[5] Almost 200 United States Military Academy graduates who previously left the U.S. Army, including Ulysses S. Grant, William Tecumseh Sherman, and Braxton Bragg, returned to service at the outbreak of the Civil War.

It turned out that the war itself proved to be much longer and far more extensive in scope and scale than anyone on either side, Union North or Confederate South, expected or even imagined at the outset on the date of July 22, 1861.

[28] At The Wheatfield during the Battle of Gettysburg, the regulars' fighting skill and orderly retirement under fire drew the admiration of many observers, including Prince Philippe, Count of Paris.

[74] Native-born White Americans made up roughly two-thirds of the soldiers in the Union army, with the rest of many different ethnic groups, including large numbers of immigrants.

Popularly-held prejudices doubted whether Black people could be effective soldiers, and President Lincoln believed allowing their enlistment would anger Northern whites and alienate not just the South but the Border States too.

For the women who served, nursing during the Civil War was a hazardous occupation: grueling hours spent in close proximity to deadly diseases and nearby battlefields resulted in many suffering permanent disabilities or death.

Tens of thousands of women served as nurses for the Union army, among whom are included Clara Barton, Susie King Taylor, Mary Edwards Walker, and Louisa May Alcott.

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.

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.

[102] 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.

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.

[103] 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.

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.

Instead there were two Inspector Generals (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.

[115] 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.

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.

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 the acting Surgeon General.

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.

[121] 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.

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.

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.

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.

[129] 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.

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.

[136] The tactics of the Union army, as with their Confederate opponents, was derived from traditions developed in Europe around the use of smoothbore muskets: soldiers marching shoulder-to-shoulder in lines, columns and other formations in order to deliver volley fire on the enemy.

More recently, historians have questioned this narrative and argued based on research that most combat still took place at the range of smoothbore muskets and casualty rates were little different from during the Napoleonic Wars.

[149] Stirred up by the instigating rhetoric of Democratic politicians,[150] the Irish had shown the strongest support for Southern aims prior to the start of the war and had long opposed abolitionism and the free black population, regarding them as competition for jobs and blaming them for driving down wages.