<P> During the Gettysburg Campaign, the army's existing organization was largely retained, but a number of brigades composed of short - term nine - month regiments departed as their enlistment terms expired . Darius Couch resigned from command of the II Corps after Chancellorsville, the corps going to Winfield Hancock . The Pennsylvania Reserves Division, having spent several months in Washington D.C. resting and refitting from the 1862 campaigns, returned to the army, but was added to the V Corps rather than rejoining the I Corps . George Stoneman had been removed from command of the cavalry corps by Hooker after a poor performance during the Chancellorsville campaign and replaced by Alfred Pleasanton . </P> <P> George Meade was suddenly appointed the commander of the army on June 28, a mere three days before the battle of Gettysburg . At the battle, the I, II, and III Corps suffered such severe losses that they were almost nonfunctional as fighting units at the end . One corps commander (Reynolds) was killed, another (Sickles) lost a leg and was permanently out of the war, and a third (Hancock) was badly wounded and never completely recovered from his injuries . The VI Corps had not been significantly engaged and was mostly used to plug up holes in the line during the battle . </P> <P> For the remainder of the war, corps were added and subtracted from the army . IV Corps was broken up after the Peninsula Campaign, with its headquarters and 2nd Division left behind in Yorktown, while its 1st Division moved north, attached to the VI Corps, in the Maryland Campaign . Those parts of the IV Corps that remained on the Peninsula were reassigned to the Department of Virginia and disbanded on October 1, 1863 . Those added to the Army of the Potomac were IX Corps, XI Corps (Sigel's I Corps in the former Army of Virginia), XII Corps (Banks's II Corps from the Army of Virginia), added in 1862; and the Cavalry Corps, created in 1863 . Eight of these corps (seven infantry, one cavalry) served in the army during 1863, but due to attrition and transfers, the army was reorganized in March 1864 with only four corps: II, V, VI, and Cavalry . Of the original eight, I and III Corps were disbanded due to heavy casualties and their units combined into other corps . The XI and XII Corps were ordered to the West in late 1863 to support the Chattanooga Campaign, and while there were combined into the XX Corps, never returning to the East . </P> <P> The IX Corps returned to the army in 1864, after being assigned to the West in 1863 and then served alongside, but not as part of, the Army of the Potomac from March to May 24, 1864 . On that latter date, IX Corps was formally added to the Army of the Potomac . Two divisions of the Cavalry Corps have transferred in August 1864 to Maj. Gen. Philip Sheridan's Army of the Shenandoah, and the 2nd Division alone remained under Meade's command . On March 26, 1865, that division was also assigned to Sheridan for the closing campaigns of the war . </P>

Battle flag of the army of the potomac