The Confederate victory at Second Manassas, August 28-30, 1862, followed victories in the Valley Campaign and the Peninsula. The casualties incurred by the Army of the Potomac included 14,000 killed or wounded of 62,000 engaged, compared to about half of that for the Army of Northern Virginia. Then, on September 1, Stonewall Jackson defeated a Union cohort retreating from the battlefield at Chantilly. General Pope was relieved of command and sent to Minnesota to deal with the Sioux, and was never again involved in the Civil War. Pope would blame Fitz-John Porter for the loss, even though that wasn’t the case; Porter would be heard from again at Antietam but would go through a devastating court martial soon after. One of Pope’s generals said of him, “Suffice to say ... that more insolence, superciliousness, ignorance, and pretentiousness were never combined in one man.”
In this multi-part series, here Lloyd W Klein looks at what happened during the Battle of Antietam itself.
Read part 1 on the background here, part 2 on General McClellan’s Response to Finding the Lost Order here, and part 3 on the battle itself here.
Abraham Lincoln and George B. McClellan at Antietam, Maryland, October 3, 1862. Source: Public domain, United States Library of Congress's Prints and Photographs division under the digital ID cwpb.04351., available here.
Aftermath
The battle was over by 5:30 pm. When the smoke cleared and the guns fell silent, Antietam had inflicted an unprecedented toll: estimated total casualties reached 22,717 men—killed, wounded, missing, or captured—making it the bloodiest single‐day engagement in American history. More Americans died in battle on September 17, 1862, than on any other day in the nation's history. The bloodiest battle in American history was Gettysburg, but its more than 46,000 casualties occurred over three days. Antietam ranks fifth in terms of total casualties in Civil War battles.
The devastation to both armies was profound. Officers, enlisted men & horses were destroyed in huge numbers. The dead and wounded littered the field, and it would take months for the dead to be buried. For years after, and even to this day, the remains of soldiers are still being found, evidence of the battle resurfacing in the form of bullets, cannonballs, horseshoes, and other detritus.
The battle is traditionally considered a tactical draw but a strategic Union victory. Modern scholarship suggests Antietam was both a Federal tactical and strategic victory. The battle inflicted terrible casualties on the Army of Northern Virginia, which was already in the process of disintegrating from straggling. Federal troops broke Confederate lines five times during the fighting, and at no point did Southern forces regain the line they occupied before the battle started. Lee remained in place for another day out of the refusal to abandon his campaign, but that amounted to nothing more than posturing.
Lee stayed on the battlefield overnight He prepared to defend against a renewed assault, which never came. Strategically, the battle was a disaster for Lee. The casualties were catastrophic for an army of his size. The ANV retreated to Virginia, McClellan did not pursue despite myriad orders to do so, and was relieved for the second time as commander.
The figures are staggering. Union losses totaled 12,401 (including 2,108 killed, 9,540 wounded, and 753 missing or captured), while Confederate losses amounted to 10,316 (with 1,546 killed, 7,752 wounded, and 1,018 missing or captured). Britannica additionally notes that officer casualties were especially severe: six generals (three Union, three Confederate) fell in the battle, and about a dozen more were wounded.
Looking at the troops actually committed, roughly 56,000 Federal soldiers engaged on key fronts suffered 12,400 casualties (~22%), while about 37,400 Confederates incurred 10,300 casualties (~27.5%)—meaning nearly one in four combatants on the field was killed, wounded, or went missing. When set against the full armies present (approximately 132,000 Union and 87,000 Confederate), these figures translate to overall casualty rates of about 9% and 12%, respectively—figures that belie the ferocity experienced by frontline units.
In terms of casualty composition, of the 22,717 total:
3,654 men were killed (≈16.1%)
17,292 were wounded (≈76.1%)
1,771 were missing or captured (≈7.8%)
This breakdown roughly mirrors the broader Civil War norm—where about 20% of battle casualties were deaths and 80% were wounds—but Antietam’s sheer scale set a grim benchmark, producing the highest single‐day body count in U.S. military history.
Every historian includes or excludes various units, which may or may not be considered to be part of the battle. Sears, for example, gives lower figures. The desertion rate of the Confederate forces is another major area of contention. According to the Washington Post, these traditional figures are skewed. In his after-action report, McClellan claimed that his men buried 2,700 Confederates on the Antietam battlefield and captured 6,000 more. He could only guess at the number of wounded, but he estimated it was 18,742 men, using the ratio of killed to wounded for his own troops.
This stands in stark contrast to Confederate reports, which claimed losses of 1,674 dead, 2,292 missing and 9,451 wounded — a total of 13,417. Even discounting the wounded, the discrepancy between the two reports is almost 5,000 casualties.
Which is right? The burial grounds would indicate that McClellan’s number is closer to the truth. More than 3,300 dead rebels specifically associated with the Antietam campaign can be found buried in the Confederate cemeteries in Hagerstown, Frederick, Shepherdstown and Winchester. This number is larger than McClellan’s because it includes bodies buried by the Confederates themselves as well as those who died shortly after the battle.
Perhaps the most important misconception is the number of troops Lee brought with him during his invasion. Most historians cite McClellan as having had 87,000 men and Lee around 40,000. These numbers are often used for the entire three-week campaign, with the Confederates sometimes credited with as many as 55,000 men, 15,000 of whom straggled off before the battle. But there are no complete returns for Lee’s army until Oct. 10, 1862. Every historian’s count is merely a best-guess estimate.
Lee filed his first return five days after the battle, noting the count is “very imperfect” and does not include cavalry or artillery. It states that on Sept. 22, he had at least 36,418 infantry. Adding a conservative number of 5,000 for the missing cavalry and artillery units would bring his total to about 41,000 troops at the end of the campaign.
Eighteen days later, on Oct. 10, Lee filed his first complete report, which showed 64,273 present for duty. This number is significant because Lee had not received a single new regiment to replace his losses; nor did he receive many, if any, recruits because the February draft law had already pulled every eligible man into the army by early summer. If we add Lee’s reported campaign losses of 13,417 (which, as already noted, are too low), it would show that Lee started the campaign with at least 75,000 men. My final answer is that a lot of people died or were wounded, but we really will never know exactly.
IF this is true, McClellan’s supposed outsized numerical advantage is overstated, and his potential to have annihilated Lee is exaggerated. The army he drove back was not much smaller than his own. He did it without proper cavalry support, with his superiors hoping to oust him and with a significant portion of his army untrained. And as it turns out, he inflicted more damage on Lee’s army than anyone suspected.
Lee’s Retreat
Lee was just lucky to have gotten out of Antietam intact. It was a horrible day for him. He had divided his army numerous times and had not planned to be attacked while Jackson was at Harpers Ferry and Longstreet was at Suffolk. Losing armies in retreat are by definition at their most vulnerable, but for that very reason, at their most dangerous.
On September 18, the armies remained in their positions without fighting. By this point, Lee was highly vulnerable. His army had its back to the Potomac River, just a few miles away, and a quarter of his force had been lost in the previous day’s battle. And after more than two weeks of marching, his men were tired. McClellan, on the other hand, welcomed thousands of additional troops on September 18. But, although he outnumbered Lee’s troops by almost three times, McClellan did not pursue Lee. In fact, despite constant urging from President Abraham Lincoln and Chief of Staff Henry Halleck, McClellan did not move toward Virginia for over a month. McClellan overestimated the size of Lee’s force, assuming that Lee had nearly 100,000 troops in his command, and insisted that the fall of Harpers Ferry, Virginia, on September 15 allowed an additional 40,000 Confederate troops, in his inflated estimation, to fight at Antietam.
Once again, though, modern scholarship has shifted this traditional view. The newest thought points out that McClellan did not pursue Lee because his own army was in no position to give battle. They note that this Union force was in reality four separate commands and that with the battlefield losses, it lacked a unified command structure to organize a movement. The Battle of Shepherdstown, in which just a small part tried to pursue at Shepherdstown (or Botelers) Ford the next 3 days, resulted in a small-scale disaster. Undoubtedly, the units engaged were in bad shape: on September 17th, the 1st Corps suffered 27 % casualties, the Second 31%, the 9th 20 %, and, lastly, the 12th Corps lost 22%. Antietam NPS ranger Keith Snyder has stated that during the battle, there were, in both armies, at least 300 corps, division, brigade, and regimental command changes. In the Federal army alone, there were close to 600 officers, below the rank of colonel, who were either killed or wounded. Not only were the rank and file slaughtered, the command structure was decimated as well.
The post-Antietam messages and reports in the Antietam Official Records contain numerous requests for supplies ranging from ammunition, blankets, shoes, rations, and food. Horses were a major problem. Union horses had also suffered severe casualties. Although Lincoln famously pooh-poohed this concern ("What have your horses done that they are fatigued?”), the Union Army couldn’t move anywhere without the replenishment of the major transportation modality.
Lee retreated across the Potomac River at Shepherdstown Ford, also called Boteler’s Ford: After several days of maneuvering and skirmishing with Union forces, Lee's army crossed the Potomac River at Shepherdstown Ford on September 19-20, 1862. This crossing allowed them to retreat back into Virginia after the Battle of Antietam.
The Battle of Shepherdstown on September 20th. There were 624 casualties—363 Union and 261 Confederate. The Battle of Shepherdstown is one of the largest engagements fought in the modern state of West Virginia (it was still Virginia at the time of the battle in 1862). It was largely inconsequential in the course of the Antietam Campaign because it essentially harassed, but did not stop, Lee’s retreat.
Bodies of Confederate dead gathered for burial after the Battle of Antietam. Source: Public domain, United States Library of Congress's Prints and Photographs division under the digital ID cwpb.01094, available here.
Lincoln Pays a Visit
Meanwhile, President Lincoln was severely disappointed in McClellan's performance both during and after the battle. He believed that McClellan's overly cautious and poorly coordinated actions in the field had caused the battle to be a tactical draw rather than the overwhelming Confederate defeat it really should have been. The president was even more astonished that from September 17 to October 26, despite repeated entreaties from the War Department and the president himself, McClellan declined to pursue Lee across the Potomac, citing shortages of equipment and the fear of overextending his forces.
Famously, President Lincoln came to visit General McClellan on October 3rd. As you can clearly see from the photo, the temperature of the meeting was frosty. As these stiff poses suggest, the personal relationship between the general and the president remained awkward. Abraham Lincoln spent four days travelling over the field, just two weeks after the guns fell silent. He met with McClellan, trying to prod his young Napoleon into action, met with other generals, and with thousands of wounded soldiers, including both Union and Confederate. His trip was well-documented, and the photos of his visit are among the most famous of the entire war.
The biggest winner of all was President Lincoln, absolutely. He had won a victory in time for the November election, to show that progress in the war was being made. The Republicans kept the Senate, gaining an additional seat, and also the House, although they lost 27 seats. Despite inflation, new taxes, a longer and deadlier war than expected, and a midterm election, Lincoln had pulled out a victory of his own.
Lincoln, the master politician, turned Antietam into a political windfall. He used the victory as a cover to issue the Emancipation Proclamation, redefining the purpose of the war and turning it into a moral struggle, not a cultural one. With one victory, he showed Congress and the voters that he had control over how the war would progress and what it was about. Moreover, the English Parliament dropped any discussion of bringing the combatants together for negotiations.
What had seemed just a few weeks before like the biggest crisis in the existence of the country up to that time was resolved by a president who chose the best man available for the predicament at hand, not necessarily the one he got along with or liked best or could manipulate: a far cry from what passes for executive decision making these days. Lincoln showed by his decision how to keep one’s eyes on the prize. This is a lesson numerous hospital administrators I know could learn. Lincoln was the greatest President, and his management of this crisis must forever be regarded as brilliant and exemplary of his genius.
Other winners include all subsequent generations of Americans, because Lincoln used McClellan’s victory to issue the Emancipation Proclamation, the critical first step for redefining what liberty and freedom could mean. The 4 million enslaved Americans were also victors. Although a pure wartime measure, it meant that slavery was on the road to extinction; Allen Nevins has pointed out that within weeks, slaves were leaving their masters’ plantations. The common Federal soldiers were victors. The battle showed that they WERE capable of defeating Massa Robert.
This photograph waw taken by Alexander Gardner., working for Mathew Brady. Lincoln wrote his wife that he was about to sit for the famous photographer with Little Mac: “If we can sit still long enough, which should be no problem for the general.” Lincoln was a sharp, quick-witted man, all right. He was highly critical of McClellan for allowing Lee to get away.
The Dead of Antietam
Mathew Brady exhibited a series of 97 photographs taken immediately after the Battle of Antietam. These images were the first to show the dead bodies of soldiers still on the battlefield. The impact of this exhibit changed how non-combatants viewed war, and indeed, war news reporting, ever since.
"Mr. Brady has done something to bring home to us the terrible reality and earnestness of war. If he has not brought bodies and laid them in our dooryards and along the streets, he has done something very like it." So wrote a correspondent for The New York Times after visiting Mathew Brady's Manhattan gallery in October 1862 to view the famed photographer's latest exhibit, "The Dead of Antietam."
The accompanying photographs are the two best-known Antietam photographs and are immediately recognizable to every Civil War enthusiast. The top image shows Confederate dead at the Dunker Church. The photographer was standing in what is today the Visitors Center Parking Lot. The second, entitled “View in the Field, on the west side of Hagerstown road, after the Battle of Antietam,” shows the dead by a fence in a road that still exists. The ease of modern accessibility to these locations and their banality add to our sense of horror. The 95 others are graphic and disturbing even by modern standards, several of which I used in the past week.
The Times review continued:
"You will see hushed, reverent groups standing around these weird copies of carnage," the review noted, "bending down to look in the pale faces of the dead, chained by the strange spell that dwells in the dead men's eyes."
Harper’s Weekly, the leading news weekly, devoted the center spread of its October 18, 1862, issue to images of the Antietam dead. Although the technology did not yet exist to reproduce actual photographs in newspapers and news weeklies, the periodical published woodcut engravings of eight photos, including six showing the dead.
Challenge: Two photographers Brady hired to document the war produced these images at Antietam. Who were these men who took these incredible photographs that changed war reporting forever?
Matthew Brady decided to move on from studio portraits and cartes-de-visite to document the war, and, with permission from President Lincoln, he organized and self-financed a team of photographers who took thousands of photographs documenting camp life and battlefield scenes. One of these photographers on Brady’s team, Alexander Gardner, took all the photographs featured, and James Gibson assisted.
In 1862, Brady’s exhibit The Dead of Antietam showed the public the first ever photographs of a battlefield before the dead had been removed. The exhibition took place at Brady’s studio on Broadway in New York City. In modern society, we often see live battlefield scenes on television news and movie images of graphic content, and have become somewhat desensitized to the violence of warfare. It is hard for us today to fully comprehend the shocking impression this exhibit made.
Gardner arrived on the battlefield on September 19, 1862, two days after the battle had ended. He photographed the dead and the living who handled their remains, demonstrating without protecting the viewer from the sight, those who had grisly wounds, those who fell over rocks in their final moments, and the bodies bloating under the hot sun.
Gardner and Brady knew they were capturing history with their cameras, but their primary reason for taking battlefield images was that they knew they would sell. Civil War photos and stereo views sold well during and after the war. Their popularity is evidenced by the dozens of original views available today at online auction sites or from antique photograph dealers. Brady’s stereographs and Album Gallery Cards cost 50 cents each during the war. That’s $10.67 in 2020 dollars, putting them in the same general price range as a video or movie today.
These images received extensive media attention. They shocked and fascinated, and saddened those who saw them. And to this day, they remain some of the most graphic images of American war casualties ever published. Unlike the battle images of Vietnam, these images did not create an anti-war backlash. Instead, they convinced the public that the soldiers fighting for their country were indeed brave, and that war was not the glorious spectacle of fairy tales.
The New York Times review conveys the impact of these photos, perhaps as well as the photos themselves:
“The living that throng Broadway care little perhaps for the Dead at Antietam, but we fancy they would jostle less carelessly down the great thoroughfare, saunter less at their ease, were a few dripping bodies, fresh from the field, laid along the pavement. There would be a gathering up of skirts and a careful picking of way; conversation would be less lively, and the general air of pedestrians more subdued. As it is, the dead of the battlefield come up to us very rarely, even in dreams. We see the list in the morning paper at breakfast, but dismiss its recollection with the coffee.”
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References
· Sears Stephen. Landscape Turned Red: The Battle of Antietam, Houghton Mifflin, 1983.
· Rossino, Alexander & Thorp, Gene. The Tale Untwisted: George McClellan and the Discovery of Lee's Lost Orders, September 13, 1862. El Dorado Hills, CA: Savas Beatie.
· Rossino, Alexander. Their Maryland: the Army of Northern Virginia from the Potomac Crossing to Sharpsburg in September 1862. Savas Beatie. 2021.
· Rossino, Alex. Calamity at Frederick: Robert E. Lee, Special Orders No. 191, and Confederate Misfortune on the Road to Antietam. Savas Beattie, 2023.
· Hartwig, D Scott. I Dread the Thought of the Place: The Battle of Antietam and the End of the Maryland Campaign. Johns Hopkins University Press, 2023.
· https://emergingcivilwar.com/2022/02/24/who-lost-the-lost-order/
· https://www.rebellionresearch.com/special-order-191-ruse-of-war-part-1
· https://www.theodysseyonline.com/the-insignificance-of-special-order-191
· Rossino, Alexander B. Reset in Maryland. America’s Civil War Winter 2024 pp 22-31.
· Rossino, Alexander. Lecture: Before September: The Origin of the 1862 Maryland Campaign. Antietam Institute, July 7, 2025.
· https://www.washingtonpost.com/wp-srv/special/artsandliving/civilwar/mcclellan-graphic/
· Marcel D'Aoust. https://www.historynet.com/little-mac-not-dawdle/
· https://www.battlefields.org/learn/civil-war/battles/shepherdstown
· https://www.nytimes.com/1862/10/20/archives/bradys-photographs-pictures-of-the-dead-at-antietam.html
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