Battle of Antietam - Aftermath

Aftermath

The battle was over by 5:30 p.m. Losses for the day were heavy on both sides. The Union had 12,401 casualties with 2,108 dead. Confederate casualties were 10,318 with 1,546 dead. This represented 25% of the Federal force and 31% of the Confederate. More Americans died in battle on September 17, 1862, than on any other day in the nation's military history. Several generals died as a result of the battle, including Maj. Gens. Joseph K. Mansfield and Israel B. Richardson and Brig. Gen. Isaac P. Rodman on the Union side (all mortally wounded), and Brig. Gens. Lawrence O. Branch and William E. Starke on the Confederate side (killed). Brigadier General George B. Anderson got shot in the ankle during the defense of the Bloody Lane. He survived the battle wounded but later on in October he died after the inevitable amputation.

On the morning of September 18, Lee's army prepared to defend against a Federal assault that never came. After an improvised truce for both sides to recover and exchange their wounded, Lee's forces began withdrawing across the Potomac that evening to return to Virginia.

President Lincoln was disappointed in McClellan's performance. He believed that McClellan's cautious and poorly coordinated actions in the field had forced the battle to a draw rather than a crippling Confederate defeat. Historian Stephen Sears agrees.

In making his battle against great odds to save the Republic, General McClellan had committed barely 50,000 infantry and artillerymen to the contest. A third of his army did not fire a shot. Even at that, his men repeatedly drove the Army of Northern Virginia to the brink of disaster, feats of valor entirely lost on a commander thinking of little beyond staving off his own defeat.

— Stephen W. Sears, Landscape Turned Red

The president was even more astonished that from September 17 to October 26, despite repeated entreaties from the War Department and the president himself, McClellan declined to pursue Lee across the Potomac, citing shortages of equipment and the fear of overextending his forces. General-in-Chief Henry W. Halleck wrote in his official report, "The long inactivity of so large an army in the face of a defeated foe, and during the most favorable season for rapid movements and a vigorous campaign, was a matter of great disappointment and regret." Lincoln relieved McClellan of his command of the Army of the Potomac on November 7, effectively ending the general's military career.

Some students of history question the designation of "strategic victory" for the Union. After all, McClellan performed poorly in the campaign and the battle itself, and Lee displayed great generalship in holding his own in battle against an army that greatly outnumbered him. Casualties were comparable on both sides, although Lee lost a higher percentage of his army. Lee withdrew from the battlefield first, the technical definition of the tactical loser in a Civil War battle. However, in a strategic sense, despite being a tactical draw, Antietam is considered a turning point of the war and a victory for the Union because it ended Lee's strategic campaign (his first invasion of the North) and it allowed President Lincoln to issue the Emancipation Proclamation on September 22, which took 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 Union victory and Lincoln's proclamation played a considerable role in dissuading 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. When the issue of emancipation was linked to the progress of the war, neither government had the political will to oppose the United States. Historian James M. McPherson summed up the importance of Antietam in his Crossroads of Freedom:

No other campaign and battle in the war had such momentous, multiple consequences as Antietam. In July 1863 the dual Union triumphs at Gettysburg and Vicksburg struck another blow that blunted a renewed Confederate offensive in the East and cut off the western third of the Confederacy from the rest. In September 1864 Sherman's capture of Atlanta reversed another decline in Northern morale and set the stage for the final drive to Union victory. These also were pivotal moments. But they would never have happened if the triple Confederate offensives in Mississippi, Kentucky, and most of all Maryland had not been defeated in the fall of 1862.

— James M. McPherson, Crossroads of Freedom

The battle is commemorated at Antietam National Battlefield.