The Battle of Antietam

The Battle of Antietam in September 1862 turned back the first major Confederate invasion of the North in the Civil War. And it gave President Abraham Lincoln enough of a military victory to go forward with the Emancipation Proclamation.

The battle was shockingly violent, with casualties so high on both sides that it forever became known as "The Bloodiest Day in American History." Men who survived the entire Civil War would later look back at Antietam as the most intense combat they had endured.

The battle also became ingrained in the minds of Americans because an enterprising photographer, Alexander Gardner, visited the battlefield within days of the fighting. His images of dead soldiers still on the field were like nothing anyone had seen before. The photographs shocked visitors when they were displayed at the New York City gallery of Gardner's employer, Mathew Brady. 

The Confederate Invasion of Maryland

Lithograph of fighting at the Battle of Antietam
The Battle of Antietam became legendary for its intense combat. Library of Congress

After a summer of defeats in Virginia in the summer of 1862, the Union Army was demoralized in its camps near Washington, D.C. at the beginning of September.

On the Confederate side, General Robert E. Lee was hoping to strike a decisive blow by invading the North. Lee's plan was to strike into Pennsylvania, imperiling the city of Washington and forcing an end to the war.

The Confederate Army began crossing the Potomac on September 4, and within a few days had entered Frederick, a town in western Maryland. The citizens of the town stared at the Confederates as they passed through, hardly extending the warm welcome Lee had hoped to receive in Maryland.

Lee split up his forces, sending part of the Army of Northern Virginia to capture the town of Harpers Ferry and its federal arsenal (which had been the site of John Brown's raid three years earlier).

McClellan Moved to Confront Lee

Union forces under the command of General George McClellan began moving northwest from the area of Washington, D.C., essentially chasing the Confederates.

At one point the Union troops camped in a field where the Confederates had camped days earlier. In an astounding stroke of luck, a copy of Lee's orders detailing how his forces were divided was discovered by a Union sergeant and taken to the high command.

General McClellan possessed invaluable intelligence, the precise locations of Lee's scattered forces. But McClellan, whose fatal flaw was an excess of caution, did not fully capitalize on that precious information.

McClellan continued in his pursuit of Lee, who began consolidating his forces and preparing for a major battle.

Battle of South Mountain

On September 14, 1862, the Battle of South Mountain, a struggle for mountain passes which led into western Maryland, was fought. The Union forces finally dislodged the Confederates, who retreated back into a region of farmland between South Mountain and the Potomac River.

At first it appeared to Union officers that the Battle of South Mountain might have been the big conflict they were anticipating. Only when they realized that Lee had been pushed back, but not defeated, that a much larger battle was yet to come.

Lee arranged his forces in the vicinity of Sharpsburg, a small Maryland farming village near the Antietam Creek.

On September 16 both armies took up positions near Sharpsburg and prepared for battle.

On the Union side, General McClellan had more than 80,000 men under his command. On the Confederate side, General Lee's army had been diminished by straggling and desertion on the Maryland campaign, and numbered approximately 50,000 men.

As the troops settled into their camps on the night of September 16, 1862, it seemed clear that a major battle would be fought the next day.

Morning Slaughter in a Maryland Cornfield

The Dunker Church at Antietam
The attack in the cornfield at Antietam focused on a small church. Photograph by Alexander Gardner/Library of Congress

The action on September 17, 1862, played out like three separate battles, with major action happening in distinct areas at different parts of the day.

The beginning of the Battle of Antietam, in the early morning, consisted of a stunningly violent clash in a cornfield.

Soon after daybreak, Confederates troops began to see lines of Union soldiers advancing toward them. The Confederates were positioned among rows of corn. Men on both sides opened fire, and for the next three hours the armies battled back and forth across the cornfield.

Thousands of men fired volleys of rifles. Batteries of artillery from both sides raked the cornfield with grapeshot. Men fell, wounded or dead, in great numbers, but the fighting continued. The violent surges back and forth across the cornfield became legendary. 

For much of the morning the fighting seemed to focus on the ground surrounding a small white country church erected by a local German pacifist sect called the Dunkers.

General Joseph Hooker Was Carried From the Field

The Union commander who had led that morning's attack, Major General Joseph Hooker, was shot in the foot while on his horse. He was carried from the field.

Hooker recovered and later described the scene:

"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 precisely as they had stood in their ranks a few moments before.

"It was never my fortune to witness a more bloody, dismal battle-field."

By late morning the slaughter in the cornfield came to an end, but action in other parts of the battlefield was beginning to intensify.

Heroic Charge Toward a Sunken Road

The sunken road at Antietam
The Sunken Road at Antietam. Photograph by Alexander Gardner/Library of Congress

The second phase of the Battle of Antietam was an attack on the center of the Confederate line.

The Confederates had found a natural defensive position, a narrow road used by farm wagons which had become sunken from wagon wheels and erosion caused by rain. The obscure sunken road would become famous as "Bloody Lane" by the end of the day.

Approaching five brigades of Confederates positioned in this natural trench, Union troops marched into a withering fire. Observers said the troops advanced across open fields "as if on parade."

The shooting from the sunken road stopped the advance, but more Union troops came up behind those who had fallen.

The Irish Brigade Charged the Sunken Road

Eventually the Union attack succeeded, following a gallant charge by the famed Irish Brigade, regiments of Irish immigrants from New York and Massachusetts. Advancing under a green flag with a golden harp on it, the Irish fought their way to the sunken road and unleashed a furious volley of fire at the Confederate defenders.

The sunken road, now filled with Confederate corpses, was finally overtaken by Union troops. One soldier, shocked at the carnage, said the bodies in the sunken road were so thick that a man could have walked on them as far as he could see without touching the ground.

With elements of the Union Army advancing past the sunken road, the center of the Confederate line had been breached and Lee's entire army was now in peril. But Lee reacted quickly, sending reserves into the line, and the Union attack was halted in that part of the field.

To the south, another Union attack began.

Battle of the Burnside Bridge

The Burnside Bridge at Antietam in 1862
The Burnside Bridge at Antietam, which was named for Union General Ambrose Burnside. Photograph by Alexander Gardner/Library of Congress

The third and final phase of the Battle of Antietam took place at the southern end of the battlefield, as Union forces led by General Ambrose Burnside charged a narrow stone bridge crossing the Antietam Creek.

The attack at the bridge was actually unnecessary, as nearby fords would have allowed Burnside's troops to simply wade across the Antietam Creek. But, operating without knowledge of the fords, Burnside focused on the bridge, which was known locally as the "lower bridge," as it was the southernmost of several bridges crossing the creek.

On the western side of the creek, a brigade of Confederate soldiers from Georgia positioned themselves on bluffs overlooking the bridge. From this perfect defensive position the Georgians were able to hold off the Union assault on the bridge for hours.

A heroic charge by troops from New York and Pennsylvania finally took the bridge in the early afternoon. But once across the creek, Burnside hesitated and didn't press his attack forward.

Union Troops Advanced, Were Met By Confederate Reinforcements

By the end of the day, Burnside's troops had approached the town of Sharpsburg, and if they continued it was possible that his men could have cut off Lee's line of retreat across the Potomac River into Virginia.

With amazing luck, part of Lee's army suddenly arrived on the field, having marched from their earlier action at Harpers Ferry. They managed to stop Burnside's advance.

As the day came to an end, the two armies faced each other across fields covered with thousands of dead and dying men. Many thousands of wounded were carried to makeshift field hospitals.

The casualties were stunning. It was estimated that 23,000 men had been killed or wounded that day at Antietam.

The following morning both armies skirmished slightly, but McClellan, with his usual caution, did not press the attack. That night Lee began evacuating his army, retreating across the Potomac River back into Virginia.

Profound Consequences of Antietam

President Lincoln and General McClellan at Antietam
President Lincoln and General McClellan meeting at Antietam. Photograph by Alexander Gardner/Library of Congress

The Battle of Antietam was a shock to the nation, as the casualties were so enormous. The epic struggle in western Maryland still stands as the bloodiest day in American history.

Citizens in both the North and South pored over newspapers, anxiously reading casualty lists. In Brooklyn, the poet Walt Whitman anxiously awaited word of his brother George, who had survived unscathed in a New York regiment which attacked the lower bridge. In Irish neighborhoods of New York families began to hear sad news about the fate of many Irish Brigade soldiers who died charging the sunken road. And similar scenes were played out from Maine to Texas.

In the White House, Abraham Lincoln decided that the Union had gained the victory he needed to announce his Emancipation Proclamation.

The Carnage in Western Maryland Resonated in European Capitals

When word of the great battle reached Europe, political leaders in Britain who may have been thinking about offering support to the Confederacy gave up on that idea.

In October 1862, Lincoln traveled from Washington to western Maryland and toured the battlefield. He met with General George McClellan, and was, as usual, troubled by McClellan's attitude. The commanding general seemed to manufacture countless excuses for not crossing the Potomac and battling Lee again. Lincoln had simply lost all confidence in McClellan.

When it was politically convenient, after the Congressional elections in November, Lincoln fired McClellan, and appointed General Ambrose Burnside to replace him as commander of the Army of the Potomac.

Lincoln also went forward with his plan to sign the Emancipation Proclamation, which he did on January 1, 1863.

Photographs of Antietam Became Iconic

A month after the battle, photographs taken at Antietam by Alexander Gardner, who worked for the photography studio of Matthew Brady, went on display at Brady's gallery in New York City. Gardner's photographs had been taken in the days following the battle, and many of them portrayed soldiers who had perished in the astounding violence of Antietam.

The photos were a sensation, and were written about in the New York Times.

The newspaper said about Brady's display of the photographs of the dead at Antietam: "If he has not brought bodies and laid them in our dooryards and along the streets, he has done something very like it."

What Gardner did was something very novel. He was not the first photographer to take his cumbersome camera equipment to war. But the pioneer of war photography, Britain's Roger Fenton, had spent his time photographing the Crimean War focusing on portraits of officers in dress uniforms and antiseptic views of landscapes. Gardner, by getting to Antietam before the bodies were buried, had captured the gruesome nature of war with his camera.

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McNamara, Robert. "The Battle of Antietam." ThoughtCo, Oct. 29, 2020, McNamara, Robert. (2020, October 29). The Battle of Antietam. Retrieved from McNamara, Robert. "The Battle of Antietam." ThoughtCo. (accessed March 20, 2023).