Antietam was a campaign and battle fought in the eastern theater of operations between Union Maj. Gen. George B. McClellan’s Army of the Potomac and Confederate general Robert E. Lee’s Army of Northern Virginia. The failure of Lee’s invasion of Maryland ensured enough of a Northern victory to allow President Abraham Lincoln to issue the preliminary Emancipation Proclamation. Thus, Antietam marked a turning point in the war for the North, as the goal changed from union to union and freedom.
Following his success on the Virginia Peninsula (March-June 1862) and at the Second Battle of Bull Run (August 1862), Lee capitalized on apparent Union demoralization by invading the North. Besides hoping to maintain the strategic initiative by attacking, he sought to achieve a dramatic victory on Union soil that might win the Confederacy diplomatic recognition from England and France. Crossing the Potomac River during the first week of September, he encamped his approximately 40,000 soldiers near Frederick, Maryland, on September 9. Disregarding the Union army, he divided his forces, sending one corps commanded by Thomas J. (Stonewall) Jackson to capture Harpers Ferry and the other under James Longstreet toward Hagerstown. Together, these two operations would stop east-west Union rail traffic. Ultimately, he intended to unite his army near Hagerstown or Boonsboro.
Union general McClellan, a master of military organization and recently appointed to command all forces near Washington, D. C., soon had roughly 75,000 soldiers searching for the Confederate troops. His numerical superiority notwithstanding, McClellan behaved as he always did, with excessive caution, and pursued the enemy slowly. By September 12 he was in the vicinity of Lee’s former campground near Frederick, where his soldiers found a copy of the Confederate operations order. Special Order No. 191 revealed to McClellan the scattered nature of Lee’s deployment, which left him vulnerable to defeat in
Battle of Antietam/Sharpsburg, September 17, 1862 (Library of Congress)
Piecemeal. Within 48 hours, the Union troops had crossed Catoctin Mountain and were threatening to break through the passes at South Mountain.
Meanwhile, the II Corps under Gen. Jackson had surrounded Harpers Ferry and commenced a heavy bombardment on September 14. Jackson was under strict orders to capture this strategic post no later than the 15th and then march directly back to reinforce the main body concentrating at Sharpsburg. That very morning heavy Confederate shelling of the Federal positions forced the Union commander to surrender. The garrison surrendered 10,000 men, 13,000 small arms, and 73 cannons. Jackson secured his prisoners and booty, then he hurriedly rejoined Lee’s army to occupy its left flank. The division of Gen. Ambrose P. Hill remained behind at Harpers Ferry and was expected to rendezvous with them later in the afternoon.
Realizing that the enemy was about to split his army, Lee ordered a concentration near the western Maryland town of Sharpsburg. To buy him the time he needed, he directed Maj. Gens. Daniel H. Hill and J. E. B. Stuart to hold the passes on South Mountain. They resisted the Union advance at Crampton, Fox, and Turner’s Gaps, but by noon on September 15 they were withdrawing back to Sharpsburg. With Lee’s army pinned against the Potomac, and much of it still on the road from Harpers Ferry, McClellan failed to capitalize on Confederate disorganization and weakness by attacking immediately. Instead, he wasted the entire next day leisurely deploying his troops in sight of Lee’s rapidly improving command.
Nonetheless, McClellan had conceived an excellent plan: heavily striking both of Lee’s flanks while keeping two complete corps in reserve to either exploit a breakthrough or crush his center if Lee shifted troops to other sectors. The Union attack progressed from north to south. At 6 a. m. McClellan opened with the I Corps (Joseph Hooker) attacking due south on the Hagerstown-Sharps-burg Turnpike. A little over an hour later his XII Corps (Joseph Mansfield) joined the fight. The heaviest fighting took place in sight of a small white building called Dunkard Church in a recently harvested cornfield. Fighting was intense as brigades from Jackson’s, John Bell Hood’s and Richard S. Ewell’s divisions launched fierce counterattacks throughout the morning. By 9 a. m., Maj. Gen. John Sedgwick’s division of II Corps, with the corps commander Edwin V. Sumner in the lead, joined the fight in the cornfield. In response, Lee moved John Walker’s division from the southern portion of the line. Then his and Lafayette McLaws’s divisions struck Sedgwick’s troops, driving them back in disarray. By noon, fighting was all but over on the northern portion of the battlefield, as the Confederates, bloodied but unbowed, had stood their ground.
Sumner’s other two divisions followed the first without guidance or a clear objective. As they crossed Antietam
Creek they diverged from the rest of the corps and drifted south. Wandering over a small rise, they ran into the Confederate commands of Daniel H. Hill and Richard Anderson along a small sunken farm road. The bloody and intense struggle continued as Gen. William French’s division took the brunt of the Southern defenses. A little after noon, Gen. Israel Richardson’s trailing division penetrated the rebel positions, inflicting a withering fire on the retreating defenders. The way was open to Sharpsburg, and McClellan still had Fitz John Porter’s V Corps in reserve. However, he did not take advantage of his opportunity, ignoring pleas from subordinates to commit additional troops.
Gen. Ambrose E. Burnside began IX Corps’s attack on the southern portion of the battle line around 10 a. m. The greatly outnumbered Confederate force, occupying the high ground on the far bank, dominated the Antietam Creek and its stone bridge. Not until 1 P. M. was Samuel Sturgis’s division able to cross the creek. Two hours later, Burnside had two divisions (Orlando Wilcox’s and Isaac Rodman’s) on their way to Sharpsburg. Lee had no more troops at hand, and McClellan appeared to be on the verge of a decisive victory. Burnside, however, failed to secure the rise on his left flank. Just as he was about to enter the town, Maj. Gen. A. P. Hill’s small division, returning from the Harpers Ferry operation, arrived on the ridge. Arrayed on the ridge line, the Confederate troops appeared to confirm McClellan’s worst fears about being outnumbered. The Union attack stalled and then withdrew back toward Antietam Creek.
The battle reflected badly on Union leadership: McClellan had Lee’s army within his grasp but failed, despite superior resources, to move forward decisively and crush him. Lee remained defiant on September 18, and the Union commander did not use his several fresh corps to finish him off. On the next day, the Southerners withdrew across the Potomac, at the only ford available, without an effective Union pursuit. President Abraham Lincoln, disgusted by McClellan’s inability to destroy the Army of Northern Virginia, relieved him of command in November.
This battle was the bloodiest single day in the Civil War with more than 12,000 Union and almost 14,000 Confederate soldiers killed and wounded. It was one of the first photographed battlefields, and its horrific pictures created shock and dismay among civilians. Nonetheless, the battle granted Lincoln the military pretext he sought to announce his Emancipation Proclamation. This changed the focus of the war from preserving the Union to expanding human freedom and thus discouraged Europeans from entering the conflict.
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Further reading: Ted Ballard, Battle of Antietam (Washington, D. C.: Center of Military History, U. S. Army, 2006); Larry Hama, The Bloodie. st Day: Battle of Antie-tam (Oxford: Osprey, 2006); Donald R. Jermann, The Lost Order (Gretna, La.: Pelican Pub. Co., 2006); James M. McPherson, Crossroads of Freedom, Antietam 1862: The Battle That Changed the Course of Civil War History (New York: Oxford University Press, 2000); Stephen Sears, Landscape Turned Red: The Battle of Antietam (New Haven, Conn.: Ticknor & Fields, 1983); Richard Wheeler, Lee's Terrible Swift Sword: From Antietam to Chancellorsville (Edison, N. J.: Castle Books, 2006).
—Stephen A. Bourque