Battle of Antietam: The Bloodiest Single Day in American Military History

Deborah Hansen Contributor
Battle of Antietam
Read Time: approx. 3:21

Cover Photo: The Battle of Antietam was a battle of the American Civil War, fought on September 17, 1862, between Confederate and Union troops.

On September 17, 1862, one of the most significant—and bloodiest—battles in America’s history was fought on a 24-acre cornfield in Maryland near Antietam Creek. It was the early days of the Civil War, a war initially labeled as one to restore the United States to its “wholeness.”

Not only was the loss of life extremely high for both the Confederate and Union forces, but the outcome also sent shock waves throughout Europe and the rest of the world. The message was clear: “This is not going to be over any time soon and it’s about more than putting the nation back together.”

President Abraham Lincoln, as Commander in Chief, directed his Army’s General, George McClellan, to stop the Confederate Army of Northern Virginia under the direction of Robert E. Lee from marching into Union territory. Such an incursion was thought to be too close to the US capital in Washington, D.C. and would have brought Confederate occupation to Northern territory. Lincoln believed such a threat needed to be stopped at all costs. That cost turned out to be very high for both armies.

Battle of Antietam

Battle of Antietam by Thulstrup. Specifically, the charge of Iron Brigade near the Dunker Church, on the morning of September 17, 1862.

The battle started in the early morning hours of September 17th and for three hours the cornfield changed hands six times, with neither the Union nor the Confederacy being clear winners of the fight. At 9:00 AM, fighting ceased long enough for both sides to regroup and consider their strategy.

The battle resumed quickly after, though, with each side again taking the upper hand for short periods of time. By 10 AM, the human toll had already reached 10,000 soldiers killed or wounded in only 4 hours of fighting. Over the course of the day, at times it appeared the Confederate troops would be successful at encroaching on Federal territory, only to be repulsed with a new wave of Union troops. Badly needed supplies arrived from Harper’s Ferry by southern troops who had marched approximately 15 miles in 8 hours, also giving the Confederates a morale boost. As daylight faded, however, General Lee retreated back into Virginia territory, with General McClellan making the decision not to pursue and destroy the Confederate army.

The battle was over. In twelve hours of fighting, 23,000 men were killed, wounded, or considered missing in action, making this the bloodiest battle in US military history. President Lincoln felt that McLellan should have pursued and destroyed the Confederate army as they retreated across the Potomac back into their own territory. This disagreement led the Commander in Chief to firing McLellan shortly after the battle.

Battle of Antietam

Battle of Antietam: Dead Confederate soldiers from Starke’s Louisiana Brigade, on the Hagerstown Turnpike, north of the Dunker Church. Photograph by Alexander Gardner.

The results of the Battle of Antietam were felt far and wide. Up until this time, Great Britain and France seemed to believe that the Confederacy would win the war, so both countries were close to giving official recognition—followed by aid—to the south as a separate nation. This would have bolstered the South’s strength and position. Both European countries also had a financial stake in the cotton and slave industries, so they had an economic motivation to help the South win the war.

However, the Union’s victory at Antietam changed everything. The bloody battle, with its hour by hour change in “victors,” made it apparent to not only the public in the divided U.S., but also in Europe that this war was going to be a long and difficult one. As a result, both Great Britain and France withdrew their support of the South, along with any hopes of their assistance to the Confederate cause or political future.

It also injected new strength into the political position of the North. Lincoln was able to point to the victory right before the fall elections of 1862, and the results of those elections showed increased support for his insistence that total decimation of the South was necessary to preserve the nation.

Battle of Antietam

Battle of Antietam: A view down the “Bloody Lane” at the Antietam National Battlefield, in northwestern Maryland.

President Lincoln was able to hold Antietam as an important Union victory, and one from which he could issue The Emancipation Proclamation. In this statement, made on January 1, 1863, he vowed to free all slaves living in any territory held by the Confederacy unless the South laid down their arms. The Battle of Antietam became the watershed moment of the Civil War. From that point on, the war became a fight against slavery rather than merely to heal the break between the North and the South.

“It finally determined that the Civil War was not merely a war for reunion but also a war to end human slavery; turned it from a family scrap into an incalculable struggle for human freedom …”  Author B. Catton.


Be sure to sign up for Tag The Flag’s nonpartisan newsletter to have stories like this and more delivered directly your inbox.