Maj. Gen. George McClellan’s final battle as commander of the Army of the Potomac was Antietam or as Southerners call it, Sharpsburg. The bloodiest single day battle in American history, Antietam is considered a tactical draw, even though the Union Army held the field while Lee’s Army of Northern Virginia retreated back across the Potomac into the safety of Virginia.
After the debacle of the Seven Days Battles, McClellan had withdrawn his huge army south to the James River where it was under the guns of the Union Navy. In August the bulk of McClellan’s command was transferred to the Army of Virginia, commanded by Maj. Gen. John Pope. Almost immediately Pope was engaged by Lee in a series of battles culminating in his defeat at Second Manassas or Bull Run.
After Pope’s defeat, Lincoln reluctantly returned McClellan to Washington where he combined both his force on the Peninsula and Pope’s shattered army into a strengthened Army of the Potomac. Lincoln told his aid John Hay, “We must use what tools we have. There is no man in the Army who can man these fortifications and lick these troops of ours into shape half as well as he. If he can’t fight himself, he excels in making others ready to fight.”
Meanwhile, Robert E. Lee shorn of any adversaries (or so he thought) crossed the Potomac and invaded Maryland on September 2nd. So began the great chase North. The two forces met at Harpers Ferry which Stonewall Jackson masterfully captured on September 15th. Another wing of Lee’s army fought pitched battles were fought on September 14 for possession of the South Mountain passes: Crampton’s, Turner’s, and Fox’s Gaps.
When Lee realized that he was overmatched he ordered his army to withdraw west to Sharpsburg. Meanwhile, an Indiana soldier discovered Robert E. Lee’s orders to his army wrapped around several cigars. McClellan confided to a subordinate, “Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home.”
Unfortunately, many historians believe that McClellan failed to fully exploit the strategic advantage of the intelligence because he was concerned about a possible trap (posited by Maj. Gen. Henry W. Halleck) or gross overestimation of the strength of Lee’s army.
Many historians say that even though McClellan brought a larger army that the Confederates to Antietam, he brought one soldier too many: himself. At Antietam, McClellan fought a piece-meal battle. Rather than ordering a general attack in the morning, the battle unfolded from north to south in a piece-meal fashion. These tactics allowed Lee’s outnumbered forces to move defensive forces to the points of the Union attacks.
McClellan also confined his movements across Antietam Creek the the various bridges that spanned the waterway. He believed that the creek was unfordable, yet units of Richardson’s Division forded it at the center of the battlefield opposite. My own second great grandfather recorded this in a latter affidavit.
In addition, McClellan has been heavily criticized for holding back his reserve force under the command of Maj. Gen. Fitz John Porter. When Col. Francis C. Barlow and 350 men of the 61st and 64th New York saw a weak point in the line and seized a knoll commanding the sunken road. This allowed them to get enfilade fire into the Confederate line, turning it into a deadly trap.
The Confederate line broke and created a massive hole in their defenses but there was no force to follow up and rout the enemy. Porter is said to have told McClellan, “Remember, General, I command the last reserve of the last Army of the Republic.” McClellan took his implied advice and failed to commit his reserves into a battle that might have been won if he had used his forces aggressively.
McClellan failed to make the correct command decisions at Antietam and it cost the Union Army a clear victory and an opportunity to destroy Lee’s army. The destruction of the Army of Northern Virginia would have left Richmond virtually defenseless and with their capital city captured the South would have likely lost the war in 1862.