The Army of the Potomac

by Lawrence A. Kreiser, Jr.

The Army of the Potomac deserves a claim as the best army of the Civil War because it accomplished the most difficult tasks.

Ask anyone interested in American history to name the most formidable army of the Civil War and a lively debate is likely to ensue. Many people will argue for the Confederate Army of Northern Virginia. Led by General Robert E. Lee, the Army of Northern Virginia fought ferociously and came closer than any other Rebel army to winning the war for the Confederacy. Other scholars and fans of the Civil War will advocate for the Union Army of the Tennessee. From Shiloh to Atlanta and beyond, the Army of the Tennessee, in the words of its leading historian, knew “nothing but victory.”[1]

Fewer people will claim the Union Army of the Potomac as the premier fighting force of the Civil War. Upon making the argument, they might face a rather vigorous counter attack. Search the Internet for the Army of the Potomac, and descriptions such as “bumbling;” “overwhelming numbers;” and “disappointment” appear with a surprising frequency.

Yet the Army of the Potomac deserves a claim as the best army of the Civil War because it accomplished the most difficult tasks. Between 1861 and 1865, the Army of the Potomac defended Washington, D.C., captured Richmond, Virginia—the Confederate capital—and destroyed Lee’s army. These three accomplishments came at a staggering human cost. At Antietam in 1862, the Union army lost 12,400 soldiers killed, wounded, and missing in one day of combat. The next year, during three days of fighting at Gettysburg, the Army of the Potomac suffered another 23,000 casualties. “No other Union army opposed such a formidable foe, fought more battles, incurred more casualties, and withstood more command turmoil than the Army of the Potomac,” declares Jeffry Wert, a leading scholar of the war in the East. “At times, its soldiers despaired of the outcome and cursed their leaders. But they remained devoted to the cause . . . . Resiliency became one of their defining characteristics.”[2]

The Army of the Potomac ended the war in triumph, but its origins began in the Union defeat at Bull Run in the summer of 1861. Under the command of Brigadier General Irvin McDowell, a Union army marched from Washington in the first of many northern attempts to capture Richmond. After a hard-fought battle against Confederate forces at Manassas Junction, a railroad center about 30 miles southwest of Washington, the Union army collapsed into a rout on the late afternoon of July 21. Federal soldiers streamed back into the nation’s capital over the next several days, disheartened and disorganized.

President Abraham Lincoln appointed Major General George Brinton McClellan to command the Union forces in and around Washington the day after the fighting at Bull Run, marking the official beginnings of the Army of the Potomac. An able administrator, McClellan brought organization to the seeming chaos he found everywhere throughout his new command. McClellan organized three to four regiments—the basic building block of American armies since the Colonial era and, during the Civil War, numbering 1,000 officers and men—into brigades. The American military had most recently deployed brigades during the fighting with Mexico (1846-48). McClellan organized two to three brigades into a division. The ten divisions in the Army of the Potomac ranged in manpower by late 1861, from the largest at 14,900 men, to the smallest at 8,300 men. By contrast, and showing the magnitude of the Union war effort in the East, the American army that had captured Mexico City in 1847 numbered about 12,000 men.

McClellan organized his forces into army corps in early 1862, but only because Lincoln and Secretary of War Edwin Stanton left him no choice. Army corps were groupings of divisions that might maneuver either independently or in cooperation, as the military situation demanded. Americans had never created corps because no army had reached a size to warrant their use. European armies had used the formation since the Napoleonic Wars, allowing them to achieve a high level of operational mobility. McClellan thought the creation of army corps fine only in theory. A conservative Democrat who fought to preserve the Union, McClellan worried that Lincoln and Stanton might appoint as corps commanders generals who were sympathetic to the Republican Party. The so-called Radical Republicans in Congress already were calling for a war to smash the Confederacy and its social structure. In March, Lincoln and Stanton ordered the army divided into four corps, each with between two and three divisions. They also appointed the four corps commanders. These generals were the senior-ranking division officers in the Army of the Potomac. Each of the four corps commanders also was either a supporter of the Republican Party or, the next best thing for Lincoln, a political neutral.

The soldiers who served in the Army of the Potomac by the spring of 1862 came heavily from the East. About 155 regiments (infantry and cavalry) and batteries (artillery) served in the army in April. Only nine of these units came from a state outside of the New England and Mid-Atlantic regions. The Army of the Potomac also listed some of the more hard fighting, and colorful, brigades in the Union army. The Irish Brigade fielded many Catholic immigrants from “Erin’s Isle” and carried green regimental flags into battle; the Philadelphia Brigade bore the name of its home city, the only Union brigade to do so; the Excelsior Brigade marched from New York under the command of the notorious Democratic politician and womanizer Brigadier General Daniel Edgar Sickles; and the New Jersey Brigade gained by 1865 the distinction of having fought in the thick of many of the great battles in the East.

These men fought primarily to preserve the Union. Certainly some of the “boys in blue” had volunteered to satisfy a sense of adventure, or to receive a steady, albeit dangerous, monthly pay. More soldiers, however, desired to protect the American Union. No group of peoples had a right to withdraw from the United States whenever they became unhappy, or else the American nation simply would not work. Soldiers filled their letters and diaries about fighting to protect “our great and free government;” “the best government;” and “law against disorder.”[3] Although an abstract concept, the American Union was worth fighting and, if need be, bleeding, to preserve.

The Army of the Potomac experienced its apprenticeship in arms in Virginia and Maryland during 1862. Attempting to capture Richmond while supplying his own army through more secure river routes (rather than overland), McClellan sailed his army to the Virginia Peninsula in the spring. Moving the army by water to Fort Monroe, Virginia, was an impressive logistical accomplishment, but the resulting Peninsula Campaign never met the war-winning expectations of the Union. The Army of the Potomac had pushed to within a handful of miles from Richmond by late June, before a series of vicious Confederate counterattacks during the Seven Days Battles forced a general retreat. By mid-August, the Union army was embarking on steamers and troopships for a return voyage to the Washington defenses.

Following the Union defeat at Second Bull Run in late August, the Army of the Potomac again took the field. General Lee and his Confederate army had invaded Maryland, in the hopes of fighting a war-winning battle on northern soil. After a series of maneuvers and skirmishes, the Union and Confederate armies gathered around Sharpsburg and Antietam Creek in western Maryland on September 16. The next morning began the bloodiest single-day battle in American history. The Corn Field, West Woods, Sunken Road, and Burnside’s Bridge entered the American lexicon as names of carnage and bravery. Although a tactical draw, Antietam became a strategic Union victory when the Confederate army retreated back to northern Virginia on September 19.

The Army of the Potomac had fought well on the Virginia Peninsula and in western Maryland, but had little to show for the overall effort. The clear-cut Union battlefield triumph at Malvern Hill on July 1 had prompted one Confederate general to bemoan “It was not war—it was murder.”[4] Yet, the next day, McClellan was again in retreat, this time to Harrison’s Landing. At Antietam, the Union II Corps had stormed the Sunken Road and cracked the center of the Confederate defensive lines, to have an overly cautious McClellan commit no reserves to exploit the breakthrough. If the war seemed no closer to ending as summer merged into fall, the timidity of the high command, rather than the valor of the common soldier, is where the blame deserves to fall.

Battlefield setbacks understandably tend to shake morale, but the Army of the Potomac experienced some of its darkest defeats in northern Virginia during late 1862 and early 1863. Following the Maryland Campaign, President Lincoln replaced McClellan as commander of the Army of the Potomac with Major General Ambrose Everett Burnside. For one of the few times during the war, the Union army stole a march on the Confederate army. Burnside had his forces—now numbering six corps and 110,000 officers and men—to Falmouth. From here, Burnside hoped to cross the Rappahannock River and seize Fredericksburg, before continuing to move south and toward Richmond. The pontoon bridges to help the Federal army cross the Rappahannock had not yet arrived, for reasons still debated. (bureaucratic muddle? unclear orders from Burnside? One might find in the source materials arguments for either side of the question.) Lee’s army soon did. Burnside—feeling frustrated by the bridging snafu and pressured by Lincoln to do something, if at all practical—threw the army into the offensive at Fredericksburg in mid-December. A promising attack against the Confederate right was little pushed, while a disastrous attack against the strongly held Confederate left was overly reinforced. The stone wall and Marye’s Heights entered the pantheon of terrible places where the Army of the Potomac fought bravely and, ultimately, futilely.

That spring, the Army of the Potomac, now under the command of Major General Joseph Hooker, launched yet another offensive to capture Richmond and win the war. In an initially well-executed plan, like the march to Falmouth in November, the Army of the Potomac found itself in a promising strategic situation. Hooker had maneuvered about 75,000 Union soldiers around the Confederate left flank and several miles behind Fredericksburg by April 30. Another 40,000 Union soldiers stood poised to strike across the Rappahannock River and through Fredericksburg. On the cusp of enveloping the Confederate army, Hooker turned cautious (also for still debated reasons). Lee seized the initiative and, in a brilliant attack, smashed the Union right flank on the evening of May 2. Four days later, the Army of the Potomac retreated back to Falmouth.

The Emancipation Proclamation only worsened morale following the defeats at Fredericksburg and Chancellorsville. Declared in the autumn of 1862 and implemented at the start of the next year, the Emancipation Proclamation broadened the Union war aims to include the destruction of slavery. The Emancipation Proclamation also allowed African Americans into the Union military as soldiers (although, in the Federal army, serving in black regiments commanded by white officers). Many of Hooker’s soldiers initially responded poorly. A common complaint ran that they had volunteered to preserve the Union, not to fight and die to free the slaves. Criticism of the Emancipation Proclamation began to die away as soldiers realized its military significance. Every slave freed took away a worker from the Confederate war effort and, if a young man, added a potential soldier to the Union army. Still, in early 1863, discontent against the expansion of the Union war effort ran high.

Better days were ahead for the Army of the Potomac, although soldiers might not have guessed as much when they marched north to defend against another Confederate invasion in mid- and late June. Attempting to stay between Washington and the fast-marching Army of Northern Virginia, the Army of the Potomac crossed into Maryland and southern Pennsylvania. Confederate and Union soldiers clashed around the crossroads town of Gettysburg on July 1, the beginnings of one of the most famous battles in American history. Over the three days of fighting, the Army of the Potomac was mostly on the defensive. With the defeat of Pickett’s Charge on the afternoon of July 3, the Union army had won a clear battlefield victory. The ensuing Union pursuit of Lee’s battered army failed to force a war-ending showdown. Reflecting on the fighting at Gettysburg, however, buoyed soldiers’ spirits. Union casualties had been heavy, but the army had won a victory widely heralded across the North.

In a rare occurrence, the war in the East took a backseat to the fighting in the West during the late summer and fall of 1863. Major General George Gordon Meade, who had assumed command of the Army of the Potomac just prior to Gettysburg, and General Lee maneuvered and counter-maneuvered across northern Virginia during the Bristoe Station Campaign in October and the Mine Run Campaign in late November and early December. Tired and with blistered feet, soldiers consoled themselves by reading in the newspapers about the Union battlefield victories at Lookout Mountain and Missionary Ridge, outside of Chattanooga, Tennessee, in the late autumn.

The volunteers of 1861 faced the decision of whether to reenlist as the Army of the Potomac went into winter quarters around Stevensburg, Virginia, in late 1863 (Civil War armies, like military forces from almost the beginnings of civilization, did not fight around the calendar because the logistics of maneuvering large numbers of men through the snows of winter and the rain and mud of early spring were simply too difficult to surmount). At the start of the war, Union soldiers had enlisted for a three-year term of service. Faced with the decision of whether to stay in the army, about one-half of the war’s first volunteers reenlisted. Secretary of War Stanton had sweetened the deal, allowing newly designated “veteran volunteers” a furlough home and the right to wear a special chevron on their uniform sleeve. More important, because the soldiers who had not reenlisted would be going home that spring and summer as they mustered out, veteran volunteers remained committed to the Union cause. They continued to believe the American republic the “best government in the world” and the fight to preserve it a “sacred cause.”[5]

While at Stevensburg, the army underwent its most significant reorganization since the start of the war. Citing heavy Union casualties at Gettysburg, Meade reduced the number of army corps from five to three. By the third winter of the war, soldiers had a strong sense of identity with their corps. The soldiers of the two disbanded corps expressed a bitterness that, for some, lasted through the remainder of their military service. The reorganized army, however, was a formidable military force. The three corps commanders all were experienced combat officers. They each led three to four divisions; about 120,000 officers and men, in total. The streamlined Army of the Potomac now had the ability to launch battlefield attacks with almost overwhelming numbers of men, like the Confederate Army of Northern Virginia had at Chancellorsville and, more recently, at Gettysburg.

The command structure of the Army of the Potomac worked less well. That winter, Lincoln had appointed Lieutenant General Ulysses S. Grant as general-in-chief of the Union army. Not wanting to command from Washington, Grant took the field with the Army of the Potomac. A tension sometimes existed between whether Grant or Meade was issuing the direct orders to the army. Additionally, the Union IX Corps marched with the Army of the Potomac. Because the commander of the IX Corps was senior to Meade, his command, at least on paper, was responsible only to Grant. Such command tangles were dangerous when readying to confront Lee and his vaunted Confederate army.

The Overland Campaign that spring was one of the more brutal of the Civil War, and certainly in American military history into the twentieth century. Taking the field in early May, the Army of the Potomac repeatedly attempted to maneuver around the Confederate army’s right flank. If successful, Grant would be between Lee and Richmond. The Confederate army moved more quickly—sometimes just barely—and at each turn the Army of the Potomac bumped into strong Rebel defensive works. The Wilderness, Spotsylvania Court House, and Cold Harbor all were hard-fought battles through mid-June. Even when not engaged in a major combat operation, Union and Confederate soldiers were marching and skirmishing almost every day. Rations had trouble keeping pace, and the heavens seemed to alternate between broiling sun and drenching rain. Daily existence became something to endure during the five weeks of the Overland Campaign.

That they had might offer a grim satisfaction unavailable to many Union soldiers. Between May 4 and June 12, the Army of the Potomac had lost about 2,000 men to sickness and battle, on average, every day. The payment was high, but the Army of the Potomac had inflicted an even higher ratio of punishment on its adversary. About one-half of the 64,000 Confederate soldiers who took the field at the start of the campaign were killed, wounded, or captured by its conclusion.

With the Union army bloodied and stalled before strong Confederate defensive works at Cold Harbor, a crossroads town almost due east from Richmond, Grant stole a march on Lee in mid-June. Grant hoped to have his men across the James River and into Petersburg, a major transportation hub about 20 miles south of Richmond, before Lee had time to respond. Petersburg under Union control would cut Confederate supply lines to the interior and force the abandonment of Richmond. As was often the case during war, the plan did not match the reality. The hard marching and heavy fighting of the past many weeks resulted in feebly delivered Union assaults that, when combined with command bungles, made little impression against the Confederate defensive works at Petersburg. Worse, by June 18, the Lee’s men had arrived to defend the lines. A Union attack later that day only resulted in increasing the already lengthy northern casualty lists.

Soon after the failed Union assault, Grant settled into a siege of Petersburg. For the remainder of 1864 and into the spring of 1865, Union and Confederate soldiers dug entrenchments, dodged snipers and artillery bursts, and attempted to hang on. The nine-month siege was the longest sustained operation of the Civil War. An American soldier on the Western Front in 1917 or the Normandy hedgerows in 1944 might more readily recognize the static warfare around Petersburg than a Union or Confederate soldier who had fought at Bull Run, Antietam, Gettysburg, or almost any other earlier Civil War battle. The few battles that were fought before Petersburg—the Crater in July; Deep Bottom and Reams Station in August; Hatcher’s Run in February—continued to tip the siege in favor of the Union by wearing down Confederate manpower and logistics.

Soldiers of the Army of the Potomac had the opportunity to help determine the direction of the Union war effort during the presidential election of 1864. The first presidential election held in wartime offered northerners the choice of Abraham Lincoln and George McClellan, the former commander of the Army of the Potomac. Lincoln pledged to continue the war until the Union was restored and slavery destroyed. McClellan countered by offering to negotiate with the Confederacy to restore the Union as it was in 1860. Voters had a clear choice: to continue the war until the Union triumphed, or to concede that a United States free from slavery was not worth the continuing cost in blood and treasure.

The citizen-soldiers of the Army of the Potomac did not see the presidential contest as a difficult decision to make. By a wide margin, they cast their ballots for Lincoln and the continuation of the war until the Union had triumphed. The vote tallies are hard to determine precisely because some soldiers received a furlough to cast their ballot at home; and other soldiers were not permitted by their home states to vote from a distance. But General Meade later estimated that 70 percent of the soldiers in his army had voted for Lincoln. Across the rest of the Union, Lincoln received 55 percent of the popular vote.

With a dash reminiscent of the start of the war levied against the hard-won military experience of nearly four years of fighting, the Army of the Potomac stormed the Confederate defensive lines at Petersburg in early April 1865. The Union capture of the city forced the Confederate army to abandon Richmond on April 2. The next week witnessed the two armies marching westward, with Grant skillfully hemming in Lee’s remaining escape routes. At Saylers’ Creek on April 6, the Army of the Potomac trapped and captured about 8,000 Confederate soldiers. Three days later, surrounded by blue-clad infantry and cavalry, Lee surrendered his remaining soldiers at Appomattox Court House.

The Army of the Potomac has, arguably, fared less well in the battle for the memory of the Civil War. William Swinton, a wartime correspondent for The New York Times, wrote one of the first unit histories of the Civil War. Published in 1866, Campaigns of the Army of the Potomac weighed a hefty 600 pages. All of this because Swinton hoped to win for the Army of the Potomac the “recognition which is justly its due, but which had not yet been accorded it.”[6] Through 2013, according to the Library of Congress, another 937 titles have appeared on “Mr. Lincoln’s army.” The three-volume history penned by Bruce Catton in the 1950s remains among the most beloved and widely read books on the Civil War.

And yet—the reputation of the Army of the Potomac suffers from where and whom it fought. Located always within the political glare of Washington, the army was often subjected to military and civilian intrigue. McClellan and Hooker whispered about the need for a military dictatorship. The Committee on the Conduct of the War, dominated by Radical Republicans, sometimes seemed more interested in attacking Democratic generals than allowing the Union army to fight the war. An almost perceptible sense of caution pervaded the high command until the coming of Grant. Still, other Federal armies had commanding officers who blurred the military with the political. In the West, Major General John C. Frémont attempted to free all of the slaves in Missouri on his own authority during the late summer of 1862. Nearly three years later, Major General William Tecumseh Sherman attempted to negotiate his own peace terms with Confederate General Joseph Eggleston Johnston in North Carolina.

The Army of the Potomac’s reputation also suffered because it not only had to fight—but attack and defeat—Robert E. Lee. The Confederate general likely would rate highly in any compilation of great military leaders. The Union eventually won the war in the East not by a climatic open-field battle, but by wearing down the Confederate army through maneuver and attrition. Lee, in a farewell address to his soldiers after the surrender at Appomattox, emphasized only the attrition. “The Army of Northern Virginia has been compelled to yield to overwhelming numbers and resources.”[7] Confederate veterans picked up the theme. The myth of the Lost Cause emphasized the heaviest battalions, especially in explaining the defeat of the Confederacy’s most famous general and army.

To put the accomplishments of the Army of the Potomac into perspective, perhaps it is fitting to go back to an article run in The New York Times as Grant accepted the surrender of Lee. The unidentified author—perhaps William Swinton—summarized the career of the “The Grand Old Army of the Potomac.” That Union army “has done its work. It has captured Richmond, it has demolished Lee. Its unparalleled trials have been rewarded by unparalleled success.” From its organization during the summer of 1861, the Army of the Potomac “has always occupied the foreground of the war, and all brilliant exploits elsewhere could but momentarily draw the public eye from it. Everybody felt that on its strong right arm mainly depended the fate of the nation.” McClellan, Burnside, and Hooker would not go into the history books as war-winning generals. However, whatever “may have been the defects of its former commanders, it is certain that the rank and file of the army have never been wanting.” Other Union armies also had won great battlefield victories. Yet the Army of the Potomac “ought always to be remembered as the army that was pitted against the very head and front of the rebellion, and that sent it finally to dust. Every living man who has faithfully served in that army deserves unfading laurels. And would that every one of the tens of thousands of its heroic dead could have a monument as perdurable as the republic.”[8]

  • [1] Steven E. Woodworth, Nothing but Victory: The Army of the Tennessee, 1861-1865 (New York: Alfred A. Knopf, 2005).
  • [2] Jeffry D. Wert, The Sword of Lincoln: The Army of the Potomac (New York: Simon and Schuster, 2005), 415-416.
  • [3] Charles Benson, diary entry, December 31, 1861, in The Civil War Diaries of Charles E. Benson, ed. Richard H. Benson (Decorah, Iowa: Anundsen Publishing, 1991), 33;  George Beidelman to father, May 15, 1861, in The Civil War Letters of George Washington Beidelman, ed. Catherine Vanderslice (New York: Vantage Press, 1978),  15.  Also see, James M. McPherson, For Cause and Comrades: Why Men Fought in the Civil War (New York: Oxford University Press, 1997), 17-19; and, James I. Robertson, Jr., Soldiers Blue and Gray (Columbia: University of South Carolina Press, 1988), 1-11.
  • [4] Daniel H. Hill, “McClellan’s Change of Base and Malvern Hill,” Battles and Leaders of the Civil War, vol. 2 (New York: The Century Co., 1887-1888), 394.
  • [5] Edmund English to Mother, April 22, 1864, in McPherson, For Cause and Comrades, 174-175.  Also see Wert, The Sword of Lincoln, 322-24; and John J. Hennessy, “I Dread the Spring: The Army of the Potomac Prepares for the Overland Campaign,” in The Wilderness Campaign, ed. Gary W. Gallagher (Chapel Hill: University of North Carolina Press, 1997), 70-75.  
  • [6] William Swinton, Campaigns of the Army of the Potomac: A Critical History of Operations in Virginia, Maryland, and Pennsylvania, from the Commencement to the Close of the War, 1861-5 (New York: Charles Scribner’s Sons, 1882), 623.  Swinton’s book is accessible online, through the Internet Archives (sponsored by the Library of Congress), at: (Accessed October 6, 2014). 
  • [7] U.S. War Department, The War of the Rebellion: A Compilation of the Official Records of the Union and Confederate Armies (Washington, D.C.: Government Printing Office, 1894), series I, vol. 46, pt. 1, 1267.
  • [8] “The Grand Old Army of the Potomac,” April 8, 1865, The New York Times, listed at:  (Accessed October 6, 2014).   

If you can read only one book:

Catton, Bruce The Army of the Potomac. 3 vols. Mr. Lincoln’s Army. Glory Road. A Stillness at Appomattox. New York: Doubleday, 1951-1953.


  • Beatie, Russel H. The Army of the Potomac. 3 vols. Birth of Command, November 1860—September 1861. McClellan Takes Command, September 1861-February 1862. McClellan’s First Campaign, March-May 1862. El Dorado Hills, CA: Savas Beatie, 2002, 2004, 2007.

  • Davis, William C. Lincoln’s Men: How President Lincoln Became Father to an Army and a Nation. New York: The Free Press, 1999.

  • Kreiser, Lawrence A. Defeating Lee: A History of the Second Corps, Army of the Potomac. Bloomington: Indiana University Press, 2011.

  • Wert, Jeffry D. The Sword of Lincoln: The Army of the Potomac. New York: Simon and Schuster, 2005.


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Web Resources:

  • The battlefields of the Army of the Potomac are searchable through the National Park Service website.

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  • The Civil War Trust has a range of information for teachers and students including material on the Army of the Potomac and the battles it fought.

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Other Sources:

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