page_title: Army of the Potomac
section_title: Corps
hierarchical_section_title: Army of the Potomac / Famous units / Corps
caption_attribution_description: English: Scouts and guides of the Army of the Potomac, photograph from the book "Original Photographs Taken on the Battlefields During the Civil War," by Mathew Brady and Alexander Gardner, 1907, published by E.B. Eaton, Hartford, Connecticut. Retouched by MarmadukePercy
context_page_description: The Army of the Potomac was the principal Union Army in the Eastern Theater of the American Civil War. It was created in July 1861 shortly after the First Battle of Bull Run and was disbanded in June 1865 following the surrender of the Confederate Army of Northern Virginia in April.
context_section_description: The army originally consisted of fourteen divisions commanded by Edwin Sumner, William B. Franklin, Louis Blenker, Nathaniel Banks, Frederick W. Lander, Silas Casey, Irvin McDowell, Fitz-John Porter, Samuel Heintzelman, Erasmus Keyes, William F. Smith, Charles P. Stone (replaced by John Sedgwick in February 1862), and George McCall. Because this arrangement would be too hard to control in battle, President Lincoln issued an order on March 13, 1862, dividing the army into six corps headed by Sumner, Banks (despite being in the Shenandoah Valley and not part of the main army), McDowell, Heintzelman, and Keyes, the highest-ranking officers. McClellan was not happy with this, as he had intended to wait until the army had been tested in battle before judging which generals were suitable for corps command.
  After the Battle of Williamsburg on May 5, McClellan requested and obtained permission to create two additions corps; these became the V Corps, headed by Brig. Gen Fitz-John Porter, and the VI Corps, headed by Brig. Gen William B. Franklin, both personal favorites of his. After the Battle of Kernstown in the Valley on March 23, the administration became paranoid about "Stonewall" Jackson's activities there and the potential danger they posed to Washington D.C., and to McClellan's displeasure, detached Blenker's division from the II Corps and sent it to West Virginia to serve under John C. Fremont's command. McDowell's corps was detached as well and stationed in the Rappahannock area.
  In June 1862, George McCall's division from McDowell's corps (the Pennsylvania Reserves Division) was sent down to the Peninsula and temporarily attached to the V Corps. In the Seven Days Battles, the V Corps was heavily engaged. The Pennsylvania Reserves, in particular, suffered heavy losses including its division commander, who was captured by the Confederates, and two of its three brigadiers (John F. Reynolds, also captured, and George Meade, who was wounded). The III Corps fought at Glendale, however, the rest of the army was not heavily engaged in the week-long fight aside from Slocum's division of the VI Corps, which was sent to reinforce the V Corps at Gaines Mill.
  The Army of the Potomac remained on the Virginia Peninsula until August, when it was recalled back to Washington D.C. Keyes and one of the two IV Corps divisions were left behind permanently as part of the newly created Department of the James, while the other division, commanded by Brig. Gen Darius Couch was attached to the VI Corps.
  During the Second Battle of Bull Run, the III and V Corps were temporarily attached to Pope's army; the former suffered major losses and was sent back to Washington to rest and refit afterward, so it did not participate in the Maryland Campaign. The V Corps attracted controversy during the battle when Fitz-John Porter failed to execute Pope's orders properly and attack Stonewall Jackson's flank despite his protests that James Longstreet's troops were blocking the way. Pope blamed the loss at Second Bull Run on Porter, who was court-martialed and spent much of his life attempting to get himself exonerated. Sigel's command, now redesignated the XI Corps, also spent the Maryland Campaign in Washington resting and refitting.
  In the Maryland Campaign, the Army of the Potomac had six corps. These were the I Corps, commanded by Joe Hooker after Irvin McDowell was removed from command, the II Corps, commanded by Edwin Sumner, the V Corps, headed by Fitz-John Porter, the VI Corps, headed by William Franklin, the IX Corps, headed by Ambrose Burnside and formerly the Department of North Carolina, and the XII Corps, headed by Nathaniel Banks until September 12, and given to Joseph K. Mansfield just two days prior to Antietam, where he was killed in action.
  At Antietam, the I and XII Corps were the first Union outfits to fight and both corps suffered enormous casualties (plus the loss of their commanders) so that they were down to near-division strength and their brigades at regimental strength after the battle was over. The II and IX Corps were also heavily e
caption: Scouts and guides, Army of the Potomac, Mathew Brady
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