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.McPherson, pp.36–37. 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.Newell, p. 52. 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.Hattaway & Jones, pp. 9–10Eicher, p. 46.
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.Crofts, Daniel W. CIVIL WAR SESQUICENTENNIAL: Unionism. digitalcommons.lsu.edu. Retrieved January 29, 2021 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:United States Army Logistics, 1775–1992: An Anthology. (1997). United States: Center of Military History, U.S. Army. p. 194-195 Winfield Scott: July 5, 1841November 1, 1861 George B. McClellan: November 1, 1861March 11, 1862 Henry W. Halleck: July 23, 1862March 9, 1864 Ulysses S. Grant: March 9, 1864March 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).Eicher, pp. 37–38.
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.Eicher, p. 58 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.Eicher, p. 65-66 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.