]]
|[[Washington, D.C.]]
|1816
|
|-
|[[Watertown Arsenal]]
|[[Watertown, MA]]
|1816
|
|-
|[[Pikesville Arsenal]]
|[[Pikesville, MD]]
|1819
|
|-
|[[Augusta Arsenal]]
|[[Augusta, GA]]
|1826
|Seized by Georgia militia January 1861
|-
|[[Baton Rouge Arsenal]]
|[[Baton Rouge, LA]]
|1826
|Seized by Louisiana militia January 1861
|-
|[[Kennebec Arsenal]]
|[[Augusta, ME]]
|1827
|
|-
|[[St. Louis Arsenal]]
|[[St. Louis, MO]]
|1827
|
|-
|[[Mount Vernon Arsenal]]
|[[Mount Vernon, AL]]
|1829
|Seized by Alabama militia January 1861
|-
|[[Detroit Arsenal (Dearborn)|Detroit Arsenal]]
|[[Dearborn, MI]]
|1832
|
|-
|[[Apalachicola Arsenal]]
|[[Apalachicola, FL]]
|1833
|Seized by Florida militia January 1861
|-
|[[Governors Island#Mid-19th century and Civil War|New York Arsenal]]
|[[Governors Island]], [[New York (state)|NY]]
|1836
|
|-
|[[Fayetteville Arsenal]]
|[[Fayetteville, NC]]
|1836
|Seized by North Carolina militia April 1861
|-
|[[Little Rock Arsenal]]
|[[Little Rock, AR]]
|1837
|Seized by Arkansas authorities February 1861
|-
|[[Fort Monroe|Fort Monroe Arsenal]]
|[[Old Point Comfort]], [[Virginia|VA]]
|1838
|
|-
|[[Charleston Arsenal]]
|[[Charleston, SC]]
|1841
|Seized by South Carolina militia December 1860
|-
|[[Fort Leavenworth|Leavenworth Arsenal]]
|[[Leavenworth, KS]]
|1847
|
|-
|[[Benicia Arsenal]]
|[[Benicia, CA]]
|1851
|
|-
|San Antonio Arsenal
|[[San Antonio, TX]]
|1855
|Seized by Texas militia February 1861
|-
|[[Fort Vancouver National Historic Site|Vancouver Arsenal]]
|[[Fort Vancouver]], [[Washington (state)|WA]]
|1859
|
|-
|[[Fort Union National Monument|Fort Union Arsenal]]
|Fort Union, [[New Mexico|NM]]
|1860
|
|-
|Louisville Depot
|[[Louisville, KY]]
|1861
|
|-
|Nashville Depot
|[[Nashville, TN]]
|1862
|
|-
|[[Columbus Arsenal]]
|[[Columbus, OH]]
|1863
|
|-
|Indianapolis Arsenal
|[[Indianapolis, IN]]
|1863
|
|-
|[[Rock Island Arsenal]]
|[[Rock Island, IL]]
|1863
|
|-
|}

The ORDD faced an immediate crisis when the war began as it was suddenly responsible for arming the rapidly-expanding number of troops being brought into Federal service. This job was made more difficult by actions taken by Secretary of War [[John B. Floyd]] before the war, when he ordered the transfer of large numbers of arms from Northern to Southern arsenals and the sale of Federal arms to various Southern states.<ref name="Newell135">Newell & Shrader, pages 127–135</ref>  When the Southern states did seize the arsenals within their territory, in addition to the gun-making equipment at Harper's Ferry they were able to acquire about 159,000 small arms, 429 cannons, and 4.5 million rounds of small arms ammunition.<ref name="USAL200"/>  ORDD was forced to make up the immediate shortfall by contracting with private companies or purchasing from European powers; many weapons bought under contract proved to be inferior to government standards or sold at inflated prices, while European governments were happy to get rid of their obsolete weapons.  Eventually the fraud and corruption was brought under control and ORDD was able to bring its arsenals' productions levels up to where they could meet the army's need. This can be seen with the rapid expansion of the Springfield Armory, which before the war averaged 800 muskets a month but by January 1863 was producing 24,000 muskets and rifles a month.<ref name="Newell135"/>

A more persistent issue faced by ORDD were efforts by members of Congress, the general public, and even President Lincoln to get them to adopt many new military technologies, particularly [[breechloader|breech-loading]] and [[repeating rifle]]s like the [[Spencer repeating rifle|Spencer]] and [[Henry rifle]].  The department's senior leadership was unwilling to wholeheartedly embrace this technology without extensive field testing, and worried over delays from retooling manufacturing equipment and other logistical concerns that went with their adoption.  Nevertheless, a limited number of these weapons were purchased and distributed to troops in the field, and trials were undertaken to determine which one would become the army's standard rifle for general use, although these weren't completed until well after the war ended.<ref name="Newell135"/>

After the war ORDD came under harsh criticisms, particularly over their conservatism in regards to new technology.  However it did meet the challenge of equipping the Union army with many modern weapons and other materiel.  From the beginning of the war to the end, Federal arsenals produced 7,892 cannons with over six million artillery [[Shell (projectile)|shot and shell]] and six million pounds of [[grapeshot]] and [[canister shot]]; more than 4 million small arms with over a billion rounds of small arms ammunition; over 13,000 tons of gunpowder and 45,000 tons of lead; and nearly 3 million complete sets of infantry and cavalry accoutrements and horse equipment.<ref name="Eicher64"/><ref name="Newell135"/>

;Leadership
[[Henry K. Craig]] was the Chief of Ordnance when the Civil War began, having served in that position since 1851.  Craig received much of the blame for the poor state of affairs at the time, and angered many special interests by resisting the purchase of new and untested weapons in favor of increasing arsenal production and limiting purchases to reputable domestic and international sources.  His obstinate behavior saw Craig relieved and replaced with [[James Wolfe Ripley]] on April 23, 1861.  However Ripley was similarly resistant to these same private contractors and their Congressional backers, particularly with adopting breech-loading rifles, and so was forced to retire on September 15, 1863.  His replacement, [[George D. Ramsay]], was more open to the new weaponry but did not have the confidence of Secretary Stanton, who inserted Captain George T Balch into Ramsay's headquarters to "call the shots".  Ramsay endured this situation until forced to retire on September 12, 1864. [[Alexander Brydie Dyer]] took over as Chief of Ordnance and served out the remainder of the war heading the department. While resistant to the lobbyists like his predecessors, Dyer was a more enthusiastic proponent of breech-loading and repeating rifles. He was also more bureaucratically adept and able to remain on good terms with Secretary Stanton.<ref>Newell & Shrader, pages 109–110</ref>

===Pay Department===
{{main|Finance Corps}}
The Pay Department had the responsibility of accounting for, maintaining records regarding, and disbursing of funds for payment to army personnel, including allowances and bounties, as well as settling claims against the government related to pay and allowances. It was not however responsible for payments on contracts and other obligations incurred by the Army as those were handled by the respective department. Payments to officers and soldiers was supposed to be made on a bi-monthly basis, although circumstances might see these delayed significantly (as much as by eight months in some cases).<ref name="Newell104">Newell & Shrader, pages 98–104</ref>

As originally organized the Pay Department was headed by a paymaster general with the rank of colonel, two deputy paymasters general with the rank of lieutenant colonel, and twenty-five paymasters with the rank of major. There were also a small number of civilian clerks, but no enlisted personnel assigned to the department. Cash was received directly by the paymaster general from the [[United States Department of the Treasury|Treasury Department]] and forwarded to the supervising paymaster of a given "pay district" or field headquarters. These funds were then distributed under armed guard to the officers and soldiers within the pay district. Pay districts generally coincided with the boundaries of military divisions, departments and districts, which as the army grew the number and size of pay districts grew likewise. This required the appointment of more paymasters during the course of the war and an increase in the number of civilian clerks, the latter of which reached a peak of 155 by 1864.<ref name="Newell104"/>

The rapid increase in the size of the army presented a significant challenge to the Pay Department, as the number of soldiers needed to be paid was over fifty times greater than the pre-war size.  This was particularly the case for sick and wounded soldiers who were separated from their units and so harder to located.  However while payments were occasionally delayed, it never got to the point where soldiers felt compelled to mutiny as had been done during the [[American Revolutionary War|Revolution]]. In the four years and four months of the Civil War, the Pay Department disbursed $1,029,239,000 of which $541,000 was lost due to embezzlements and other causes, at an expense of $6,429,600.<ref name="Newell104"/>

;Leadership
When the Civil War began, Colonel [[Benjamin F. Larned]] served as Paymaster General but was in poor health.  He was temporarily relieved of duty in July 1862 due to illness and would die a few months later. From July until December of that year, Major Cary H. Fry served as the acting Paymaster General, when [[Timothy Andrews (general)|Timothy Andrews]] was appointed to the position.  He would remain in that position until retiring in November 1864, when [[Benjamin Brice]] was appointed in his place and finished out the war as Paymaster General.  Both Andrews and Brice argued that the position of Paymaster General should made a brigadier general and the number and rank of subordinate paymasters similarly increased, commensurate with the type of expansion other administrative departments experienced during the war, but their recommendations were ignored.<ref name="Newell104"/>

===Provost Marshal General's Bureau===
{{main|United States Army Provost Marshal General}}
The Provost Marshal General's Bureau (PMGB) was created to oversee the apprehension of deserters, conduct [[counterespionage]], and recover stolen government property.  Originally established as an office of the AGD in September 1862, it was made an independent department in May 1863 as part of the Conscription Act of 3 March 1863.  The Conscription Act also made it responsible for the administration of the draft system, with two other responsibilities added later that year: first with the management of the [[Invalid Corps]] in April, and then the recruitment of white volunteers in May.  Intended only as temporary organization for the duration of the war the PMGB was effectively terminated in August 1866, whereupon all records, funds and responsibilities were transferred to the AGD.<ref name="Eicher58"/><ref name="Newell106">Newell & Shrader, pages 104–106</ref>

Initially consisting of a single officer, the provost marshal general (PMG) himself, eventually the bureau was authorized fourteen additional officers split between several branches. However, a mix of officers from the regulars, volunteers, and Invalid Corps were also detailed to the PMGB to fulfill a number of rolls. Each congressional district was appointed a provost marshal who served on a "board of enrollment". The board included two other persons (one of whom was to be a licensed physician) and was charged with overseeing the enrollment of men for the draft. An enrolling officer could also be appointed per subdistrict (town, township or ward) on a temporary basis, as could special agents tasked with apprehending deserters.  Additionally, all provost marshals and special agents were empowered to arrest any stragglers and send them to the nearest military post. By November 1864 the PMGB (not counting the Invalid Corps) included 4,716 officers and employees.<ref name="Newell106"/>

In the aggregate, the PMGB was successful in the enrollment and maintenance of sufficient manpower for the Union army.  Over one million men were brought into the Union army at a cost of $9.84 per man (versus $34.01 per man prior to the bureau's formation) and the arrest and return to duty of over 76,500 deserters. The bureau was also able to raise $26 million to fully fund its enrollment and draft duties.<ref name="Newell106"/>

;Leadership
When originally created as an office of the AGD, Colonel Simeon Draper was named the Provost Marshal General, which he held from October 1862 to March 1863.  However, the PMGB did not live up to expectations under Draper's leadership.  When it was made an independent department he was replaced with [[James Barnet Fry]], who served as the PMG until the bureau's dissolution.<ref name="Newell106"/>

===Quartermaster's Department===
{{main|Quartermaster Corps (United States Army)}}
The Quartermaster's Department (QMD) was the most important and extensive department of the Union army, not least because it provided transportation services to the entire army, including the other supply departments.  The QMD was responsible for the procurement, storage and distribution of supplies not already covered by another supply department, including various [[equipage]] (clothing, tents, stoves, etc.), horses and mules ([[United States Army Remount Service#Early history|Cavalry Bureau]]), [[forage]] and [[fuel]], and non-Ordnance vehicles including wagons, ambulances and [[traveling forge]]s.  Other assumed responsibilities included the acquisition, construction and maintenance of various military structures such as barracks, hospitals, wharves, storehouses, etc.; the charter, purchase and maintenance of all [[riverine]] and [[ocean-going vessel]]s used by the army and the [[Western Gunboat Flotilla]]; the construction, maintenance and management of all military railroad transportation ([[United States Military Railroad]]); the construction, maintenance and management of military telegraph lines ([[U.S. Military Telegraph Corps]]); management of all [[Train (military)|wagon trains]] in the field; the collection and burial of the dead and maintenance of [[United States National Cemetery System|national cemeteries]]; and any expenses associated with army movement and operations that did not fall under another department's purview.<ref name="Newell139">Newell & Shrader, page 139</ref><ref name="Eicher61">Eicher, pages 60–61</ref>

The QMD at the start of the war consisted of just thirty-seven officers, seven military storekeepers, and thirteen civilian clerks at the office of the Quartermaster-General (QMG), a situation which was considered understaffed even for peacetime requirements. Within a month of the conflict's start, Congress passed an act to raise the number of officers to forty-nine, and again several months later it was raised to seventy-six, adding an assistant quartermaster-general (colonel) and additional numbers of deputy quartermaster-generals (lieutenant colonel), quartermasters (major) and assistant quartermasters (captain) to support the QMG (brigadier-general). Although a substantial increase, this was not enough to meet the needs of the QMD, and so more than nine hundred assistant quartermasters of volunteers were commissioned and a large number of regular and volunteer officers were detailed to serve as acting quartermasters during the war. Congress also authorized the number of storekeepers increased to twelve and the hiring of additional clerks and other civilian workers for the office (including women), which would grow to over 200 by 1863 and close to 600 by the war's end. To this were added the many civilians working at the quartermaster depots or with quartermasters in the field. Many of these workers were rowdy and difficult to manage, especially before Congress made QMD employees subject to military law and discipline. One exception were Black workers who proved more reliable and whom Quartermaster-General Meigs considered a great aid; by 1864 the QMD was largely reliant on them to fulfill various unskilled positions.<ref name="Newell142">Newell & Shrader, pages 142–151</ref>

Officers of the QMD were assigned as commanders of the various quartermaster depots or to the staff of various field units (with the exception of regiments, whose quartermaster personnel were selected from among its own officers and NCOs).  Depot commanders were responsible for the acquisition, storage and distribution of supplies and the disbursement of funds for transportation and other services. Supplies could be manufactured within the depot or purchased from commercial interests, usually as part of a low-bid contract but in an emergency on the open market. In the first three years of the war depot commanders themselves were responsible for managing these contracts, but by July 1864 a more centralized system requiring approval from the QMG's office had been implemented to improve accountability. Based on unit quartermasters' requests, supplies would be shipped to advanced depots or railheads, where the unit quartermasters arraigned to have them picked up and issued to the unit.<ref name="Newell142"/><ref name="USAL202">United States Army Logistics, pages 202–204</ref>

The principal depots of the QMD were located in [[Cincinnati]], [[Milwaukee]], [[New York City|New York]], [[Philadelphia]], [[Quincy, Illinois]], [[Steubenville, Ohio]], [[St. Louis]], and [[Washington, D.C.]],<ref name="Eicher61"/> with other major depots located in [[Baltimore]], [[Chicago]], [[Louisville, Kentucky|Louisville]], [[New Orleans]], and [[San Francisco]].<ref name="USAL202"/> New York, Philadelphia, and Washington were the primary depots supporting Union armies in the eastern theater, with Cincinnati, St. Louis, and Louisville the primary support depots in the western theater. Many advanced and temporary depots were established as needed, including at [[Alexandria, Virginia]], Fort Monroe, [[City Point, Virginia]], and Nashville, which could become as large and busy as any general depot.  However, despite these depots being responsible for thousands of soldiers and millions of dollars in supplies, many of their commanders were only captains.  Congress approved in July 1864 the appointment of ten depot commanders to the rank of colonel, while other commanders either received a volunteer commission or brevet rank of brigadier general for as long as they remained at their depot.<ref name="Newell142"/>

In the early months of the conflict, the QMD struggled to clothe, equip and transport the rapidly-growing Union army, especially as fraud, war profiteering and political interference was rampant.  Under the able leadership of Quartermaster-General Meigs and legislation passed by Congress, this corruption was quickly brought under control and most quartermasters (with notable exceptions such as [[Justus McKinstry]]) proved to be able and law-abiding.<ref name="Newell151">Newell & Shrader, pages 151–161</ref> Undoubtedly this was due in part to the requirement that quartermasters file a [[Bond (finance)|bond]] worth $10,000 that made them personally liable for their supplies. The exception to this was when the supplies were destroyed due to natural causes or to prevent them falling into enemy hands, a situation which perversely caused celebration among some quartermasters.<ref>Hess, E. J. (2017). Civil War Logistics: A Study of Military Transportation. United States: LSU Press. page 22</ref>  While there were inevitably mistakes and other mishaps, the Union army was rarely deprived of the supplies and services provided by the QMD. Although the scope and scale of the Civil War was beyond any prewar planning, the professional competence of the department allowed it to quickly meet every challenge.  It also exploited emerging technologies like railroads and steamboats with expertise to support the Union army like never before at a strategic and operational level.<ref name="Newell151"/>

Of the $1.8 billion spent by the Federal government during the war, over a billion of that was distributed by the Quartermaster Department.<ref>Hess (2017), page 30</ref>  Among the staggering number of supplies and services acquired by the QMD include approximately a million horses and half a million mules; the movement by rail of over 1.2 million troops; 590 ocean-going vessels under charter or owned outright providing over 190,000 tons of shipping, with another 599 riverine vessels; over 1.6 million tons of coal and 500,000 [[Cord (unit)|cords]] of wood; over 22 million [[bushel]]s of corn, 78 million of oat, 1.5 million tons of hay and 21,000 tons of straw and other fodder; more than $23 million for the rental, construction and maintenance of army property; and over 51,000 standard army wagons and 5,300 ambulances.<ref name="Newell151"/>

;Leadership
The Quartermaster General at the start of the war was [[Joseph E. Johnston]], who resigned shortly after on April 22, 1861, to join the Confederate army. Major Ebenezer S. Sibly served as acting QMG until [[Montgomery C. Meigs]] was appointed and took up his new duties on June 13, 1861. Considered one of the most effective leaders to serve in the Union army, Meigs oversaw the expansion of the QMD to meet the demands of the war and continued to lead it well after its end. Meigs was also a [[hands-on management|hands-on manager]] and from August 1863 to January 1864 he was busy handling logistical matters in the western theatre. During his absence, Colonel [[Charles Thomas (1797–1878)|Charles Thomas]] served as acting QMG in Washington.<ref>Newell & Shrader, page 140</ref>

===Signal Corps===
{{main|Signal Corps in the American Civil War}}
The creation of a [[Signal Corps (United States Army)|Signal Corps]] for the US Army was the result of [[Albert James Myer]], an army surgeon who had developed a system of [[military signals]] based on [[sign language]] known as [[Wigwag (flag signals)|wigwag]].  Myer was appointed to the rank of major and to lead the Signal Corps (albeit as its only officer) effective June 27, 1860.  During the early years of the Civil War the Signal Corps did not have any personnel other than Myer appointed to it.  Instead, officers and enlisted men were sent from other units to [[Fort Monroe]] to learn his system and in turn teach others.  Myer continued to campaign for a more formal and permanent Signal Corps, which was finally granted by Congress on March 3, 1863.  However, a dispute between the Signal Corps and the [[U.S. Military Telegraph Corps]] over who controlled [[electrical telegraph]]y led Secretary Stanton to replace Myer with Maj. William Nicodemus in November of that year.  After an inadvertent release of confidential information, Nicodemus was in turn replaced by Colonel Bejamin Fisher, who would remain the Corps' commander until the end of the war.  The Signal Corps proved instrumental in coordinating the actions of the Union army during the Civil War and afterwards Congress appointed Myers to once again lead it in 1866.<ref name="Newell303">Newell & Shrader, pages 292–303</ref>

===Subsistence Department===
The mission of the Subsistence Department was the purchase, storage and distribution of [[Foods of the American Civil War|rations]] and related items in a timely manner. It was the smallest of the four supply departments, and even as the army grew to encompass over a million soldiers the department itself barely expanded in size.  Yet it was able to meet its mission to such an extent that President Lincoln once remarked to an officer "Your department we scarcely hear of; it is like a well-regulated stomach, works so smoothly we are not conscious of having it."<ref name="Newell111">Newell & Shrader, pages 109–111</ref>

The authorized strength of the department at the war's start was a Commissary General of Subsistence (CGS) with the rank of colonel, an assistant CGS with the rank of lieutenant colonel, and ten commissaries of subsistence (CS), two with the rank of major and the rest captains. Those not assigned to work at the office of the CGS in Washington were in charge of one of the subsistence depots or purchasing offices, or assigned to the staff of one of the military departments. Although there were no enlisted personnel in the department (all commissary positions at the regimental level being fulfilled by members of the regiment), a small civilian staff of clerks and laborers was assigned to the department.<ref name="Newell111"/>

To meet the needs of feeding the rapidly-expanding Union army, Congress authorized a CS with the rank of captain to be assigned to each brigade in July 1861, and in August 1861 the department was expanded with twelve additional officers, four majors and eight captains. A year later when army corps were officially created a CS with the rank of lieutenant colonel was authorized to serve on their staff, and in February 1863 the department was further expanded when the CGS was promoted to brigadier general, a second assistant CGS was added with the rank of colonel, and two additional majors were authorized.  Eventually in March 1865 Congress formally recognized wartime requirements by authorizing a chief CS with the rank of colonel for each field army, military department and division, and principle subsistence depot; an assistant CS with the rank of colonel assigned to Washington; up to six CS with the rank of lieutenant colonel to serve as inspectors or special duty assignment; a chief CS with the rank of lieutenant colonel for each army corps; and a CS with the rank of major for each division.<ref name="Newell111"/>

The need to fill CS positions among the field units primarily came from volunteer officers or regular officers detailed to the duty, and by the end of the war there were 535 commissaries of subsistence of volunteers, bringing the total complement of officers in the department to 564.<ref name="Newell111"/> Although educating them in the principles of their duty was a constant problem, it was a minor one eventually fixed with time and experience, and those who could not meet the standards of the department were relieved of duty.<ref name="Newell118"/>

During the war the principle subsistence depots and purchasing offices were located in Baltimore, [[Boston]], Chicago, Cincinnati, Louisville, Philadelphia, St. Louis, San Francisco and Washington, D.C.  Depot commissaries, assisted by civilian clerks and laborers, received purchases in bulk at these locations and repackaged them for shipment to armies in the field.  The actual transportation of rations was handled by the Quartermaster Department, requiring close cooperation between the two.  Major beef depots were also established in Alexandria, Virginia, Louisville and Washington. During the war the department developed a highly effective system of base, advanced, and temporary depots, and mobile beef herds which followed behind Union forces in the field.<ref name="Newell118">Newell & Shrader, pages 112–118</ref><ref name="USAL202"/>

The success of the Subsistence Department in meeting the challenges of the war was noted by Secretary Stanton, who observed in 1865 that no operation conducted by the Union army failed on account of the department being unable to meet its obligations.  In total, the department purchased over $361 million in foodstuff and miscellaneous subsistence items from July 1, 1861, to June 30, 1865.  The vast quantities of items managed by the department included over 504 million pounds of hardtack, 223 million pounds of bacon, 200 million pounds of brown sugar, 106 million pounds of fresh beef, 64 million pounds of roasted coffee and more than 322,000 live beef cattle.<ref name="Newell118"/>

;Leadership
At the Civil War's start, the CGS was [[George Gibson (Commissary General)|George Gibson]]. Gibson, who at eighty-six was the oldest serving officer in the army, had been in this position since the department was first created in April 1818 and as such was responsible for establishing its procurement and distribution methods. When he died on September 29, 1861, he was succeeded by his deputy, [[Joseph Pannell Taylor]]. Taylor oversaw the department's expansion during the most eventful years of its history and served until his death on June 29, 1864.  The senior assistant CGS [[Amos Beebe Eaton]] was promoted to the position upon Taylor's death and served as CGS for the rest of the war.<ref name="Newell111"/>