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“Irreparable losses”: a reappraisal of George B. McClellan at Antietam

Scott Reeves
University of Sheffield

The Battle of Antietam has become a symbol of the carnage and attrition of the American Civil War. On September 17 1862, the Union and Confederate armies – commanded by Maj. Gen. George B. McClellan and Maj. Gen. Robert E. Lee – clashed time and time again. 12,000 soldiers died, in the bloodiest day of the entire war. Since that day, historians have almost universally considered the Battle of Antietam to be the last failure of a failed Federal commander. Labouring under psychological delusions and a mistaken military strategy, which led to perpetual over-caution and over-exaggeration of the enemy force facing him, Lincoln and the Union had a “horrible predicament to be saddled with McClellan”[i].

However, McClellan’s historical reputation has had the benefit of a small renaissance, courtesy of Thomas Rowland and Joseph Harsh, who describe the too-often damning of “a caricature which is distorted by over-simplification”[ii]. They note that Abraham Lincoln, Ulysses S. Grant and William T. Sherman, as the victorious leader and commanders, are portrayed favourably in histories of the Civil War. In this situation, “McClellan cannot and does not fare well by contrast”[iii]. However, McClellan was the commander of the Federal armies at a time when Confederate morale and material resources were at their strongest. In such a situation, he faced a near impossible task, much more difficult than that inherited by Grant in the later years of the war. In the light of these new reappraisals, can the Battle of Antietam, McClellan’s last set-piece battle as the commander of the Army of the Potomac, also be reconsidered?[iv]


Maj. Gen. Joseph Hooker must have spent a restless night in Miller’s barn on September 16-17 1862. He was with Brig. Gen. Truman Seymour’s brigade – the most advanced unit of the Army of the Potomac, yards from the crucial Hagerstown Road. At 9.00pm, he investigated rifle-fire in the lines of pickets, and found that his troops were so close to the rebels that they could hear footsteps, but they were unable to see the enemy.

Merely two days earlier, on September 14, the Federal army had won a victory at the Battle of South Mountain. George McClellan thought that his priority was to push the Confederate invaders out of Maryland. The President would have preferred the Army of Northern Virginia crushed against the Potomac River, forcing Robert E. Lee’s surrender, and destroying the vehicle with which the rebels could fight. “Fighting Joe” Hooker must have realised that the impending battle would be crucial for the outcome of the whole war. Little did he realise that his own misfortune would be exploited by McClellan to explain the failure of the Union army to gain a total victory.

The Confederate commander, Robert E. Lee, had chosen an excellent battlefield to make his stand against McClellan. Although the Potomac River was at his back, making retreat almost impossible, the Confederates had nestled into a meander. Both flanks were protected from a sweeping attack by the flowing water, forcing McClellan into a frontal assault. The Antietam River, believed to be crossable only via four bridges, ran between the two positions, delaying the time that it would take the Union army to strike against the Confederates. Once the Antietam was behind them, the Federal soldiers would have to cross open fields to fight against a slightly elevated enemy. These were optimum conditions for the defensive use of the rifled musket, which would prove so deadly against frontal assault at Fredericksburg.

Faced with a literally uphill task to defeat the Confederates, McClellan’s plan of battle was simple. He determined to attack the left flank of Lee’s army at first light with two or three corps. When that attack began to make progress, and when the enemy began to reinforce her left, Maj. Gen. Ambrose Burnside was to lead an attack on the right flank. With both flanks dissolving, McClellan would then throw the remainder of his force at the centre, drowning the Army of Northern Virginia in the Potomac River.


The Battle of Antietam began at first light, 5.30am. I Corps, commanded by Joseph Hooker, had crossed the Antietam the previous afternoon, and the advance guard of Truman Seymour skirmished with the Confederate pickets whilst the rest of the corps moved into position. XII Corps, under Maj. Gen. Joseph Mansfield, camped one mile behind, ready to support. Hooker’s objective was the capture of the high ground by the Dunker Church three-quarters of a mile in front of him.

In the initial advance of I Corps, the First Division was positioned to the right of the line, with the Second Division on the left. Brig. Gen. George Meade held the Third Division slightly behind, ready to aid whichever side was necessary. Initial resistance came from Thomas Jackson’s Division, the same that had played the crucial role at First Bull Run, when it stood firm like the “stone wall” that became its commander’s epithet. Command of the division had now fallen upon Brig. Gen. John Jones. He had taken possession of a thirty acre cornfield between the East Woods and the Hagerstown Road. Bayonets glinting in the sun revealed the Confederate position to the advancing Union troops. Union artillery decimated most of this force – Hooker recalled that “every stalk of corn in the northern and greater part of the field was cut as closely as could have been done with a knife, and the slain lay in rows as precisely as they had stood in their ranks a moment before”[v].

After this initial success, Hooker’s momentum faltered, and he called up XII Corps at 7.30am to reinforce the Federal line. During the movement, the Army of the Potomac suffered its first major officer casualty of the day. Joseph Mansfield, referred to by McClellan as “the gallant veteran”[vi], and almost universally praised in the reports of the leading Union commanders at Antietam, was mortally wounded whilst in front of his troops. The corps contained a number of new and inexperienced regiments, and had approached the field in some disorder. Mansfield was supervising the reformation of an orderly line when he was struck. The loss of morale and chaos in administration caused by his removal must have been considerable. Indeed, Mansfield was one of only three Union corps commanders killed in action throughout the entire war.

At approximately the same time that Mansfield fell from the saddle, Brig. Gen. George Hartsuff and Col. William Wainwright were taken from the field. Both were commanding brigades in I Corps, and were wounded whilst continuing the offensive against the remnants of Jackson’s Corps in the cornfield.

Now under the control of Brig. Gen. Alpheus Williams, XII Corps succeeded in renewing Federal progress. Confederate divisions under Brig. Gen. John Hood and Maj. Gen. D.H. Hill held positions within the West Woods and the fields to the west of the Hagerstown Road. Brig. Gen. George Greene’s division advanced at the left of the XII Corps attack, whilst the division of Brig. Gen. Samuel Crawford headed the right. By 9.00am, Union troops had captured the lower end of the West Woods, and the Dunker Church. However, in doing so, they came under considerable fire. Post-and-rail fences along the side of the Hagerstown Road delayed the progress of the advance, and left troops open to the fire of Confederate muskets from the woods and horse artillery from Allen’s Hill. Samuel Crawford was wounded, alongside three brigade commanders, one of whom died from his injuries.

About this time, II Corps – which had crossed the Antietam at 7.30am – was moving up in support. Maj. Gen. Edwin Sumner personally supervised the march of the Second Division, but when the troops penetrated the West Woods and entered the fields on the other side, their tight formation meant that Hood’s small force of artillery and the Confederate divisions of Brig. Gen. John Walker and Maj. Gen. Lafayette McLaws were able to decimate them. The division was reduced from 5,000 men to 2,200 in just 15 minutes. Brig. Gen. Napoleon Dana was wounded and taken from the field, and Maj. Gen. John Sedgwick – commanding the Second Division – was wounded three times. McClellan singled out this commander for specific praise, and recorded that he masterminded the retreat for one hour after his first wound, “animating his command by his presence”[vii].

The remaining divisions of II Corps were to be involved in the ferocious fighting at the Sunken Road, thereafter entitled Bloody Lane. The Confederate command of D.H. Hill was driven back into a track that had, through the passage of time, fallen below the level of the surrounding land. This created a natural rifle-pit, a New World precursor to the trenches of the First World War. With the support of excellent defensive terrain, the Confederates were able to delay the advance of the fresher Union troops. Ultimately, II Corps was able to over-run the Sunken Road, but it cost the life of Maj. Gen. Israel Richardson, commander of the First Division, who was mortally wounded. Brig. Gen. Max Weber was also wounded.

By 1.00pm the heavy fighting on the Union right had ended, and McClellan had possession of the Sunken Road, the Hagerstown Road, the cornfield and the East Woods, but he had not forced the Confederate invaders to the banks of the Potomac. The right flank had carved out an attritional victory, which the politicians in Washington thought enough to trigger the Emancipation Proclamation without it being a hollow gesture. However, McClellan had not won the total victory that the President craved – the destruction of the Army of Northern Virginia.

McClellan laid the blame of the failure of the Union army as a whole squarely upon the shoulders of Maj. Gen. Ambrose Burnside. His “inexcusable delay” on the Union left was, McClellan suspected, the product of a “weak mind turned; that he was confused in action”[viii]. However, Burnside’s failings do not explain the failure of the troops on the right to comprehensively penetrate the Confederate lines. This, McClellan suggested, was due to the high proportion of officers killed and injured, because the removal of leaders on the field of battle inevitably retarded forward momentum.

After the capture of the lower West Woods and the Dunker Church, McClellan noted that “the repulse of the enemy offered opportunity to rearrange the lines, and reorganise commands on the right, now more or less in confusion”[ix]. The time taken to solve the command issues raised by the departure of officers allowed the Confederate troops of Hood and D.H. Hill to regroup and counter further advances. After the taking of the Sunken Road, McClellan visited the right flank, to view personally the situation. He remembered that “Sumner’s, Hooker’s and Mansfield’s corps had met with serious losses, several general officers had been carried from the field severely wounded, and the aspect of affairs was anything but promising”[x]. He ordered no further attacks from the right after this visit.

McClellan was certain that the most influential casualty that the Army of the Potomac suffered was that to Joseph Hooker. Hooker remembers that he fell from the saddle “from loss of blood, having previously been struck without my knowledge”[xi] in his foot. This injury meant that Hooker was taken from the battle, to the banks of the Antietam River. Hooker thought that this occurred before 10.00am, as the Union troops captured the lower West Woods and the Dunker Church.

The injury to Hooker would have had a major impact on the organisation and momentum of the attack. Hooker was the ranking officer on the right flank, with responsibility for XII Corps and II Corps, as well as his own command, I Corps. Brig. Gen. George Meade succeeded to the command of I Corps – as he would later succeed Hooker to the command of the entire army in June 1863. However, the management of the right flank would have been handicapped, with no figure in complete local control to harmonise the attack.

A letter written by McClellan to Hooker three days after the battle leaves us in no doubt that the army commander bemoaned the “unfortunate wound”. In fact, McClellan suggests that Hooker’s injury was the turning-point of the entire battle. He wrote, “had you not been wounded when you were, I believe that the result of the battle would have been the destruction of the entire rebel army, for I know that with you at its head, your corps would have kept on until it gained the main road”[xii].

On the right flank at Antietam, officer casualties must have retarded the Federal attack. Two corps commanders, three division commanders, and five brigade commanders were removed from the action. It seems difficult to accuse McClellan of the old flaw of over-exaggeration, when he wrote that “the death of Mansfield, the mounding of Hooker, Richardson and Sedgwick, were irreparable losses in that part of the field”[xiii].


If McClellan’s explanation for the failure of the Union army to destroy Lee’s Army of Northern Virginia is true, it would be expected that a greater proportion of officers were casualties at Antietam compared to other Civil War battles. However, this is not the case. The Official Records of the Union and Confederate Armies indicate that of 12,410 casualties at Antietam, 620 were officers – a proportion of 5.00%. Compared to other set-piece battles, this proportion is less than average. Only the battles of Second Bull Run, Stones River, and the Wilderness incurred lower officer casualties of 4%. In contrast, at Gettysburg, 6.80% of casualties were officers, whilst at Chancellorsville the proportion was 6.10%, and at Fredericksburg 6.36%[xiv].

Nevertheless, the cold numerical analysis of casualty figures is misleading. The Official Records’ casualty figures encompass the whole of the Antietam battlefield, whilst the majority of officer casualties were suffered on the Union right. Indeed, the only notable loss on the left flank was Brig. Gen. Isaac P. Rodman, commanding the Third Division of IX Corps. Although other battles may have had a higher proportion of officer casualties, they were largely spread equally around the battlefield, rather than being focused in one key area.

Officer casualties at Antietam can be further contained in one key area by considering that all of the losses came in a very short period of time – between approximately 7.30am and 1.00pm. This contrasts other battles, where the officer casualties occurred over a longer period of time, and were therefore more manageable. At Spotsylvania Courthouse, Maj. Gen. George Meade was unfortunate to lose two corps commanders, as McClellan did at Antietam. However, Maj. Gen. Gouverneur Warren, commanding V Corps, was wounded on the first day of battle, May 8 1864. It was not until the following day that Maj. Gen. John Sedgwick – the same commander who was wounded in action at Antietam – was killed. Although the losses of Warren and Sedgwick undoubtedly harmed the Union effort at Spotsylvania, the casualties were on separate days, thereby making it much easier for Meade to reorganise commands.

Perhaps the only Civil War battle that can compare to Antietam in terms of the damage caused by officer casualties is Gettysburg. The battle lasted three days, but on two of them the Union effort was significantly hampered by the loss of important commanders. This meant that Meade, similarly to McClellan after Antietam, felt unable to pursue the wounded Army of Northern Virginia to deal a final, crushing defeat.

In the early hours of the first day at Gettysburg, Maj. Gen. John Reynolds was mortally wounded whilst supervising the movements of I Corps. However, Reynolds, in Meade’s absence, controlled all of the Union forces on the field – I, XI and II Corps. The command structure had to be reshuffled, and Maj. Gen. Abner Doubleday took command of I Corps, with Maj. Gen. Oliver Howard (of XI Corps) assuming responsibility for the field. This was transferred again, later in the afternoon, to Maj. Gen. Winfield Hancock, of II Corps.

The third day of Gettysburg was also dominated by the loss of key Union officers. As Confederate troops clashed with the centre and left of the Union line at 1.00pm, Meade was dealt a double-blow. Winfield Hancock was forced to leave the field injured, relinquishing the command of all the troops in the centre-left. At the same time, Brig. Gen. John Gibbon, who had succeeded Hancock to the command of II Corps whilst he had wider authority, also left the field wounded.

The death of Reynolds and wounding of Hancock created situations somewhat akin to the wounding of Hooker at Antietam. The loss of generals who were not only corps commanders, but who had wider responsibilities on the battlefield, hampered the momentum of the entire army. Had such misfortune not occurred on the first and third days at Gettysburg, the result of the battle might have been a comprehensive Union victory, and a earlier end to the Civil War. Therefore, McClellan regretting the loss of Hooker on September 17 1862 is understandable. Few other times in the Civil War could a commander claim that they had suffered such distorted officer casualties.


Nevertheless, officer casualties cannot be attributed the entire blame for the failure of the Union right to gain a complete victory against the Confederacy at Antietam. Mistakes were made in the field that halted the Federal advance and gave the Confederate left a chance to regroup.

In the II Corps attack after 9.00am, Maj. Gen. Edwin Sumner was obviously anxious to throw his troops into the fray and carry the day for the Union. However, his deployment was haphazard and careless. Maj. Gen. John Sedgwick’s Second Division was launched across the cornfield and through the West Woods in a dense formation more suited to fast marching than battle. Three columns, each consisting of a brigade and merely twenty yards apart, were a sitting-duck target for artillery. Not one regiment was spread out to cover the flanks.

Sumner himself escorted the Second Division into the West Woods. He neglected to instruct the other divisions of II Corps to support the attack. The Third Division was in a good position to cover the left of the Second Division, but without orders from the corps commander, Brig. Gen. William French deviated to the left, intending to strike the Confederate line to the South of the Dunker Church. Maj. Gen. Israel Richardson, commanding the First Division, had been delayed slightly, waiting for Porter’s Corps to fill the gap left by II Corps, but the attack was not postponed to await his arrival and support.

The subordinate generals of II Corps must have advised Sumner against making a rushed, under-strength attack, but he ignored them. As the Second Division broke into the field beyond the West Woods, it was met by Hood’s small force of artillery. Although it only consisted of a few guns, every shot removed ranks of the tightly-formed infantry. This was followed by the attacks of McLaws’ and Walker’s divisions, drawn from the Confederate right. Had the Third Division been ordered to support Sedgwick’s attack, it would have absorbed most of the impact of this counter. Instead, Sedgwick found that his brigade lines were so close that they could not wheel left to face the Confederates, and fell back to the cornfield in much disarray, and with great loss of life. Brig. Gen. Napoleon Dana, an experienced campaigner, remembered that “the fire which was poured upon… the Seventh Michigan was the most terrific I have ever witnessed”[xv].

Sumner’s deployment was rash, and far too careless. Had he moved all three divisions in battle-line through the West Woods, Hood, Walker and McLaws would have found that their counters were no barrier to Federal progress. As it was, Sumner used only one-third of his command, in a suicidal charge. Maj. Gen. James Longstreet claimed that if Sumner had moved the corps as one unit against the Confederate line, he would have forced the battle back to the river bank. It is difficult to disagree with him.

Joseph Hooker, the loss of whom was mourned so much by McClellan, also made mistakes on the Antietam battlefield that disrupted Federal success. Hooker had responsibility for all of the right flank until he was removed from the field, and progress was steady. However, his order for XII Corps to support and relieve I Corps was given too late. In the initial attacks of the morning, I Corps had gained the cornfield, but by the time XII Corps reached the field, I Corps had been forced to pull back into defensive positions, and reinforcements from the centre and right restocked the Confederate lines. On the night of September 17-18, I Corps camped by Poffenberger’s Farm – the same position it occupied the previous night.

Had Hooker attacked the Confederate lines with both I Corps and XII Corps simultaneously, it is difficult to imagine little other than a comprehensive Union victory. Jackson’s, Hood’s and D.H. Hill’s divisions would have been overwhelmed, and Lee would not have had the time to reinforce his left. Moreover, such an attack cannot be considered a risky Union venture, because Hooker would still have had II Corps in reserve, to support a successful attack, or to hold a retreat if necessary. Brig. Gen. Jacob Cox, who commanded IX Corps during the battle, thought that could “Hooker and Mansfield have attacked together – or, still better, could Sumner’s II Corps have marched before day and united with the first onset – Lee’s left must inevitably have been crushed long before the Confederate divisions of McLaws, Walker and A.P. Hill could have reached the field”[xvi].

Hooker also made a basic error in the deployment of his troops during the night before the battle. A few hundred metres to the extreme right of I Corps was a mound known as Allen’s Hill. Hooker neglected to occupy this feature, and later in the morning, Maj. Gen. J.E.B. Stuart ordered his horse artillery to use the “commanding hill” to “bring an enfilading fire upon the enemy’s right”[xvii]. This did great damage to the troops of XII Corps after 9.00am.


On November 7 1862, George McClellan was relieved of the command of the Army of the Potomac, and replaced by Ambrose Burnside. Lincoln bemoaned McClellan’s continuing inaction, and failure to pursue and destroy the Army of Northern Virginia. He reluctantly admitted that “he has got the slows”[xviii]. However, McClellan’s reasons for the Federal failure to crush Robert E. Lee at Antietam are partly vindicated – the progress of the right flank was retarded by an unusually large proportion of officers being killed or wounded in a short space of time. Nevertheless, mistakes were made on the battlefield that gave the Confederates opportunities to defend their lines, and McClellan must bear the ultimate responsibility for the errors on the right flank of his army. 


[i] T.H. Williams, Lincoln and His Generals (New York, 1952), pp vii-viii.

[ii] J.L. Harsh, ‘On the McClellan-Go-Round’, Civil War History 19 (1973), p 113.

[iii] T.J. Rowland, ‘In the Shadows of Grant and Sherman: George B. McClellan Revisited’, Civil War History 40 (1994), p 204.

[iv] The boundaries of space prevent further analysis of factors before and after the battle that warrant attention. This paper is confined to events on the battlefield itself, and does not consider, for example, the discovery of Special Order 191 on September 13, nor McClellan’s non-pursuit of the Confederate army in the days after the battle.

[v] Joseph Hooker Report (Battles of South Mountain and Antietam), from The War of the Rebellion: The Official Records of the Union and Confederate Armies, XXVII, p 218.

[vi] George B. McClellan Report (14 August – 9 November 1862), from Official Records, XXVII, p 56.

[vii] McClellan Report, from Official Records, XXVII, p 57.

[viii] George B. McClellan, McClellan’s Own Story (New York, 1887), p 608.

[ix] McClellan Report, from Official Records, XXVII, p 57.

[x] McClellan Report, from Official Records, XXVII, p 62.

[xi] Hooker Report, from Official Records, XXVII, p 219.

[xii] McClellan to Hooker, 20 September 1862, from Official Records, XXVII, p 219.

[xiii] McClellan, Own Story, p 606.

[xiv] Statistics compiled by self from ‘Return of casualties in the Union forces at the Battle of Antietam’, from Official Records, XXVII, p 200. Also ‘Return of casualties’ in other battles, all in Official Records.

[xv] Napoleon Dana Report (Battle of Antietam), from Official Records, XXVII, p 320.

[xvi] Jacob D. Cox, ‘Bloody Lane was in our hands’, from N. Bradford (ed.), Battles and Leaders of the Civil War (New York, 1956), p 249.

[xvii] J.E.B. Stuart Report (2-20 September 1862), from Official Records, XXVII, p 819.

[xviii] T.H. Williams, His Generals, p 177