Army of the Potomac

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 May 1865 following the surrender of the Confederate Army of Northern Virginia in April.

Army of the Potomac
Potomac Staff
Commanders of the Army of the Potomac at Culpeper, Virginia, 1863. From the left: Gouverneur K. Warren, William H. French, George G. Meade, Henry J. Hunt, Andrew A. Humphreys, George Sykes
FoundedJuly 26, 1861
DisbandedJune 28, 1865
Country United States
BranchSeal of the United States Board of War and Ordnance.svg United States Army
TypeField army
RolePrimary Union Army in Eastern Theater
Part ofUnion Army
Garrison/HQWashington, D.C.
EngagementsAmerican Civil War
George B. McClellan
Ambrose Burnside
Joseph Hooker
George G. Meade


The Army of the Potomac was created in 1861 but was then only the size of a corps (relative to the size of Union armies later in the war). Its nucleus was called the Army of Northeastern Virginia, under Brig. Gen. Irvin McDowell, and it was the army that fought (and lost) the war's first major battle, the First Battle of Bull Run. The arrival in Washington, D.C., of Maj. Gen. George B. McClellan dramatically changed the makeup of that army. McClellan's original assignment was to command the Division of the Potomac, which included the Department of Northeast Virginia under McDowell and the Department of Washington under Brig. Gen. Joseph K. Mansfield. On July 26, 1861, the Department of the Shenandoah, commanded by Maj. Gen. Nathaniel P. Banks, was merged with McClellan's departments and on that day, McClellan formed the Army of the Potomac, which was composed of all military forces in the former Departments of Northeastern Virginia, Washington, Pennsylvania, and the Shenandoah. The men under Banks's command became an infantry division in the Army of the Potomac.[1] The army started with four corps, but these were divided during the Peninsula Campaign to produce two more. After the Second Battle of Bull Run, the Army of the Potomac absorbed the units that had served under Maj. Gen. John Pope.

It is a popular, but mistaken, belief that John Pope commanded the Army of the Potomac in the summer of 1862 after McClellan's unsuccessful Peninsula Campaign. On the contrary, Pope's army consisted of different units, and was named the Army of Virginia. During the time that the Army of Virginia existed, the Army of the Potomac was headquartered on the Virginia Peninsula, and then outside Washington, D.C., with McClellan still in command, although three corps of the Army of the Potomac were sent to northern Virginia and were under Pope's operational control during the Northern Virginia Campaign.

The Army of the Potomac -- Our Outlying Picket in the Woods
The Army of the Potomac – Our Outlying Picket in the Woods, 1862

The Army of the Potomac underwent many structural changes during its existence. The army was divided by Ambrose Burnside into three grand divisions of two corps each with a Reserve composed of two more. Hooker abolished the grand divisions. Thereafter the individual corps, seven of which remained in Virginia, reported directly to army headquarters. Hooker also created a Cavalry Corps by combining units that previously had served as smaller formations. In late 1863, two corps were sent West, and— in 1864— the remaining five corps were recombined into three. Burnside's IX Corps, which accompanied the army at the start of Ulysses S. Grant's Overland Campaign, rejoined the army later. For more detail, see the section Corps below.

The Army of the Potomac fought in most of the Eastern Theater campaigns, primarily in (Eastern) Virginia, Maryland, and Pennsylvania. After the end of the war, it was disbanded on June 28, 1865, shortly following its participation in the Grand Review of the Armies.

The Army of the Potomac was also the name given to General P. G. T. Beauregard's Confederate army during the early stages of the war (namely, First Bull Run; thus, the losing Union Army ended up adopting the name of the winning Confederate army). However, the name was eventually changed to the Army of Northern Virginia, which became famous under General Robert E. Lee.

In 1869 the Society of the Army of the Potomac was formed as a veterans association. It had its last reunion in 1929.

Grand Review of the Army of the Potomac – Drawn by Mr. Thomas Nast (from Harper's Weekly) MET DP831348
Grand Review of the Army of the Potomac, drawn by Thomas Nast, Harper's Weekly, October 10, 1863

Famous units

Civil War steeplechase2
Saint Patrick's Day celebration in the Army of the Potomac, depicting a steeplechase race among the Irish Brigade, March 17, 1863, by Edwin Forbes

Because of its proximity to the large cities of the North, such as Washington, D.C., Philadelphia, and New York City, the Army of the Potomac received more contemporary media coverage than the other Union field armies. Such coverage produced fame for a number of this army's units. Individual brigades, such as the Irish Brigade, the Philadelphia Brigade, the First New Jersey Brigade, the Vermont Brigade, and the Iron Brigade, all became well known to the general public, both during the Civil War and afterward.


Scouts and guides Army of the Potomac
Scouts and guides, Army of the Potomac, Mathew Brady

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 engaged but the V and VI Corps largely stayed out of the battle.

When Burnside took over command of the army from McClellan in the fall, he formed the army into four Grand Divisions. The Right Grand Division was commanded by Edwin Sumner and comprised the II and V Corps, the Center Grand Division, commanded by Joe Hooker, comprised the IX and III Corps, and the Left Grand Division, commanded by William Franklin, comprised the VI and I Corps. In addition, the Reserve Grand Division, commanded by Franz Sigel, comprised the XI and XII Corps.

At Fredericksburg, the I Corps was commanded by John F. Reynolds, the II Corps by Darius Couch, the III Corps by George Stoneman, the V Corps by Daniel Butterfield, the VI Corps by William F. Smith, and the IX Corps by Orlando Willcox. The XI Corps was commanded by Franz Sigel and the XII Corps by Henry Slocum, however, neither corps was present at Fredericksburg, the former not arriving until after the battle was over, and the latter was stationed at Harper's Ferry.

Following Fredericksburg, Burnside was removed from command of the army and replaced by Joe Hooker. Hooker immediately abolished the Grand Divisions and also for the first time organized the cavalry into a proper corps led by George Stoneman instead of having them ineffectually scattered among infantry divisions. Burnside and his old IX Corps departed out to a command in the Western Theater. The I, II, and XII Corps retained the same commanders they had had during the Fredericksburg campaign, but the other corps got new commanders once again. Daniel Butterfield was chosen by Hooker as his new chief of staff and command of the V Corps went to George Meade. Daniel Sickles received command of the III Corps and Oliver Howard the XI Corps after Franz Sigel had resigned, refusing to serve under Hooker, his junior in rank. William Franklin also left the army for the same reason. Edwin Sumner, who was in his 60s and exhausted from campaigning, departed as well and died a few months later. William F. Smith resigned from command of the VI Corps, which was taken over by John Sedgwick. The I and V Corps were not significantly engaged during the Chancellorsville campaign.

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.

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.

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.[2] 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.

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.[3] 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.[4]


  • Brigadier General Irvin McDowell: Commander of the Army and Department of Northeastern Virginia (May 27 – July 25, 1861)
  • Major General George B. McClellan: Commander of the Military Division of the Potomac, and later, the Army and Department of the Potomac (July 26, 1861 – November 9, 1862)
  • Major General Ambrose E. Burnside: Commander of the Army of the Potomac (November 9, 1862 – January 26, 1863)
  • Major General Joseph Hooker: Commander of the Army and Department of the Potomac (January 26 – June 28, 1863)
  • Major General George G. Meade: Commander of the Army of the Potomac† (June 28, 1863 – June 28, 1865)

†Major General John G. Parke took brief temporary command during Meade's absences on four occasions during this period)

Lt. Gen. Ulysses S. Grant, general-in-chief of all Union armies, located his headquarters with the Army of the Potomac and provided operational direction to Meade from May 1864 to April 1865, but Meade retained command of the Army of the Potomac.

Major battles and campaigns

Casualties breakdown

Below is the grand recapitulation of the losses sustained by the Army of the Potomac and the Army of the James, from May 5, 1864 to April 9, 1865, compiled in the Adjutant-General's Office, Washington:

Military history of Ulysses S. Grant, from April, 1861, to April, 1865 (1885) (14576021360)


  1. ^ Beatie, p. 480.
  2. ^ Welcher, pp. 361–62.
  3. ^ Welcher, pp. 428, 431.
  4. ^ Welcher, pp. 536, 540.


  • Beatie, Russel H. Army of the Potomac: Birth of Command, November 1860 – September 1861. New York: Da Capo Press, 2002. ISBN 0-306-81141-3.
  • Beatie, Russel H. Army of the Potomac: McClellan Takes Command, September 1861 – February 1862. New York: Da Capo Press, 2004. ISBN 0-306-81252-5.
  • Beatie, Russel H. Army of the Potomac: McClellan's First Campaign, March – May 1862. New York: Savas Beatie, 2007. ISBN 978-1-932714-25-8.
  • Eicher, John H., and Eicher, David J., Civil War High Commands, Stanford University Press, 2001, ISBN 0-8047-3641-3.
  • Welcher, Frank J. The Union Army, 1861–1865 Organization and Operations. Vol. 1, The Eastern Theater. Bloomington: Indiana University Press, 1989. ISBN 0-253-36453-1.

Further reading

  • Chamberlain, Joshua L. The Passing of the Armies: An Account of the Final Campaign of the Army of the Potomac. New York: Bantam Books, 1993. ISBN 0-553-29992-1. First published in 1915 by G.P. Putnam's Sons.
  • Sears, Stephen W. Lincoln's Lieutenants: The High Command of the Army of the Potomac (Boston: Houghton Mifflin Harcourt, 2017), xii, 884 pp.
  • Taaffe, Stephen R. Commanding the Army of the Potomac. Lawrence: University of Kansas Press, 2006. ISBN 0-7006-1451-6.

External links

Alfred Pleasonton

Alfred Pleasonton (July 7, 1824 – February 17, 1897) was a United States Army officer and major general of volunteers in the Union cavalry during the American Civil War. He commanded the Cavalry Corps of the Army of the Potomac during the Gettysburg Campaign, including the largest predominantly cavalry battle of the war, Brandy Station. In 1864, he was transferred to the Trans-Mississippi Theater, where he defeated Confederate General Sterling Price in two key battles, including the Battle of Mine Creek, the second largest cavalry battle of the war, effectively ending the war in Missouri. He was the son of Stephen Pleasonton and younger brother of Augustus Pleasonton.

American Civil War Corps Badges

Corps badges in the American Civil War were originally worn by soldiers of the Union Army on the top of their army forage cap (kepi), left side of the hat, or over their left breast. The idea is attributed to Maj. Gen. Philip Kearny, who ordered the men in his division to sew a two-inch square of red cloth on their hats to avoid confusion on the battlefield. This idea was adopted by Maj. Gen. Joseph Hooker after he assumed command of the Army of the Potomac, so any soldier could be identified at a distance.

Maj. Gen. Daniel Butterfield, Hooker's chief of staff, was assigned the task of designing a distinctive shape for each corps badge. Butterfield also designated that each division in the corps should have a variation of the corps badge in a different color. Division badges were colored as follows:

Red — First division of corps

White — Second division of corps

Blue — Third division of corpsThese were used in the United States' Army of the Potomac. For the most part, these rules were adopted by other Union Armies, however it was not universal. For example, the XIII Corps never adopted a badge, and the XIX Corps had the first division wear a red badge, the second division wear a blue badge, and the third division wear white.

For Army corps that had more than three divisions, the standardization was lost:

Green — Fourth division of VI, IX, and XX Corps

Yellow — Fourth division of XV Corps (reportedly Orange was also used for a 5th Division Badge)

Multicolor — Headquarters or artillery elements (certain corps)The badges for enlisted men were cut from colored cloth, while officer's badges were privately made and of a higher quality. Metallic badges were often made by jewelers and were personalized for the user. The badges eventually became part of the Army regulations and a great source of regimental pride.

Army of Northern Virginia

The Army of Northern Virginia was the primary military force of the Confederate States of America in the Eastern Theater of the American Civil War. It was also the primary command structure of the Department of Northern Virginia. It was most often arrayed against the Union Army of the Potomac.

Army of Virginia

The Army of Virginia was organized as a major unit of the Union Army and operated briefly and unsuccessfully in 1862 in the American Civil War. It should not be confused with its principal opponent, the Confederate Army of Northern Virginia, commanded by Robert E. Lee.

Cavalry Corps (Union Army)

Two corps of the Union Army were called Cavalry Corps during the American Civil War. One served with the Army of the Potomac; the other served in the various armies of the western theater of the war.

Confederate Army of the Potomac

The Confederate Army of the Potomac, whose name was short-lived, was the command under Brig. Gen. P. G. T. Beauregard in the early days of the American Civil War. Its only major combat action was the First Battle of Bull Run. Afterwards, the Army of the Shenandoah was merged into the Army of the Potomac with Gen. Joseph E. Johnston, the commander of the Shenandoah, taking command. The Army of the Potomac was renamed the Army of Northern Virginia on March 14, 1862, with Beauregard's original army eventually becoming the First Corps, Army of Northern Virginia.

Eastern Theater of the American Civil War

The Eastern Theater of the American Civil War consists of the major military and naval operations in the states of Virginia, West Virginia, Maryland, and Pennsylvania, the District of Columbia, and the coastal fortifications and seaports of North Carolina. (Operations in the interior of the Carolinas in 1865 are considered part of the Western Theater, while the other coastal areas along the Atlantic Ocean are included in the Lower Seaboard Theater.)

The Eastern Theater was the venue for several major campaigns launched by the Union Army of the Potomac to capture the Confederate capital of Richmond, Virginia; many of these were frustrated by the Confederate Army of Northern Virginia, commanded by General Robert E. Lee. President Abraham Lincoln sought a general to match Lee's boldness, appointing in turn Maj. Gens. Irvin McDowell, George B. McClellan, John Pope, Ambrose Burnside, Joseph Hooker, and George G. Meade to command his principal Eastern armies. While Meade gained a decisive victory over Lee at the Battle of Gettysburg in July 1863, it was not until newly appointed general-in-chief Ulysses S. Grant arrived from the Western Theater in 1864 to take personal control of operations in Virginia that Union forces were able to capture Richmond, but only after several bloody battles of the Overland Campaign and a nine-month siege near the cities of Petersburg and Richmond. The surrender of Lee's army at Appomattox Court House in April 1865 brought major operations in the area to a close.

While many of the campaigns and battles were fought in the region of Virginia between Washington, D.C., and Richmond, there were other major campaigns fought nearby. The Western Virginia Campaign of 1861 secured Union control over the western counties of Virginia, which would be formed into the new state of West Virginia. Confederate coastal areas and ports were seized in southeastern Virginia and North Carolina. The Shenandoah Valley was marked by frequent clashes in 1862, 1863, and 1864. Lee launched two unsuccessful invasions of Union territory in hopes of influencing Northern opinion to end the war. In the fall of 1862, Lee followed his successful Northern Virginia Campaign with his first invasion, the Maryland Campaign, which culminated in his strategic defeat in the Battle of Antietam. In the summer of 1863, Lee's second invasion, the Gettysburg Campaign, reached into Pennsylvania, farther north than any other major Confederate army. Following a Confederate attack on Washington, D.C., itself in 1864, Union forces commanded by Philip H. Sheridan launched a campaign in the Shenandoah Valley, which cost the Confederacy control over a major food supply for Lee's army.

George B. McClellan

George Brinton McClellan (December 3, 1826 – October 29, 1885) was an American soldier, civil engineer, railroad executive, and politician. A graduate of West Point, McClellan served with distinction during the Mexican War (1846–1848), and later left the Army to work in railroads until the outbreak of the Civil War (1861–1865). Early in the war, McClellan was appointed to the rank of major general and played an important role in raising a well-trained and organized army, which would become the Army of the Potomac in the Eastern Theater; he served a brief period (November 1861 to March 1862) as general-in-chief of the Union Army. Although McClellan was meticulous in his planning and preparations, these very characteristics hampered his ability to challenge aggressive opponents in a fast-moving battlefield environment. He chronically overestimated the strength of enemy units and was reluctant to apply principles of mass, frequently leaving large portions of his army unengaged at decisive points.

McClellan organized and led the Union army in the Peninsula Campaign in southeastern Virginia from March through July 1862. It was the first large-scale offensive in the Eastern Theater. Making an amphibious clockwise turning movement around the Confederate Army in northern Virginia, McClellan's forces turned west to move up the Virginia Peninsula, between the James and York Rivers landing from the Chesapeake Bay, with the Confederate capital, Richmond, as their objective. Initially, McClellan was somewhat successful against the equally cautious General Joseph E. Johnston, but the military emergence of General Robert E. Lee to command the Army of Northern Virginia turned the subsequent Seven Days Battles into a partial Union defeat.

General McClellan failed to maintain the trust of President Abraham Lincoln. He did not trust his commander-in-chief and was privately derisive of him. He was removed from command in November after failing to decisively pursue Lee's Army following the tactically inconclusive but strategic Union victory at the Battle of Antietam outside Sharpsburg, Maryland, and never received another field command. McClellan went on to become the unsuccessful Democratic Party nominee in the 1864 presidential election against Lincoln's reelection. The effectiveness of his campaign was damaged when he repudiated his party's platform, which promised an end to the war and negotiations with the southern Confederacy. He served as the 24th Governor of New Jersey from 1878 to 1881, and eventually became a writer, and vigorously defended his Civil War conduct.

Most modern authorities have assessed McClellan as a poor battlefield general. Some historians view him as a highly capable commander whose reputation suffered unfairly at the hands of pro-Lincoln partisans who made him a scapegoat for the Union's military setbacks. After the war, subsequent commanding general and 18th President Ulysses S. Grant was asked for his opinion of McClellan as a general; he replied, "McClellan is to me one of the mysteries of the war."

George Meade

George Gordon Meade (December 31, 1815 – November 6, 1872) was a career United States Army officer and civil engineer best known for defeating Confederate General Robert E. Lee at the Battle of Gettysburg in the American Civil War. He previously fought with distinction in the Second Seminole War and the Mexican–American War. During the Civil War, he served as a Union general, rising from command of a brigade to command of the Army of the Potomac. Earlier in his career, he was an engineer and was involved in the coastal construction of several lighthouses.

Meade's Civil War combat experience started as a brigade commander in the Peninsula Campaign and the Seven Days Battles. He was severely wounded while leading his brigade at the Battle of Glendale. As a division commander, he had notable success at the Battle of South Mountain and assumed temporary corps command at the Battle of Antietam. Meade's division was arguably the most successful of any at the Battle of Fredericksburg in December. It was part of a force charged with driving the Confederate troops under Stonewall Jackson back from their position on Prospect Hill. The division made it further than any other, but was forced to turn back due to a lack of reinforcements. Meade was promoted to commander of the V Corps, which he led during the Battle of Chancellorsville.

During the Gettysburg Campaign, he was appointed to command the Army of the Potomac just three days before the Battle of Gettysburg. Arriving on the field after the first day's action on July 1, Meade organized his army on favorable ground to fight an effective defensive battle against Robert E. Lee's Army of Northern Virginia, repelling a series of massive assaults throughout the next two days. Lee was forced to retreat to Virginia, ending his hope of winning the war through a successful invasion of the North. This victory was marred by Meade's ineffective pursuit during the retreat, allowing Lee and his army to escape instead of completely destroying them. The Union Army also failed to follow up on its success during the Bristoe Campaign and Battle of Mine Run that fall, which ended inconclusively. Meade suffered from intense political rivalries within the Army, notably with Daniel Sickles, who tried to discredit his role in the victory at Gettysburg.

In 1864–65, Meade continued to command the Army of the Potomac through the Overland Campaign, the Richmond-Petersburg Campaign, and the Appomattox Campaign, but he was overshadowed by the direct supervision of the general-in-chief, Lt. Gen. Ulysses S. Grant, who accompanied him throughout these campaigns. Grant conducted most of the strategy during these campaigns, leaving Meade with significantly less influence than before. His image was harmed by his notoriously short temper and disdain for the press. After the war, he commanded several important departments during Reconstruction.

III Corps (Union Army)

There were four formations in the Union Army designated as III Corps (or Third Army Corps) during the American Civil War.

Three were short-lived:

In the Army of Virginia, a temporary designation of the command better known as I Corps (Army of the Potomac)::

Irvin McDowell (June 26, 1862 – September 5, 1862);

James B. Ricketts (September 5, 1862 – September 6, 1862);

Joseph Hooker (September 6, 1862 – September 12, 1862)

In the Army of the Ohio:

Charles C. Gilbert (September 29, 1862 – October 24, 1862)

In the Army of the Cumberland:

Charles C. Gilbert (October 24, 1862 – November 5, 1862)The other, the III Corps, Army of the Potomac (March 13, 1862 – March 24, 1864), is the subject of this article.

II Corps (Union Army)

There were five corps in the Union Army designated as II Corps (Second Army Corps) during the American Civil War. These formations were the Army of the Cumberland II Corps commanded by Thomas L. Crittenden from October 24, 1862, to November 5, 1862, later renumbered XXI Corps; the Army of the Mississippi II corps led by William T. Sherman from January 4, 1863, to January 12, 1863, renumbered XV Corps; Army of the Ohio II Corps commanded by Thomas L. Crittenden from September 29, 1862, to October 24, 1862, transferred to Army of the Cumberland; Army of Virginia II Corps led by Nathaniel P. Banks from June 26, 1862, to September 4, 1862, and Alpheus S. Williams from September 4, 1862, to September 12, 1862, renumbered XII Corps; and the Army of the Potomac II Corps from March 13, 1862, to June 28, 1865.

Of these five, the one most widely known was the Army of the Potomac formation, the subject of this article.

IV Corps (Union Army)

There were two corps of the Union Army called IV Corps during the American Civil War. They were separate units, one serving with the Army of the Potomac and the Department of Virginia in the Eastern Theater, 1862–1863, the other with the Army of the Cumberland in the Western Theater, 1863–1865.

IX Corps (Union Army)

IX Corps (Ninth Army Corps) was a corps of the Union Army during the American Civil War that distinguished itself in combat in multiple theaters: the Carolinas, Virginia, Kentucky, Tennessee, and Mississippi.

I Corps (Union Army)

I Corps (First Corps) was the designation of three different corps-sized units in the Union Army during the American Civil War. Separate formation called the I Corps served in the Army of the Ohio/Army of the Cumberland under Alexander M. McCook from September 29, 1862 to November 5, 1862, in the Army of the Mississippi under George W. Morgan from January 4, 1863 to January 12, 1863 (which was the re-designated XIII Corps (ACW)), and in the Army of the Potomac and Army of Virginia (see below). The first two were units of very limited life; the third was one of the most distinguished and veteran corps in the entire Union Army, commanded by very distinguished officers. The term "First Corps" is also used to describe the First Veteran Corps from 1864 to 1866.

Irvin McDowell

Irvin McDowell (October 15, 1818 – May 4, 1885) was a career American army officer. He is best known for his defeat in the First Battle of Bull Run, the first large-scale battle of the American Civil War. In 1862, he was given command of the I Corps of the Army of the Potomac. He fought unsuccessfully against Stonewall Jackson's troops during the Valley Campaign of 1862, and was blamed for contributing to the defeat of United States troops at the Second Battle of Bull Run in August.

John F. Reynolds

John Fulton Reynolds (September 20, 1820 – July 1, 1863) was a career United States Army officer and a general in the American Civil War. One of the Union Army's most respected senior commanders, he played a key role in committing the Army of the Potomac to the Battle of Gettysburg and was killed at the start of the battle.

Joseph Hooker

Joseph Hooker (November 13, 1814 – October 31, 1879) was a career United States Army officer, achieving the rank of major general in the Union Army during the American Civil War. Although he served throughout the war, usually with distinction, Hooker is best remembered for his stunning defeat by Confederate General Robert E. Lee at the Battle of Chancellorsville in 1863.

After graduating from the United States Military Academy in 1837, Hooker served in the Seminole Wars and the Mexican–American War, receiving three brevet promotions. He resigned from the Army in 1853 and pursued farming, land development, and (unsuccessfully) politics in California. After the start of the Civil War he returned to the Army as a brigadier general. He distinguished himself as an aggressive combat commander leading a division in the Battle of Williamsburg, May 5, 1862, resulting in his promotion to major general. As a corps commander, he led the initial Union attacks at the Battle of Antietam, in which he was wounded. At the Battle of Fredericksburg, he commanded a "Grand Division" of two corps, and was ordered to conduct numerous futile frontal assaults that caused his men to suffer serious losses. Throughout this period, he conspired against and openly criticized his army commanders. Following the defeat at Fredericksburg, he was given command of the Army of the Potomac.

Hooker planned an audacious campaign against Robert E. Lee, but his Army was defeated by the Confederate Army at the Battle of Chancellorsville. Hooker's subordinate general's mistakes, and a loss of confidence on his part contributed to a failure to marshal the strength of his larger army against Lee, who boldly divided his army and routed a Union corps with a flank attack led by Stonewall Jackson. Casualties were heavy on both sides (approximately 17,000 of the Union's 117,000 troops, and 13,000 of the Confederate's 60,000 troops), and the defeat handed Lee the initiative, which allowed him to travel north to Gettysburg.Lincoln kept Hooker in command, but when General Halleck and Lincoln declined Hooker's request for troops from Harpers Ferry to reinforce his army while in pursuit of Lee's advance toward Pennsylvania, Hooker resigned his command. George G. Meade was appointed to the command of the Army of the Potomac on June 28, 1863, three days before Gettysburg, and was allowed to take the troops from Harpers Ferry.Hooker returned to combat in November, leading two corps from the Army of the Potomac to help relieve the besieged Union Army at Chattanooga, Tennessee, and achieving an important victory at the Battle of Lookout Mountain during the Chattanooga Campaign. He continued in the Western Theater under Maj. Gen. William T. Sherman, but departed in protest before the end of the Atlanta Campaign when he was passed over for promotion to command the Army of the Tennessee.

Hooker became known as "Fighting Joe" following a journalist's clerical error reporting from the Battle of Williamsburg; however, the nickname stuck. His personal reputation was as a hard-drinking ladies' man, and his headquarters were known for parties and gambling, although the historical evidence discounts any heavy drinking by the general himself.

V Corps (Union Army)

The V Corps (Fifth Corps) was a unit of the Union Army of the Potomac during the American Civil War.

XXII Corps (Union Army)

XXII Corps was a corps in the Union Army during the American Civil War. It was created on February 2, 1863, to consist of all troops garrisoned in Washington, D.C., and included three infantry divisions and one of cavalry (under Judson Kilpatrick, which left to join the Army of the Potomac during the Gettysburg Campaign). Many of its units were transferred to the Army of the Potomac during Grant's Overland Campaign.This Corps did not include the many regiments that passed through Washington, D.C. on the way to the front or away from it. Nor does it include the many regiments from the Army of the Potomac, Army of Georgia, and Army of the Tennessee that encamped in the area to participate in the Grand Review of the Armies.

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