September 17, 1862: The Battle of Antietam (Sharpsburg), the bloodiest single day in American history

“Antietam (called Sharpsburg by the South),” writes James McPherson in Battle Cry of Freedom, “was one of the few battles of the war in which both commanders deliberately chose the field and planned their tactics beforehand.” Confederate General Robert E. Lee believed the Federal troops were demoralized and vulnerable after their recent defeat at Second Manassas. Now was the time to strike. Ever cautious, General George McClellan became emboldened when on September 13 a Union soldier found a copy of Lee’s orders of attack wrapped around three cigars a Southern officer had lost in a field near Frederick, Maryland. “Here is a paper,” McClellan told one of his generals, “with which if I cannot whip Bobbie Lee, I will be willing to go home.”

But McClellan believed Lee’s forces to be twice the size they actually were and took two days to arrange his troops. It wasn’t until September 16 that the northern commander had 60,000 men in the field—and another 15,000 six miles away—to stand against Lee’s 25,000 or 30,000. In a letter to his daughters after the battle Brigadier General Alpheus S. Williams captures the apprehension of the Union troops the night before the battle:

At length I got fairly asleep and for two hours and was dead to all sounds or sensations. I shall not, however, soon forget that night; so dark, so obscure, so mysterious, so uncertain, with the occasional rapid volleys of pickets and outposts, the low solemn sound of the command as troops came into position, and withal so sleepy that there was a half-dreamy sensation about it all; but with a certain impression that the morrow was to be great with the future fate of our country. So much responsibility, so much intense future anxiety! and yet I slept as soundly as though nothing was before me.

Brigadier General Alpheus S. Williams
Photograph by Matthew Brady

New York Daily Tribune correspondent George W. Smalley witnessed the battle and published his account three days later. Wiliam Cullen Bryant, editor of the rival New York Evening Post, hailed the account as one of the “best battle pieces in literature.” Smalley paints the encounter in epic proportions:

Fierce and desperate battle between two hundred thousand men has raged since daylight, yet night closes on an uncertain field. It is the greatest fight since Waterloo—all over the field contested with an obstinacy equal even to Waterloo. If not wholly a victory to-night, I believe it is the prelude to a victory to-morrow. But what can be foretold of the future of a fight in which from five in the morning till seven at night the best troops of the continent have fought without decisive result?

A “Maryland maiden” who viewed the battle from a nearby attic window offers a contrasting view when she writes, “On all the distant hills around were the blue uniforms and shining bayonets of our men, and I thought it was the prettiest sight I ever saw in my life.” Eyewitness accounts closer to the fighting tell quite a different story. Here is Major Rufus R. Dawes of the 6th Wisconsin Infantry relating his experience at the center of the battle for David R. Miller’s cornfield, a swath of ground that changed ownership four times during the day:

As we appeared at the edge of the corn, a long line of men in butternut and gray rose up from the ground. Simultaneously, the hostile battle lines opened a tremendous fire upon each other. Men, I can not say fell; they were knocked out of the ranks by dozens. But we jumped over the fence, and pushed on, loading, firing, and shouting as we advanced. There was, on the part of the men, great hysterical excitement, eagerness to go forward, and a reckless disregard for life, of every thing but victory.

Everyone who witnessed the fighting close up expressed horror at the day’s carnage. Smalley notes that “The dead are strewn so thickly that as you ride over [the battlefield] you cannot guide your horse’s steps too carefully.” Dawes laments the “dreadful slaughter” and Williams reports seeing corpses “as thick as autumn leaves along a narrow lane.” A veteran campaigner known to speak his mind, Williams also offers insight into why the deaths and casualties were so great. For one, he finds fault with how some officers directed the order of battle:

The Rebels had been strongly reinforced, and Sumner’s troops, being formed in three lines in close proximity, after his favorite idea, we lost a good deal of our fire without any corresponding benefit or advantage. For instance, the second line, within forty paces of the front, suffered almost as much as the front line, and yet could not fire without hitting our own men. The colonel of a regiment in the second line said he lost sixty men and came off without firing a gun.

On the offensive side, Williams dramatizes how lethally effective an artillery battery can be:

I was near one of our brass twelve-pound Napoleon gun batteries and seeing the Rebel colors appearing over the rolling ground I directed the two left pieces charged with canister to be turned on the point. In the moment the Rebel line appeared and both guns were discharged at short range. Each canister contains several hundred balls. They fell in the very front of the line and all along it apparently, stirring up a dust like a thick cloud. When the dust blew away no regiment and not a living man was to be seen.

By nightfall, at least 3,600 men were dead and well over 17,000 were wounded. McPherson, who estimates that another 2,000 died from their injuries, puts this in perspective:

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.

Both armies stayed in position on September 18. That evening Lee and his troops returned to Virginia.

Also of interest:

• “A Woman’s Recollections of Antietam,” this week’s Story of the Week
• Phil Leigh writes about Lee’s Lost Order on The New York Times Disunion blog 
• Read more about the Battle of Antietam at The Civil War Trust 
• Brooks D. Simpson on “the very vortex of hell,” Second Manassas (The Second Battle of Bull Run), August 28–30, 1862, a previous Reader’s Almanac post 

Related LOA works: The Civil War: The Second Year Told by Those Who Lived It (contains more than 60 pages on Antietam, including eyewitness accounts by George W. Smalley, Rufus R. Dawnes, Alpheus S. Williams, and many others)