BACKGROUND
The Battle of Antietam, fought on 17 September 1862, between Confederate Gen. Robert E. Lee's Army of Northern Virginia and Union Gen. George B. McClellan's Army of the Potomac, remains one of the most significant battles of the American Civil War. It was the first major engagement in the Eastern Theater of the war to take place on Union soil and resulted in the bloodiest single day in American history, with a combined total of 22,726 casualties. Although the Union emerged victorious, the battle was somewhat inconclusive from a tactical standpoint, and the Confederates were able to withdraw their forces back to Virginia. However, the battle's outcome had significant political ramifications, as President Abraham Lincoln gained the confidence to issue the Emancipation Proclamation, declaring all slaves within Confederate territory to be "forever free."

In 2019's The Cambridge History of the American Civil War, historian D. Scott Hartwig writes of the battle's one-day carnage "It was the single deadliest day in the war. Union losses totaled 12,410, including 2,108 killed. The Confederates reported their loss as 10,291, with 1,567 dead, but many of their casualty returns were inaccurate and some units' losses were not reported at all. Their actual loss amy have been as high as Union losses. casualties in some units were frightful. The 27th Georgia, for example, carried 400 men into action and mustered only thirty-seven on the morning of September 18." (Sheehan-Dean 2019, 161)

Despite the southern leadership's assumptions that Maryland would welcome the Confederate forces warmly, pro-Union sentiment was winning out, especially in the western parts of the state. Civilians generally hid inside their houses as Lee's army passed through their towns, or watched in cold silence, while the Army of the Potomac was cheered and encouraged. This contextualizes the atmosphere surrounding the engagement and highlights the social and political divisions existing within the country at the time.The logistical reasons behind Lee's invasion of Maryland also played a significant role. Northern Virginia's farms had been stripped bare of food, and the Confederate army needed to find resources elsewhere. Additionally, some Confederate politicians believed that a victory on Union soil could increase the prospect of foreign recognition and financial support from the United Kingdom and France. Although there is no evidence that Lee thought the Confederacy should base its military plans on this possibility, the notion of foreign intervention was widely debated during the period.

In the lead up to the Battle of Antietam, Maj. Gen. George B. McClellan's Army of the Potomac was moving to intercept Lee. Two Union soldiers discovered a mislaid copy of Lee's detailed battle plans—Special Order 191—wrapped around three cigars. The order indicated that Lee had divided his army and dispersed portions geographically, thus making each subject to isolation and defeat if McClellan could move quickly enough. McClellan waited about 18 hours before deciding to take advantage of this intelligence and reposition his forces, thus squandering an opportunity to defeat Lee decisively. This lapse in judgment and failure to pursue the enemy aggressively highlights McClellan's cautious approach to battle and has been a subject of historical debate and criticism.

Two significant engagements occurred during the Maryland campaign prior to the major battle of Antietam. Maj. Gen. Thomas J. "Stonewall" Jackson's capture of Harpers Ferry resulted in a large portion of General Robert E. Lee's army being absent from the start of the battle of Antietam, attending to the surrender of the Union garrison. McClellan's assault through the Blue Ridge Mountains in the Battle of South Mountain saw the Union advancing enough for Lee to concentrate the remainder of his army at Sharpsburg.

THE DAY OF BATTLE
The battle began after McClellan pursued Lee's army into Maryland, and his forces launched attacks against the Confederate Army's defensive positions in Antietam Creek and Sharpsburg. At dawn on September 17, Union Maj. Gen. Joseph Hooker's corps led a fierce assault on Lee's left flank. The battle opened at dawn with an attack by Union I Corps under Joseph Hooker. Hooker's objective was the plateau on which sat the Dunker Church. Hooker had approximately 8,600 men, little more than the 7,700 defenders under Stonewall Jackson, and this slight disparity was more than offset by the Confederates' strong defensive positions.

Brig. Gen. Abner Doubleday's division moved on Hooker's right, Brig. Gen. James B. Ricketts's moved on the left into the East Woods, and Brig. Gen. George G. Meade's Pennsylvania Reserves division deployed in the center and slightly to the rear. Jackson's defense consisted of the divisions under Alexander Lawton and John R. Jones in line from the West Woods, across the Turnpike, and along the southern end of Miller's Cornfield. Four brigades were held in reserve inside the West Woods.

As the first Union men emerged from the North Woods and into the Cornfield, an artillery duel erupted. Confederate fire was from the horse artillery batteries under Jeb Stuart to the west and four batteries under Col. Stephen D. Lee on the high ground across the pike from the Dunker Church to the south. Union return fire was from nine batteries on the ridge behind the North Woods and twenty 20-pounder Parrott rifles, 2 miles east of Antietam Creek. The conflagration caused heavy casualties on both sides and was described by Col. Lee as "artillery Hell."

By midday, the action had shifted to the center of the Confederate line. Maj. Gen. Edwin V. Sumner had accompanied the morning attack of Sedgwick's division, but another of his divisions, under Brig. Gen. William A. French, lost contact with Sumner and Maj. Gen. John Sedgwick and inexplicably headed south. Eager for an opportunity to see combat, French found skirmishers in his path and ordered his men forward. French confronted D.H. Hill's division, commanded by about 2,500 men, less than half the number under French, and three of his five brigades had been torn up during the morning combat. This sector of Longstreet's line was theoretically the weakest. But Hill's men were in a strong defensive position, atop a gradual ridge, in a sunken road worn down by years of wagon traffic, which formed a natural trench. French launched a series of brigade-sized assaults against Hill's improvised breastworks at around 9:30 a.m. The action resulted in a huge loss of life, with French's division suffering 1,750 casualties (of his 5,700 men) in under an hour.

The action moved to the southern end of the battlefield. In the afternoon, Union Maj. Gen. Ambrose Burnside's corps entered the action, capturing a stone bridge over Antietam Creek and advancing against the Confederate right. Burnside had four divisions (12,500 troops) and 50 guns east of Antietam Creek. Facing him was a force that had been greatly depleted by Lee's movement of units to bolster the Confederate left flank. Burnside was strangely passive during preparations for the battle. He was disgruntled that McClellan had abandoned the previous arrangement of "wing" commanders reporting to him. Previously, Burnside had commanded a wing that included both the I and IX Corps, and now he was responsible only for the IX Corps.

Burnside had been instructed to wait for explicit orders before launching his attack, and those orders did not reach him until 10 a.m. But by this time, the divisions of Brig. Gens. David R. Jones and John G. Walker had already been removed. Jones had only about 3,000 men and 12 guns available to meet Burnside. Four thin brigades guarded the ridges near Sharpsburg, primarily a low plateau known as Cemetery Hill. The remaining 400 men—the 2nd and 20th Georgia regiments, under the command of Brig. Gen. Robert Toombs, with two artillery batteries—defended Rohrbach's Bridge, a three-span, 125-foot stone structure that was the southernmost crossing of the Antietam.

It would become known to history as Burnside's Bridge because of the notoriety of the coming battle. Confederate Maj. Gen. A. P. Hill's division arrived from Harpers Ferry and launched a surprise counterattack, driving back Burnside and ending the battle. The bridge was a difficult objective. Burnside launched a series of assaults against the Confederate defenders in an attempt to take the bridge, but they were unsuccessful. Burnside suffered a staggering 1,800 casualties (of his 12,500 men) during the battle.

Although the battle's outcome was somewhat inconclusive, it was a significant turning point in the war in favor of the Union due in large part to its political ramifications. Lincoln's issuance of the Emancipation Proclamation discouraged the British and French governments from recognizing the Confederacy, given their reluctance to appear supportive of slavery. Furthermore, the battle proved that the Union could put up a strong military resistance against the Confederates on their home soil and that the possibility of a Confederate military victory was not an inevitable outcome of the war.

THE DEAD AND DYING
The casualties from the battle were heavy on both sides. Several generals died as a result of the battle, including Maj. Gens. Joseph K. Mansfield and Israel B. Richardson and Brig. Gen. Isaac P. Rodman on the Union side, and Brig. Gens. Lawrence O. Branch and William E. Starke on the Confederate side. Confederate Brig. Gen. George B. Anderson was shot in the ankle during the defense of the Bloody Lane, survived the battle, but later died in October after undergoing an amputation. In Battle Cry of Freedom, historian James McPherson notes that "Nearly 6,000 men lay dead or dying, and another 17,000 wounded groaned in agony or endured in silence. The casualties at Antietam numbered four times the total suffered by American soldiers at the Normandy beaches on June 6, 1944. More than twice as many Americans lost their lives in one day at Sharpsburg as fell in combat in the War of 1812, the Mexican War, and the Spanish-American War combined." (McPherson 2003, 544)

BIBLIOGRAPHY

Catton, Bruce. The Civil War. Boston: Houghton Mifflin Harcourt, 2005.

Catton, Bruce. Bruce Catton: The Army of the Potomac Trilogy: Mr. Lincoln's Army / Glory Road / A Stillness at Appomattox. New York: Library of America, 2022.

Foote, Shelby. The Civil War: A Narrative: Fredericksburg to Meridian. New York: Random House, 2011.

McPherson, James M. Battle Cry of Freedom: The Civil War Era. Oxford: Oxford University Press, 2003.

Sheehan-Dean, Aaron, editor. The Cambridge History of the American Civil War. Cambridge: Cambridge University Press, 2019.