The Battle of Antietam (known as the Battle of Sharpsburg in the South), fought on September 17, 1862, near Sharpsburg, Maryland, part of the Maryland Campaign, was the first major battle in the American Civil War to take place on Northern soil. It was the bloodiest single-day battle in American history, with over 23,000 casualties, but also has unique significance as the [partial] victory that gave President Abraham Lincoln the confidence to announce his Emancipation Proclamation. The battle is commemorated at Antietam National Battlefield.
Confederate General Robert E. Lee’s Army of Northern Virginia—40,000 men—had entered Maryland following their recent victory at Second Bull Run. Lee’s strategy was to seek new supplies and fresh men (from the border, slave-holding state of Maryland, which had considerable pockets of Confederate sympathies) and to impact public opinion in the North.
While Major General George B. McClellan’s 87,000-man Army of the Potomac was moving to intercept Lee, a Union soldier discovered a mislaid copy of the detailed battle plans of Lee’s army—General Order number 191—wrapped around three cigars. The order indicated that Lee had divided his army and dispersed portions geographically (to Harpers Ferry, West Virginia, and Hagerstown, Maryland), thus making each subject to isolation and defeat in detail if McClellan could move quickly enough. McClellan waited about 18 hours before deciding to take advantage of this intelligence and position his forces based on it, thus endangering a golden opportunity to defeat Lee decisively.
There were two significant engagements in the Maryland campaign prior to the major battle of Antietam: Lieutenant General Stonewall Jackson’s capture of Harpers Ferry and McClellan’s assault through the Blue Ridge Mountains in the Battle of South Mountain.
Near of the town of Sharpsburg, Lee deployed his army behind Antietam Creek along a low ridge. Jackson defended the left (north) flank, anchored on the Potomac River, James Longstreet the right (south) flank, anchored on the Antietam. This was a precarious position because the Confederate rear was blocked by the Potomac River and only a single ford was available should retreat be necessary. Although McClellan arrived in the area on September 16, his trademark caution delayed his attack on Lee, which gave the Confederates more time to prepare defensive positions and allowed Longstreet’s corps to arrive from Hagerstown and Jackson’s corps, minus A.P. Hill’s division, to arrive from Harpers Ferry.
On the evening of September 16, McClellan ordered the I Corps under Maj. Gen. Joseph Hooker to cross Antietam Creek and probe the enemy positions. George G. Meade’s division of regulars cautiously attacked Confederates under John B. Hood near the East Woods. After darkness, artillery fire continued as McClellan continued to position his troops. The skirmish in the East Woods served to signal McClellan’s intentions to Robert E. Lee, who prepared his defenses accordingly.
The battle the next day can be viewed as essentially three separate, mostly uncoordinated battles: morning in the northern end of the battlefield, mid-day in the center, and afternoon in the south. This lack of coordination and concentration of McClellan’s forces almost completely nullified the two-to-one advantage the Union enjoyed and allowed Lee to shift his defensive forces to parry each thrust.
The battle opened at dawn on September 17 with an attack down the Hagerstown Turnpike by the Union I Corps. Hooker’s artillery opened fire on Jackson’s men across a cornfield on the Miller farm. The artillery and rifle fire from both sides acted like a scythe, cutting down all the cornstalks and over 8,000 men on both sides. Hooker’s report stated:
… 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 [Confederates] slain lay in rows precisely as they had stood in their ranks a few moments before
According to some accounts, possession of the cornfield changed hands up to fifteen times that morning.
Jackson’s defense was reinforced at 7 a.m. by John B. Hood’s division, whose Texans attacked with particular ferocity because they were forced to interrupt the first hot breakfast they had had in days. They in turn were driven partially back when the Union XII Corps under Maj. Gen. Joseph K. Mansfield counterattacked. Mansfield was killed in the initial attack and his corps came under strong fire from around the Dunker Church. Soon after, Hooker was wounded in the foot and removed from the field.
In an effort to turn the Confederate left flank and relieve the pressure on Mansfield’s men, Maj. Gen. John Sedgwick’s division of the II Corps (under Maj. Gen. Edwin V. Sumner) advanced into the West Woods. Sumner recklessly launched the division attack en masse without adequate reconnaissance. They were assaulted from three sides, and in less then half an hour their momentum was stopped with over 2,200 casualties.
The morning phase ground to a halt with casualties over 12,000, including two Union corps commanders.
In the center, another division of Sumner’s corps, under Maj. Gen. William H. French, moved to support Sedgwick, but took the wrong road and headed south. They encountered the division of Confederate Maj. Gen. D. H. Hill defending a ridge in a sunken road worn down by years of wagon traffic, which formed a natural trench. In a series of four assaults over three hours, French’s men, along with the division of Maj. Gen. Israel B. Richardson, battered Hill’s improvised breastworks. Finally the Union was able to get enfilade fire into the Confederate line, forcing it to fall back. The carnage from 9:30 a.m. to 1:00 p.m. on the sunken road gave it the name Bloody Lane, leaving about 5,500 casualties along the 800-yard road.
Richardson drove the Confederates from the hills south of Bloody Lane, wrecking the center of Lee’s line. Maj. Gen. William B. Franklin of the VI Corps was ready to exploit this breakthrough, but Sumner, the senior corps commander, ordered him not to advance. Franklin appealed to McClellan, who backed Sumner’s decision.
Another reserve unit was near the center, the V Corps under Maj. Gen. Fitz John Porter. Maj. Gen. George Sykes, commanding his 2nd division, also recommended an attack in the center later in the day, which intrigued McClellan. However, Porter is said to have told McClellan, “Remember, General, I command the last reserve of the last Army of the Republic.”; McClellan demurred and another opportunity was lost.
Southeast of the town on the Union left, Maj. Gen. Ambrose Burnside’s IX Corps had been stalled since 9:30 a.m. in attempts to cross a bridge over Antietam Creek. His orders had been to create a diversion in support of the main attack (Hooker’s, on the right), exploiting it if possible. Due to inadequate scouting, he was unaware that several shallow points existed nearby for fording infantry, and over three hours and three assaults were wasted at the bridge, later named Burnside’s Bridge. Sharpshooters from Georgia in the division of David R. Jones were the primary impediment to Burnside’s progress. His corps finally crossed the creek by 1:00 p.m., but took another two hours to regroup before advancing west towards Sharpsburg and threatening to envelop Lee’s right flank. However, by this late hour A.P. Hill’s Light Division had just completed a rapid forced march from Harpers Ferry and was able to repulse Burnside
The battle was over by 5:30 p.m. Losses for the day were heavy on both sides. The Union had 12,410 casualties with about 2,100 dead. Confederate casualties were 10,700 with about 2,700 dead. On the evening of September 18, after a truce for both sides to recover their wounded, Lee’s forces began withdrawing across the Potomac to return to Virginia.
Although a tactical draw, the Battle of Antietam is considered a strategic Union victory and a turning point of the war because it forced the end of Lee’s invasion of the North and it allowed President Lincoln to issue the Emancipation Proclamation, taking effect on January 1, 1863. Although Lincoln had intended to do so earlier, he was advised by his Cabinet to make this announcement after a Union victory to avoid the perception that it was issued out of desperation. The winning of the Battle of Antietam also may have dissuaded the governments of France and Britain from recognizing the Confederacy; some suspected they were planning to do so in the aftermath of another Union defeat