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Battle of Antietam


The Battle of Antietam, also known as the Battle of Sharpsburg, changed the course of the American Civil War. Fought on September 17, 1862, General George B. McClellan’s Army of the Potomac launched a series of assaults against General Robert E. Lee’s Army of Northern Virginia along Antietam Creek near the Maryland village of Sharpsburg. The soldiers in both armies believed that the destiny of their respective nations rested on the outcome of this battle and fought as if there would be no tomorrow. For many men, there was no tomorrow. The two sides combined suffered an estimated 23,000 casualties, making this horrifying fight the bloodiest single day in American history. Most on both sides expected the battle to resume on the 18th. Despite being heavily outnumbered, Lee stayed in position, but McClellan did not renew the attack. That night the Confederate commander ordered his troops back to Virginia, effectively ending Lee’s first invasion of the North. Although the Battle of Antietam ended in a tactical draw, it emerged as a strategic Union victory, frustrating Confederate hopes for European recognition, raising Northern morale, and precipitating President Abraham Lincoln’s Emancipation Proclamation.

When General Robert E. Lee’s Army of Northern Virginia crossed the Potomac River into Maryland in September 1862, the Confederacy appeared to be on the brink of victory. Southern counteroffensives that summer had turned the war around for the Confederacy. If Lee’s first invasion of the North succeeded, European recognition of the Confederate States of America looked very likely. The Army of Northern Virginia had been fighting or marching almost without cessation for ten weeks, but there was no time for rest now. Although Lee had launched the invasion with 55,000 men, many troops had dropped out of the ranks due to stress, exhaustion, illness, and other factors. On September 17, some 36,000 men stood ready for battle. Of those who remained, thousands were shoeless, most of their uniforms were in rags, and all of them were hungry, but those very same men were hardened warriors, confident and determined to achieve a war-winning victory. They had supreme faith in their commander and held a strong defensive position with both flanks anchored on water. Robert E. Lee would make his stand on the high ground east of the Maryland village of Sharpsburg. His only route of retreat was a single ford over the Potomac three miles to the rear, and while that was certainly risky, Lee was not the type of commander who was afraid to take risks.

General Robert E. Lee. (Photo: Wikimedia Commons)

Confederate counteroffensives in the summer of 1862 had erased the momentum that Union forces had been building upon since the start of the year. While many in the North saw Lee’s invasion as a calamity, President Abraham Lincoln viewed it as an opportunity to cripple the enemy army far from its home base. Lincoln called upon General George B. McClellan to go after Lee, and “destroy the rebel army, if possible.” McClellan was not an aggressive fighter, but he had a skill for turning men into soldiers and the Army of the Potomac largely adored him. While recent setbacks had dampened morale, Union troops were reinvigorated by the thunderous welcome that they received in Maryland. The Army of the Potomac was fighting on home turf now and was ready to “smash [the enemy] terribly if they stand,” wrote General Alpheus Williams. McClellan defeated part of Lee’s army at the Battle of South Mountain on September 14, but he didn’t move quickly enough to destroy the Rebel army while it was separated. On the 17th, McClellan had 75,000 effectives to finish the job and break through Lee’s 36,000 (whom McClellan estimated to be 110,000).

General George B. McClellan. (Photo: Wikimedia Commons)

As he so often did, McClellan believed that the enemy outnumbered him, but in reality, it was Lee who had fewer men. By taking advantage of the chosen ground and the experience of his soldiers, Lee would make up for the numerical disadvantage that he faced at Sharpsburg. The Confederates would utilize the cover of small groves, rock outcroppings, stone walls, dips and swells in the rolling terrain, and a sunken road in the center of their line.

While the Confederate position was strong, McClellan put together a battle plan that appeared capable of breaking through it. After crossing Antietam Creek, Maj. Gen. Joseph Hooker’s I Corps and Maj. Gen. Joseph Mansfield’s XII Corps, supported by Maj. Gen. Edwin Sumner’s II Corps, were to deliver the initial attack on the Confederate left. Once these troops were engaged, Maj. Gen. Ambrose Burnside’s IX Corps was expected to fight its way across the Antietam on the Confederate right, creating a distraction to prevent Lee from transferring troops from this sector to reinforce his left, and cut off the enemy’s retreat route to the Potomac Ford. McClellan held four Union divisions and his cavalry in reserve to exploit any breakthrough. If properly coordinated, the Union attacks might have overwhelmed Lee’s smaller force, but McClellan’s plan was not well executed on the day of the pivotal battle.

At dawn on September 17, 1862, “Fighting Joe” Hooker’s troops led the attack against the Confederate left, sweeping south on both sides of the Hagerstown Pike into what would forever after be known as the Cornfield, and through the East Woods. Rebel troops in this area were commanded by General Thomas “Stonewall” Jackson and met the Federals head-on. Major Rufus Dawes of the 6th Wisconsin, a regiment in the famous Iron Brigade, described the action in this sector between 6:00 and 7:00 A.M. “Men, I can not say fell; they were knocked out of the ranks by dozens.” Over the course of the first three hours of the fight, the Blue and the Gray struggled over possession of the thirty-acre cornfield. As both sides launched attacks and counterattacks, the Cornfield changed hands no fewer than six times. Men who fought there agreed that the field was filled with so many dead and wounded that one could walk through the field without ever stepping on the ground.

“In the time I am writing, every stalk of corn in the northern and greater part of the field was cut as closely as with a knife,” wrote General Hooker in his official report, “and the slain lay in rows precisely as they had stood in their ranks a few minutes before. It was never my fortune to witness a more bloody, dismal battlefield.” Painting of the Iron Brigade fighting in the Cornfield by Keith Rocco. (Photo: Warfare History Network)

Lee sent in reinforcements that eventually helped shatter Hooker’s corps before Mansfield’s 12th Corps launched the second wave of the northern assault. Mansfield’s troops penetrated the Confederate lines around the Dunkard Church before being driven back. The third Union wave led by a crack division of Sumner’s 2nd Corps broke through the Rebel line in the West Woods, but was nearly wiped out by a Confederate division that Lee had shifted from his inactive right. After five brutal hours of fighting on the Confederate left, twelve thousand men lay dead and wounded. Historian James McPherson writes, “Five Union and four Confederate divisions were so badly wrecked that they backed off almost as if by mutual consent and did no more serious fighting that day.” General Mansfield was mortally wounded that morning and Hooker was put out of action with a wound. If he had coordinated his attacks, McClellan might have achieved a breakthrough against the Confederate left, but he failed to do so. Because the Union attacks went forward in three stages instead of simultaneously, Lee was able to shift troops from quiet sectors to meet the attacks.

Confederate soldiers killed near the Dunkard Church on the morning of September 17, 1862. According to McPherson, "Within two days of the battle, Northern photographers Alexander Gardner and James Gibson arrived at Antietam and began taking pictures. For the first time in history, the graphic and grisly sight of bloated corpses killed in action could be seen by those who never came close to the battlefield." The two men worked for Mathew Brady, whose studio in New York City exhibited the photographs a month after the battle. (Photo: Wikimedia Commons)

The midday phase of the battle featured more relentless fighting as Union troops slugged it out with Confederate soldiers holding Lee’s center along a half mile of a farm road. It was here “where generations of wagons hauling grain to a mill had worn ruts that eroded the road several feet below ground level,” writes McPherson. This sunken road provided a ready-made trench for the Confederates and would be known ever after as Bloody Lane. Wave after wave of brigade-size Union attacks were beaten back, but at about 1:00 P.M., the Federals finally broke through and cleared Bloody Lane of all surviving unwounded Rebels. According to McPherson, “Four hours of action on this front left a carpet of blue-clad corpses strewn across the fields northeast of the sunken road and a carpet of butternut and gray-clad corpses in the appropriately named Bloody Lane.”

Confederate dead in Bloody Lane after the fighting there at midday September 17, 1862. Photograph by Alexander Gardner. (Photo: Wikimedia Commons)

The Union breakthrough against Lee's center nearly left the Army of Northern Virginia in ruin. “There was no body of Confederate infantry in this part of the field that could have resisted a serious advance,” wrote a Southern officer. Confederate General James Longstreet later said that if 10,000 fresh Union troops had been put in at that moment, the Confederates would have been swept from the field. McClellan had those reinforcements available, but fearing that Lee was massing his own reserves for a counterattack, he decided not to release them. “It would not be prudent to make the attack,” he told General William B. Franklin, who pleaded to be unleashed. The opportunity passed, allowing Lee and Longstreet to patch together a new line along the Hagerstown Pike. McClellan missed his chance, and this sector of the battlefield fell quiet.

McClellan had told General Ambrose Burnside to hold his 9th Corps ready for an early attack across Antietam Creek, but as the dreadful fighting took place on the Confederate left, no orders came. Because of the lack of action on Burnside’s front, Lee was able to shift troops from his right to the left. McClellan’s orders for Burnside to attack arrived at about 10:00 A.M, but Burnside did not move quickly or show much imagination that day. Although Lee only had some 4,000 men to defend against Burnside’s 13,000, the Confederates held high ground commanding the Antietam, with heavy woods and an abandoned quarry overlooking the only bridge across. McPherson points out that although “the thirty-yard wide Antietam was shallow and fordable at several places, Burnside seemed fixated on the bridge.” For some three hours, Union regiments attacked in piecemeal fashion, trying to fight their way across the Rohrbach Bridge, which ever since has been known as Burnside’s Bridge.

“Burnside’s Bridge.” Photograph by Alexander Gardner. (Photo: Library of Congress)

Around 1:00 P.M., a Pennsylvania and New York Regiment attacked directly across the bridge, sustaining losses, clearing out the Confederate defenders, and establishing a bridgehead for the rest of the corps. A delay followed as the lead division had to go back for ammunition. Finally, about 3:00 P.M., Burnside got his whole line moving forward across the hills and fields south of Sharpsburg. The fighting was so intense that “the whole landscape for an instant turned slightly red,” according to one soldier.

The Union attack across “Burnside’s Bridge” around 1:00 P.M. on September 17, 1862. (Photo: Library of Congress)

The sheer weight of Union numbers eventually pushed the Confederates back to the edge of Sharpsburg. By 4:00 P.M., Burnside was poised to cut the road to the only ford over the Potomac. Just as the Confederate right appeared ready to crumble, General A.P. Hill’s division arrived from Harpers Ferry, Virginia (now West Virginia), and crashed into Burnside’s flank. Hill had remained behind to complete the surrender arrangements at Harpers Ferry and got his men on the road by 7:30 A.M. that morning, marching seventeen miles and showing up just in the nick of time to save the day at Sharpsburg.

A.P. Hill leading his division to Sharpsburg in response to an urgent summons from Lee. Hill’s forced march of seventeen miles from Harpers Ferry left hundreds of stragglers strewn along the way, but enough of his troops arrived to save the day. Painting by Dale Gallon. (Photo:

While Burnside’s left had collapsed, the right flank of his attack still threatened to break through a thin Confederate line directly east of Sharpsburg. Once again, McClellan had reserves available that he could have sent in. He seemed ready to commit them until General Fitz-John Porter, commander of the 5th Corps, supposedly said, “Remember, General! I command the last reserve of the last Army of the Republic.” That was all McClellan needed to hear. He still feared that Lee outnumbered him and could launch a devastating counterattack. McClellan refused to give the order, leaving Burnside’s attack unsupported and Lee’s line unbroken.

After a nightmarish day of fighting that few would ever forget, nearly 6,000 men lay dead or dying, and another 17,000 were wounded. More American soldiers died at the Battle of Antietam than died in combat in all the other wars fought by the United States in the nineteenth century combined: the War of 1812, the Mexican-American War, the Spanish-American War, and all the Indian Wars. Across both sides, At least two thousand would die of their wounds. Of those who recovered from their injuries, many would never again walk on two legs or work with two arms. A New Hampshire surgeon wrote, “Who permits it? To see or feel that a power is in existence that can and will hurl masses of men against each other in deadly conflict-slaying each other by the thousands-mangling and deforming their fellow men is almost impossible. But it is so and why we cannot know.”

Confederate soldiers killed on the morning of September 17, 1862, along the fence bordering the Hagerstown Pike just south of the bloody Cornfield. Photograph by Alexander Gardner. (Photo: Wikimedia Commons)

As the sun rose on September 18, 1862, Lee had scarcely 30,000 men alive and unwounded, but he kept his army in position, almost daring McClellan to renew the assault. Most on both sides, including McClellan who had more fresh troops than Lee had men in his whole force, expected the battle to resume. Although he maintained the numerical advantage, McClellan was a constant over-thinker. He still believed that he was outnumbered, concluding, “that the success of an attack on the 18th was not certain,” as he later wrote in his final report almost a year later. The assault was not renewed and both armies remained largely quiet during the 18th. That night, Lee ordered his troops back to Virginia and got clean away. On September 20, McClellan sent several V corps regiments across the Potomac in pursuit, but these troops were easily repulsed by A.P. Hill’s division. General McClellan had driven the enemy back to Virginia, but he failed to destroy Lee’s army.

At no point during the Battle of Antietam did more than 15,000 Union infantry go into action simultaneously, and almost 20,000 of McClellan’s infantry and cavalry never fired a shot at all. Had McClellan’s attacks been better coordinated, the Army of the Potomac might have delivered a mortal blow to the Army of Northern Virginia. Although the Confederates were outnumbered, the desperate courage of the men in the ranks, bolstered by the generalship of Lee and his subordinates, allowed the Southerners to fight the Union to a standstill. “It is beyond all wonder,” wrote a Union officer after the battle, “how such men as the rebel troops can fight on as they do; that, filthy, sick, hungry, and miserable, they should prove such heroes in fight, is past explanation.” Thousands of surviving veterans on both sides would remember Antietam as the worst battle of the war.

Rufus Dawes of the 6th Wisconsin fought in many of the war's deadliest battles: Second Bull Run, Fredericksburg, Gettysburg, the Wilderness, Spotsylvania, the battles around Petersburg, and Antietam. The battle-hardened Westerner later wrote that Antietam "surpassed all in manifest evidence of slaughter." (Photo: Wikimedia Commons)

While the Battle of Antietam ended in a tactical draw, it emerged as an unquestionable strategic Union victory. Some in the North expressed disappointment that Lee’s army had escaped, but overall, the battle and the Confederate retreat boosted morale in the Army of the Potomac and lifted the spirits of the Northern public. The failure of Lee’s invasion gave President Abraham Lincoln the “victory” he had been waiting for to issue the preliminary Emancipation Proclamation, warning Confederate states that unless they returned to the Union by January 1, 1863, their slaves “shall be then, thenceforward, and forever free.” The Battle of Antietam and the Emancipation Proclamation shattered the momentum that had been growing in Britain and in France to recognize Confederate independence. Colonel Walter H. Taylor of Robert E. Lee’s wartime staff described the battle as the decisive “event of the war.” The Confederacy would attain success on later occasions, but never again did Southern armies come so close to victory as they did in September 1862. As James Longstreet wrote twenty years after the war, “At Sharpsburg was sprung the keystone of the arch upon which the Confederate cause rested.”


American Battlefield Trust: Battle of Antietam Facts & Summary.

Crossroads of Freedom: Antietam by James M. McPherson.

The Civil War by Bruce Catton.

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