Army of the Potomac (USA)


The Army of the Potomac was the Union's primary fighting force in the Eastern Theater throughout most of the American Civil War.

George B. McClellan, General, USA, Civil War, LOC

On July 25, 1862, U.S. War Department merged the Department of Northeastern Virginia with the Department of Washington to create the Division of the Potomac, commanded by Major General George B. McClellan. McClellan commanded the Division of the Potomac and the Army of the Potomac from July 26, 1861, to November 9, 1862. Image Source: Wikimedia Commons.

The Army of the Potomac, Origin and Early History

At 4:30 a.m., April 12, 1861, Confederate forces began shelling the Federal garrison at Fort Sumter, South Carolina, plunging the United States into the American Civil War. Three days later President Abraham Lincoln issued a proclamation calling for 75,000 volunteers to suppress the Southern rebellion. On April 25, the first of what would eventually amount to thousands of raw recruits began streaming into Washington, DC. The rapid buildup of local regiments quickly required the United States War Department to create structure out of chaos. By late April, the War Department began organizing the volunteer army into military districts.

On May 27, 1861, the War Department created the Department of Northeastern Virginia, comprising part of Virginia east of the Allegheny Mountains and north of the James River, except for an area sixty miles around Fort Monroe. The War Department named Brigadier-General Irvin McDowell to command the new department. Believing that Union forces could easily capture the Confederate capital of Richmond, Virginia, President Lincoln and other high-ranking Federal officials urged McDowell to launch an offensive and to bring the rebellion to a swift end. Sensing that his troops were not yet ready for combat, McDowell reluctantly relented to political pressure and marched his soldiers out of Washington, toward Manassas, Virginia, on July 16. On July 21, 1861, the Confederate Army of the Potomac, reinforced by the Army of the Shenandoah, routed McDowell’s soldiers at the First Battle of Bull Run, sending the Northerners scurrying back to their defenses near Washington in a disorganized retreat.

One week after the embarrassing defeat, the federal government began reorganizing its forces near the nation’s capital. On July 25, 1861, the War Department issued General Orders, No. 47, merging the Department of Northeastern Virginia with the Department of Washington to create the Division of the Potomac commanded by Major General George B. McClellan. Three weeks later, on August 17, Lieutenant General Winfield Scott issued General Orders, No.15 (Headquarters of the Army) announcing a further consolidation and the creation of the Department of the Potomac, again commanded by. McClellan. On August 20, McClellan issued General Orders No. 1 (Army of the Potomac), assuming “command of the Army of the Potomac, comprising the troops serving in the former departments of Washington and Northeastern Virginia, in the Valley of the Shenandoah, and in the States of Maryland and Delaware.”

When it came to structuring his new army, however, McClellan did not have free rein. President Lincoln had his own designs. On March 8, 1862, Lincoln issued War Order No. 2, merging McClellan’s fifteen divisions into five corps. The President named Major General Irvin McDowell, Brigadier General Edwin V. Sumner, Brigadier General Samuel P. Heintzelman, Brigadier General Erasmus. D. Keyes, and Major General Nathaniel P. Banks to command the five corps, respectively.

On March 13, 1862, an irritated but compliant McClellan issued General Order No. 101 (Army of the Potomac) adopting the President’s organizational scheme and confirming Lincoln’s selections for corps commanders.

Like McDowell, McClellan well knew that his army consisted primarily of untrained volunteers. Despite considerable pressure from President Lincoln and other important Federal officials to move against the Confederacy and end the war quickly, McClellan took his time molding the Army of the Potomac into a disciplined fighting force.

Army of the Potomac Civil War Operations

Peninsula Campaign

In March 1862, after nearly nine months of preparation, McClellan transported the Army of the Potomac by ship to Fort Monroe in Virginia. With most Rebel forces encamped near Manassas, McClellan planned to march his army up the Virginia Peninsula and capture the Confederate capital at Richmond. Although he enjoyed a numerical advantage of nearly three-to-one, McClellan advanced cautiously towards Richmond. McClellan’s sluggishness provided General Joseph Johnston with ample time to reinforce the Rebel troops at Richmond. Still, the Army of the Potomac fought its way up the Peninsula to within sight of Richmond. The campaign stalled, however, when General Robert E. Lee assumed command of the forces guarding Richmond after Johnston sustained serious injuries at the Battle of Seven Pines (May 31–June 1, 1862). Lee went on the offensive, launching a series of engagements known as the Seven Days Battles that eventually drove the Army of the Potomac back to the sea, bringing to an end McClellan’s unsuccessful Peninsula Campaign.

Northern Virginia Campaign

After the Army of the Potomac retreated down the Virginia Peninsula, President Lincoln and General-in-Chief-of-the-Army, Henry Halleck, recalled it to the Washington area on August 3, 1862. With McClellan off of the peninsula, Lee turned his attention to Union Major General John Pope and his Army of Virginia and scored a major victory at the Second Battle of Bull Run (August 28–30, 1862). Reinforcements from the Army of the Potomac prevented the Union defeat from being worse than it could have been when Pope’s army retreated. Lee’s victory opened the way for a Confederate invasion of the North.

Maryland Campaign and the Battle of Antietam

After his victory at the Second Battle of Bull Run, Robert E. Lee marched the Army of Northern Virginia into Maryland. On September 4, Lee’s soldiers began crossing the Potomac River near Poolesville, Maryland. Assuming that the Federal forces near Washington were still in disarray following their stinging defeat at Bull Run, Lee believed that it was safe to divide his army temporarily.

The pivotal engagement of the Maryland Campaign occurred near Sharpsburg, Maryland along Antietam Creek. On September 17, 1862, McClellan attacked Lee. During the day, Lee’s divided army reunited on the battlefield and fought the Army of the Potomac to a standoff.

The Battle of Antietam ended as a tactical draw, but it was a strategic Union victory because McClellan halted Lee’s northern advance. The engagement was the bloodiest single day of combat during the American Civil War. The Army of the Potomac suffered 12,401 reported casualties, including 2,108 killed. Lee’s Army of Northern Virginia suffered 10,316 casualties, including 1,546 killed. Following a day of truce, during which both sides recovered and exchanged their wounded and dead, Lee began withdrawing his army back across the Potomac River, but McClellan did not press the issue.

Fredericksburg Campaign

Although the Army of the Potomac halted Robert E. Lee’s advance into Maryland, McClellan’s reluctance to press Lee’s retreating army disappointed  President Lincoln. On November 5, 1862, Lincoln issued an executive removing McClellan from command of the Army of the Potomac, replacing him with General Ambrose E. Burnside. Lincoln and General-in-Chief Henry Halleck urged Burnside to launch an invasion of Virginia quickly.

Burnside submitted a proposal to Halleck on November 9. Burnside’s plan called for the Army of the Potomac to cross the Rappahannock River at the town of Fredericksburg, to gain control of the Richmond, Fredericksburg and Potomac Railroad, and then to use the railroad for a rapid invasion of Richmond. Halleck and the President approved the proposal. On November 14, Burnside issued General Order No. 184 (Army of the Potomac), dividing the Army of the Potomac into three “grand divisions.” By November 19, 1862, Burnside arranged all three grand divisions to cross the Rappahannock.

Unfortunately for Burnside, the pontoon bridges that he planned to use to move his army across the river did not arrive until November 25. By then, Burnside’s intentions were clear to Lee, who used the delay to fortify the area around Fredericksburg. Unable to find a suitable alternative site to cross the Rappahannock and feeling pressured by Lincoln and Halleck, Burnside continued the operation and assaulted Lee’s entrenched army.

On December 13, Burnside began his attack on Lee’s army. Troops under the command of Major General William B. Franklin opened the battle by attacking the Confederate right flank. They experienced some brief success when Major General George Meade’s division penetrated the Confederate line of Lieutenant General Thomas J. “Stonewall” Jackson, but Jackson’s men drove Meade back with a counterattack.

Burnside next tried attacking Lee’s left flank, commanded by Lieutenant General James Longstreet. The ill-fated Federals had to cross a drainage ditch and an open field under a murderous fire from the well-positioned Rebels at the base of Marye’s Heights above Fredericksburg. Sixteen separate Federal charges resulted in a bloodbath. Mercifully, darkness put an end to the killing.

Determined to win the battle, Burnside planned another assault for the morning but his junior officers dissuaded him during the night. Instead, Lee granted Burnside a truce to care for the Union wounded and dead on December 14. The following day, Burnside and his defeated army limped back across the river and the Fredericksburg Campaign ended.

In the Battle’s aftermath, President Lincoln came under extreme criticism in the North. Following a second failed offensive, derisively known as the Mud March, in January 1863, Burnside was facing severe criticism from several of his subordinate officers. As accusations intensified, Burnside requested an audience with President Lincoln on January 23, 1863. During the meeting, Burnside presented General Orders No. 8 (Army of the Potomac), which proposed dismissing Major General Joseph Hooker from the army (on approval of the President), and also proposed relieving many of Burnside’s subordinate general officers of their command. The besieged general demanded that Lincoln either approve the order or accept Burnside’s resignation. Unwilling to authorize a wholesale dismissal of his generals, Lincoln instead drafted General Orders No. 20 (U.S. War Department) on January 25, 1863, announcing that Burnside was being relieved of command of the Army of the Potomac, at his own request. The order named Major General Joseph Hooker as Burnside’s successor.

Chancellorsville Campaign

When Hooker assumed command of the Army of the Potomac, morale was sinking, and desertions were rising. Hooker spent his first few months in charge of the army implementing reforms that raised the spirits of his soldiers. On February 5, 1863, Hooker issued General Orders, No. 6 (Army of the Potomac), discontinuing Burnside’s Grand Divisions and naming eight corps commanders. By spring, the army was ready for another offensive. Hooker’s first test as commander of the army came at the Battle of Chancellorsville (April 30–May 6, 1863), where he proved no match for Robert E. Lee. Despite being outnumbered nearly two to one, Lee out-maneuvered the Federal army and drove the Northerners from the field.

The Confederate victory at Chancellorsville prompted Robert E. Lee to launch a second invasion of the North in June 1863. As Lee moved north, President Lincoln ordered Hooker to move in a parallel direction, keeping the Army of the Potomac between Lee and the nation’s capital. On June 27, 1863, Hooker attended a strategy meeting with the President and General-in-chief Henry W. Halleck. When a dispute arose regarding the disposition of troops at Harpers Ferry, Hooker impulsively offered to resign his command. Lincoln quickly accepted the resignation and had Secretary of War Edwin M. Stanton issue General Orders, No. 194 (U.S. War Department) placing George Meade in command of the Army of the Potomac just four days before the pivotal Battle of Gettysburg.

Gettysburg Campaign

Upon assuming his new command, Meade quickly began moving north from Frederick, Maryland in search of Lee’s army in Pennsylvania. When Lee learned of Meade’s aggressive pursuit, he ordered his scattered army to gather at Cashtown, approximately eight miles west of the village of Gettysburg, Pennsylvania.

On June 30, 1863, Union cavalry commanded by Brigadier-General John Buford entered Gettysburg from the south. Recognizing the strategic importance of the high ground near Gettysburg, Buford ordered his troopers to dismount and hold the town until reinforcements arrived. The next morning, Confederate General A. P. Hill sent two brigades into Gettysburg and launched an assault on the Federal cavalry, despite Lee’s orders to avoid a general engagement until he could reunite the Army of Northern Virginia.

Notwithstanding Lee’s wishes, the battle grew in size and intensity. What began as an accidental encounter on July 1 evolved into a full-scale showdown during the next two days. When the fighting ended, sites such as Cemetery Hill, Little Round Top, Devil’s Den, the Wheatfield, the Peach Orchard, and Cemetery Ridge were indelibly etched in the annals of American history. Intense combat between the two armies produced between 45,000 and 51,000 casualties, including nearly 8,000 dead, making Gettysburg the bloodiest battle of the Civil War. When the fighting ended on July 3, the Army of the Potomac prevailed.

Following the Union victory at Gettysburg, Lee ended his second invasion of the North and withdrew toward Virginia. Despite prodding from his superiors in Washington to pursue the Confederate army, Meade settled for dispatching his cavalry to harass the retreating Confederates. Meade had reason to be cautious. The previous three days of battle had tired and battered the Army of the Potomac. By the time Meade started a more aggressive pursuit, Lee crossed the Potomac River, bringing an end to the Gettysburg Campaign.

Bristoe Campaign

In September, Confederate officials pressured Lee into sending Lieutenant General James Longstreet’s 1st Corps to Chattanooga where Major General William Rosecrans and the Union Army of the Cumberland were battering Lieutenant General Braxton Bragg and the Confederate Army of Tennessee. When Meade learned that Lee had weakened his army, he renewed his pursuit. In mid-September, Meade sent two columns forward to engage the remnants of Lee’s army, encamped along the Rapidan River.

The tables quickly turned, however, when Washington officials ordered Meade’s 11th and 12th Corps to Tennessee, under the command of Joseph Hooker, to support the Army of the Cumberland, which was under siege at Chattanooga following the Confederate victory at the Battle of Chickamauga (September 19–20, 1863). Hooker’s troops performed well at the Battle of Lookout Mountain (November 24, 1863) and the Battle of Chattanooga (November 23–25, 1863).

Back in Virginia, with the size of Meade’s army also depleted, Lee responded by crossing the Rappahannock River and launching an offensive aimed at Meade’s right flank. Meade countered by beginning a withdrawal to secure his supply depot at Centerville.

On October 13, Confederate Major General J. E. B. Stuart and his cavalry skirmished with the rearguard of the Union 3rd Corps near Auburn, in Fauquier County, Virginia. On the next day, Major General Gouverneur Warren and the Union 2nd Corps caught elements of Confederate General A. P. Hill’s corps in a deadly ambush at the Battle of Bristoe Station (October 14, 1863). A futile charge into the murderous fire did not dislodge the stubborn Yankees. By the time that the Rebels escaped, Hill had lost nearly 1,400 soldiers and a battery of artillery. Following the Union victory at Bristoe Station, Lee called off his short-lived offensive and slowly fell back to the Rappahannock River.

With Lee in retreat, Meade reversed his course and, once again, became the pursuer. On October 19, 1863, Stuart, who was shielding Lee’s withdrawal, lured Union Brigadier-General Judson Kilpatrick and his cavalry into an ambush near Buckland Mills on a small stream named Broad Run. Stuart’s horsemen routed the surprised Union troops and sent them fleeing. The Union retreat was so speedy that the Confederates derisively referred to the Battle of Buckland Mills as the Buckland Races. The next day, Stuart’s cavalry rejoined Lee’s main army.

By early November, the Army of Northern Virginia had safely crossed the Rappahannock River, leaving intact a pontoon bridge at Rappahannock Station. Meade, who was under intense pressure from Washington to continue to pursue Lee’s retreating army, launched an attack on November 7, 1863. Lee hastily shifted troops but did not halt the Federal advance. At dusk, the Yankees surged forward and overran the Confederates guarding the bridge. During the rout, they captured over 1,600 Confederate soldiers from the division of Major General Jubal Early. The Union victory at the Battle of Rappahannock Station forced Lee to retreat even farther south than he had hoped before the onset of winter.

Mine Run Campaign

Meade’s success at the Battle of Rappahannock Station emboldened him to launch another offensive before cold weather arrived. On November 26, 1863, Meade’s 2nd, 3rd, and 5th Corps advanced toward the Rapidan River. Meade planned for each of the corps to cross the river and then quickly to swing west in three columns and attack Lee’s right flank near Mine Run, a small stream flowing north to the Rapidan. The success of the operation depended upon the element of surprise. Unfortunately for Meade, the weather and some poor generalship combined to eliminate any chance he had to catch Lee off guard. By the time the Union forces prepared to launch their assault, Confederate scouts had discovered their whereabouts. Alerted to the Yankees’ presence, Lee quickly dispatched troops to intercept them.

Elements of the two armies collided the next day (November 27) on the east side of Mine Run in a dense tangle of trees and brush locally known as the Wilderness. As both sides hastened to send troops to the front, intense fighting eventually engaged over 16,000 soldiers. After an afternoon of charges and countercharges, neither side could claim a victory when the fighting subsided with the onset of darkness. Veterans on both sides would later recall that day’s action as some of the more intense of the entire war.

During the night, Lee pulled his men back to the west side of Mine Run and began digging in. Meade awoke the next morning to find his adversary well entrenched on the high ground protected by a stream to his front. After shelling the Confederates for the next two days, while unsuccessfully probing for a weakness in Lee’s lines, Meade accepted the futility of launching a hopeless assault against the Rebels. Instead, he wisely turned his army around during the night of December 1–2 and headed north to re-cross the Rapidan. One day later, the Army of the Potomac was safe across the river, and Meade went into winter quarters expecting harsh criticism from the northern press and his superiors in Washington for the failed campaign.

Overland Campaign

On March 10, 1864, President Abraham Lincoln appointed Ulysses S. Grant as General-in-Chief of the Armies of the United States. Upon his arrival in Washington, Grant drafted a plan to get the various Union armies in the field to act in concert. He also devised his Overland Campaign to invade east-central Virginia and destroy the Confederate Army of Northern Virginia. Grant set up his headquarters in the field with the Army of the Potomac and instructed General Meade, “Wherever Lee goes, there you will go also.”

On May 4, 1864, Grant launched the Overland Campaign, when the Army of the Potomac crossed the Rappahannock and Rapidan Rivers. Understanding that he was better equipped to win a war of attrition, Grant engaged Lee in a series of horrific battles over the next two months. Each side suffered thousands of casualties at the Battle of the Wilderness (May 5–June 24), the Battle of Spotsylvania Court House (May 8–21), the Battle of North Anna (May 23–26), the Battle of Cold Harbor (May 31–June 12), and others during the campaign. After each encounter, Grant ordered Meade to disengage and to march the Army of the Potomac farther south. Forced to stay between Meade and the Confederate capital at Richmond, Grant compelled Lee to remain one step ahead of the Northerners and to continue to absorb damaging body blows from the Army of the Potomac.

The Overland Campaign was a strategic success for the North. By pounding at the Army of Northern Virginia, Grant hindered Southern efforts to send reinforcements to halt Union campaigns elsewhere. In addition, although the Army of the Potomac suffered higher casualties (39,000 to 31,500), the Confederacy could not replace their losses as readily. Finally, by threatening Petersburg and, ultimately, Richmond, Grant tied down the Army of Northern Virginia, limiting Lee’s military options for the rest of the war. Despite the strategic success of the Overland Campaign, however, it was not without its critics. Shocking casualty rates and grisly battle conditions stunned war-weary Northerners. Some began to refer to Grant as a butcher, whose strategy of winning by attrition exacted too high of a toll on human life.

Petersburg Campaign

On June 12, 1864, Grant abandoned his strategy of attacking Lee’s army. He ordered the Army of the Potomac to cross the James River to begin an assault on Petersburg, a crucial supply depot for Richmond and Lee’s army, situated south of the Confederate capital. From June 1864 to March 1865, the Army of the Potomac settled into a strategy of siege warfare. Rather than continue to sacrifice soldiers through head-on engagements with Lee, Grant aimed to starve the Army of Northern Virginia, entrenched outside of Petersburg and Richmond into submission by cutting off their supplies. For nine months, the two armies built extensive networks of trenches around Petersburg, as Grant maneuvered his forces around Petersburg to cut off roads and railroads that provided the Confederates with supplies from the south and west. Eventually, the strategy worked. Faced with starvation, Lee pulled out of Petersburg on April 2, 1865. The next day, the Confederate government abandoned the capital at Richmond, and Union soldiers occupied the city.

The Petersburg Campaign was a costly but successful Federal offensive. The Union suffered about 42,000 casualties, compared with 28,000 Confederate losses. Despite the heavy casualties, however, Grant achieved his primary objective of forcing Lee to evacuate Petersburg and Richmond.

Appomattox Campaign

After evacuating Petersburg, Lee marched the Army of Northern Virginia west, hoping to find desperately needed supplies at Lynchburg or Danville, Virginia. From there he planned to move south and unite his army with General Joseph Johnston’s forces opposing Union Major General William T. Sherman in North Carolina. Grant, however, had no intention of letting Lee’s plans come to fruition. Throughout the next week, the Army of the Potomac doggedly pursued Lee’s beleaguered army, winning engagements at Sutherland’s Station (April 2), Sailor’s Creek (April 6), and Appomattox Station (April 8).

On April 7, Grant opened communications with Lee regarding the cessation of hostilities. That night, Lee inquired about “the terms you will offer on condition of its surrender.” The next morning, April 8, Grant generously replied, “there is but one condition I would insist upon,—namely that the men and officers surrendered shall be disqualified for taking up arms against the Government of the United States until properly exchanged.” He once again invited Lee to meet with him to discuss the surrender of the Rebel army. Lee made one last attempt to escape on April 9, but the Federals blocked his flight at the Battle of Appomattox Court House. That afternoon, Lee surrendered his army to Grant.

Grand Review and Discontinuation

Following the Surrender at Appomattox Court House, most of the Army of the Potomac marched back through eastern Virginia towards Washington, DC. By the morning of May 12, 1865, they encamped at Arlington Heights, just outside of the nation’s capital. On the morning of May 23, General Meade paraded his army down Pennsylvania Avenue and through the streets of Washington in front of thousands of citizens, who had assembled to show their gratitude for the service that the soldiers had rendered. The procession eventually passed before a reviewing stand near the White House, where President Andrew Johnson, General-in-Chief Grant, and other government dignitaries saluted the troops, who passed by for over six hours.

On June 28, 1865, General Meade issued General Orders No. 35, announcing that the Army of the Potomac “as an organization, ceases to exist.” Troops not “already directed to be mustered out” were merged into a provisional corps commanded by Major General Horatio G. Wright for the purpose of initiating their separation from the volunteer army. Over the course of the next few weeks, the men of the Army of the Potomac returned to their home states, where they mustered out of service and returned to civilian life.

Commanders of the Army of the Potomac

During its five-year history, four men commanded the Union Army of the Potomac:

  1. July 26, 1861–November 9, 1862 — Major General George B. McClellan
  2. November 9, 1862–January 26, 1863 — Major General Ambrose E. Burnside
  3. January 26–June 27, 1863 — Major General Joseph Hooker
  4. June 27, 1863–June 28, 1865 — Major General George G. Meade

Citation Information

The following information is provided for citations, including APA Style, Chicago Style, and MLA Style.

  • Article Title Army of the Potomac (USA)
  • Date 1861–1865
  • Author
  • Website Name American History Central
  • Access Date June 21, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update March 16, 2024