What Is the Battle of Antietam? - Facts, Summary & Significance

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  • 0:03 1862 Turning Tides
  • 2:10 The Maryland Campaign
  • 4:04 September 17,1862
  • 7:13 Antietam's Aftermath
  • 9:20 Lesson Summary
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Lesson Transcript
Instructor: Daniel Vermilya
Over 23,000 men fell as casualties in the one-day Battle of Antietam, making it the bloodiest day in American history. The Union victory at Antietam resulted in President Abraham Lincoln issuing his Preliminary Emancipation Proclamation on September 22, 1862.

1862 - Turning Tides

The Battle of Antietam was one of the most important events of the American Civil War. Fought on September 17, 1862, Antietam was the bloodiest single-day battle in American history with over 23,000 casualties (men listed as killed, wounded, captured or missing) in roughly 12 hours. The battle ended the Confederate invasion of Maryland in 1862 and resulted in a Union victory. It also led to President Abraham Lincoln issuing the Preliminary Emancipation Proclamation on September 22, 1862.

In 1862, the American Civil War was entering its second year. In February, Union forces began a string of victories that threatened to destroy the young Confederacy. Union forces under Ulysses S. Grant took Forts Henry and Donelson in Tennessee and in April, those same forces defeated Confederate troops at the Battle of Shiloh. In the East, Union forces under the command of Major General George B. McClellan launched an attempt to capture the Confederate capital of Richmond, Virginia.

By the end of July, however, this tide of Union momentum had been slowed. On June 1, Confederate General Robert E. Lee took over the army defending Richmond. Two months later, after a series of bloody battles outside of the capital, Union forces began falling back. Washington lost faith in McClellan, and his army was recalled from Virginia in order to reinforce Major General John Pope's army, which was moving against Richmond by an overland route. Yet, in the last week of August, Lee's army had thoroughly defeated Pope, as well. Momentum was now firmly in the hands of Lee and the Confederates.

The Maryland Campaign

In early September, Robert E. Lee decided to capitalize on his new momentum. On September 5, he began moving his army, the Army of Northern Virginia, across the Potomac River into Maryland. His primary goal was to defeat Union forces on loyal soil, thereby possibly bringing an end to the war and sealing Confederate independence. A battlefield victory in Maryland could also convince England and France to recognize the Confederacy as an independent nation, a move that both countries were hesitant to make unless the Confederacy proved itself on the battlefield.

Additionally, much of the war had been fought on Virginia soil thus far, and moving into Maryland would both allow Lee to feed his men from Maryland farms and harness support for the Confederate cause in that state. Maryland was a 'Border State' in the Civil War (a slave-holding state that stayed in the Union), and ultimately, the Confederacy wanted Maryland to secede and join their cause. By September 9, all of Lee's army was concentrated at Frederick, where he issued orders to split up his forces to capture the small town of Harpers Ferry, where a Union garrison of 12,000 soldiers was threatening the Confederate army.

While Lee's army was invading Maryland, George McClellan was tasked with putting together a Union force to protect Washington and stop Lee. On September 7, after quickly reorganizing a defeated and demoralized army, McClellan began moving into Maryland to stop the Confederate invasion. By the 14th of September, McClellan had caught up with part of Lee's divided force and the Battle of South Mountain was fought, resulting in a Union victory. The next day, another piece of the Confederate army was able to force the surrender of Harper's Ferry, and Lee began to reunite his army at Sharpsburg, Maryland, near Antietam Creek.

September 17, 1862

The Battle of Antietam began early on the morning of September 17, 1862. Union forces of the First and Twelfth Corps were sent across Antietam Creek the day before by McClellan in an attempt to attack the Confederate left flank (the flank is the side of an army or battle line). From 6:00 a.m. to 10:00 a.m., these forces were engaged with Confederates under Major General Thomas 'Stonewall' Jackson in a 24-acre cornfield, now known simply as The Cornfield.

These were the fiercest hours of the battle; over 8,000 casualties fell during this time. As Union General Joseph Hooker later wrote, 'It was never my fortune to witness a more bloody, dismal battlefield.' During the first hour of the fighting in the Cornfield, the slaughter was so intense that one man fell, was killed, or wounded every second. By 10 am, Union forces had taken the Cornfield, but the Confederates remained on the field.

Just as the fighting in the now-infamous Cornfield was winding down, the Union Second Corps, commanded by Major General Edwin V. Sumner, began moving onto the field. One division of the corps pushed due west into an area known as the West Woods; in this woodlot, these 5,000 Union soldiers were hit by a severe flank attack, losing almost 50% of their strength in half an hour.

While disaster struck in the West Woods, the other two divisions of the Second Corps assaulted an old sunken farm road in the middle of the battlefield, now known as Bloody Lane. From 10:00 a.m. until 1:00 p.m., Union forces struggled to take this position and thousands more were killed, wounded, or missing. By 1:00 p.m., Union forces had taken the road, breaking a hole in the Confederate lines. However, because of exhaustion and heavy casualties, these Union troops were not able to advance any further. By the early afternoon hours of September 17, about 17,000 Union and Confederate soldiers had fallen as casualties at Antietam.

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