During the American Civil War, the United States Army, the land force that fought to preserve the collective Union of the states, was often referred to as the Union army, Federal army, or Northern army. It proved essential to the restoration and preservation of the United States as a working, viable republic.
The Union army was made up of the permanent regular army of the United States, but further fortified, augmented, and strengthened by the many temporary units of dedicated volunteers, as well as including those who were drafted in to service as conscripts. To this end, the Union army fought and ultimately triumphed over the efforts of the Confederate States Army.
Over the course of the war, 2,128,948 men enlisted in the Union army, including 178,895, or about 8.4% being colored troops; 25% of the white men who served were immigrants, and a further 18% were second-generation Americans. 596,670 Union soldiers were killed, wounded or went missing during the war. The initial call-up in 1861 was for just three months, after which many of these men chose to reenlist for an additional three years.
Formation
When the American Civil War began in April 1861, the U.S. Army included ten regiments of infantry, four of artillery, two of cavalry, two of dragoons, and one of mounted rifles. The regiments were scattered widely. Of the 197 companies in the U.S. Army, 179 occupied 79 isolated posts in the West, and the remaining 18 manned garrisons east of the Mississippi River, mostly along the Canada–United States border and on the U.S. East Coast. There were only 16,367 servicemen in the U.S. Army, including 1,108 commissioned officers. Approximately 20% of these officers, most of them Southerners, resigned, choosing to tie their lives and fortunes to the Confederate army.
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. This group's loyalties were far more evenly divided. Clayton R. Newell (2014) states, 92 wore Confederate gray and 102 put on the blue of the United States Army. Hattaway and Jones (1983), John and David Eicher (2001), and Jennifer M. Murray (2012), state that 99 joined the Confederate army and 114 returned to the Union forces.
With the Southern slave states declaring secession from the United States, and with a shortage of soldiers in the army, President Abraham Lincoln called on the states to raise a force of 75,000 troops for three months to put down the Confederate insurrection and defend the national capital in Washington, D.C.
Lincoln's call forced the border states to choose sides, and four seceded, making the Confederacy eleven states strong. 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. That was the day that Congress initially approved and authorized subsidy to allow and support a volunteer army of up to 500,000 troops to the cause.
The call for volunteers initially was easily met by patriotic Northerners, abolitionists, and even immigrants who enlisted for a steady income and meals. Over 10,000 German Americans in New York and Pennsylvania immediately responded to Lincoln's call, along with Northern French Americans, who were also quick to volunteer. As more men were needed, however, the number of volunteers fell and both money bounties and forced conscription had to be turned to. Many Southern Unionists would also fight for the Union army. An estimated 100,000 white soldiers from states within the Confederacy served in Union army units. Between April 1861 and April 1865, at least 2,128,948 men served in the United States Army, of whom the majority were volunteers.
It is a misconception that the South held an advantage because of the large percentage of professional officers who resigned to join the Confederate army. At the start of the war, there were 824 graduates of the U.S. Military Academy on the active list; of these, 296 resigned or were dismissed, and 184 of those became Confederate officers. Of the approximately 900 West Point graduates who were then civilians, 400 returned to the U.S. Army and 99 to the Confederacy. The ratio of U.S. Army to Confederate professional officers was 642 to 283. One of the resigning officers was Robert E. Lee, who had been offered the assignment as commander of a field army to suppress the rebellion. Lee initially disapproved of secession, but refused to bear arms against his native state, Virginia, and resigned to accept the position as commander of the Virginian Confederate forces. Lee eventually became the overall commander of the Confederate army.
The Confederacy had the advantage of having several military colleges, including The Citadel and Virginia Military Institute, but they produced fewer officers. Though officers were able to resign, enlisted soldiers did not have this right. As they usually had to either desert or wait until their enlistment term was over in order to join the Confederate States Army; though few are believed to have done so, their total number is unknown.
Organization
Leadership
U.S. President Abraham Lincoln exercised supreme command and control over the army in his capacity as 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, 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:
Winfield Scott: July 5, 1841 – November 1, 1861
George B. McClellan: November 1, 1861 – March 11, 1862
Henry W. Halleck: July 23, 1862 – March 9, 1864
Ulysses S. Grant: March 9, 1864 – 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, the chairman, with Department of War bureau chiefs Lorenzo Thomas (Adjutant General), Montgomery C. Meigs (Quartermaster General), Joseph G. Totten (Chief of Engineers), James W. Ripley (Chief of Ordnance), and Joseph P. Taylor (Commissary General).
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 adjutant general, inspector general, paymaster-general, judge advocate general, chief of engineers, chief of topographical engineers, quartermaster general, commissary general of subsistence, chief of ordnance, and surgeon general.
After the war started, the position of Provost Marshal General was also created. 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. The 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 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.
Major organizations
The Union army was composed of numerous organizations, which were generally organized geographically.
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; and were modeled close to, though not synonymous with, the existing theaters of war.
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).
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. Some of the most prominent armies were:
Army of the Cumberland, the army operating primarily in Tennessee, and later 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, 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 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, commanded by George B. McClellan, Ambrose E. Burnside, Joseph Hooker, and George G. Meade.
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, 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 for the Northern Virginia Campaign.
Each of these armies was usually commanded by a 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. 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. 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. 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.
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.
Personnel
Regulars vs. volunteers
During the course of the Civil War, the vast majority of soldiers fighting to preserve the Union were in the volunteer units. The pre-war regular army numbered approximately 16,400 soldiers, but by the end while the Union army had grown to over a million soldiers, the number of regular personnel was still approximately 21,699, of whom several were serving with volunteer forces. Only 62,000 commissions and enlistments in total were issued for the regular army during the war as most new personnel preferred volunteer service. Due to their pre-war experience, they were considered by many as elite troops and during battles were often kept in reserve in case of emergencies.
Since before the Civil War, the American public had a generally negative view of the nation's armed forces, attributable to a Jeffersonian ideal which saw standing armies as a threat to democracy and instead valorized the "citizen soldier" as being more in keeping with American ideals of equality and rugged individualism. This attitude remained unchanged during the Civil War, and afterwards many would attribute the Union's victory to the volunteers rather than the leadership and staff work provided by the regular army. In return, officers of the regular army despised the militia and saw them as having dubious value. Commentators such as Emory Upton would later argue that the reliance on militia for the nation's defense was responsible for prolonging conflicts and making them more expensive in both money and lives spent.
Despite these attitudes towards the regulars, they would serve as an important foundation around which the Union army was built. In the disastrous First Battle of Bull Run, it was the regulars who acted as rearguard during the retreat while the volunteers fled, and when George McClellan was put in charge of what became the Army of the Potomac he used regular officers and non-commissioned officers to train the volunteers. Training the volunteers, especially in regards to critical administrative and logistical matters, remained an important function of the regulars during the war. This was particularly the case with regular army artillery, as they were more widely dispersed than the infantry and cavalry (making them more visible to the volunteers) and were assigned to specific units to train their volunteer counterparts.
In battle, the regulars' performance could impress even the most battle-hardened volunteers. 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. As one volunteer put it, "For two years the U.S. Regulars taught us how to be soldiers [;] in the Wheatfield at Gettysburg, they taught us how to die like soldiers." The regulars became the standard by which the Volunteers were measured, and to be described as being as good or better than them was considered the highest compliment.
Officers
Commissioned officers in the Union army could be divided in several categories: general officers, including lieutenant general, which was added on March 2, 1864, major generals and brigadier generals; field officers including colonels, lieutenant colonels and majors; and company officers including captains, first lieutenants and second lieutenants. There was further differentiation between line officers, who were members of the artillery, cavalry or infantry branches, and staff officers, who were part of the various departments and bureaus of the War Department. All line officers outranked staff officers except in cases pertaining to their staff assignment, in which they received their orders from their respective department chiefs. Regular general officers outranked volunteer general officers of the same grade regardless of their date of commission, a feature which could have become a subject of contention. The use of brevet ranks was also a common feature of the Union army.
Officer appointments depended on the commission grade and whether it was in the regular or volunteer forces. The President reserved the right to issue commission for all regular officers and for general officers in the volunteer forces. Volunteer field and company-grade officers could be commissioned by either the president or their respective governor. Company officers were also unique in that they were usually elected by members of their company. The political appointment and/or election of volunteer officers was part of a long-standing militia tradition and of a political patronage system common in the United States. While many of these officers were West Point graduates or had prior military experience, others had none, nor was military leadership a primary consideration in such appointments. Such a policy inevitably resulted in the promotion of inept officers over more able commanders. As the war dragged on and casualties mounted, governors reacted to their constituents' complaints and instead began to issue commissions on the basis of battlefield rather than political competence.
Officers tended to suffer a higher percentage of battle wounds on account of either the necessity of leading their units into combat and their conspicuousness when accompanied by staff and escorts.
Among memorable field leaders of the army were Nathaniel Lyon (first Union general to be killed in battle during the war), William Rosecrans, George Henry Thomas, William Tecumseh Sherman, Phil Sheridan, and Benjamin F. Butler.
Officer ranks
Lieutenant general: The rank of lieutenant general did not exist in the Union army for most of the war until February 1864, when an Act of Congress allowed for its creation. A single lieutenant general was authorized to serve as the commander of all the field armies and geographic departments of the United States, under the direction and at the pleasure of the President. By law, they were allowed two secretaries and four aides-de-camp with the rank of lieutenant colonel, and a chief of staff with the rank of brigadier general.