General George McClellan was at his best strategizing, organizing, and planning. His comfort zone would have been a bureaucratic position buried deep within the war department. Henry Halleck’s position would have suited him just fine. But instead, McClellan was the commander of the Army of the Potomac, readying his troops for battle.
At Antietam, he planned a three-pronged attack.
General Joseph Hooker took the lead and was ordered to establish his base on the right. Sumner, Mansfield, and Franklin were to support Hooker while all the time edging their way toward the center. The center was left mainly to Porter’s artillery.
The fly in the ointment was General Ambrose Burnside. The entire action depended on his taking stone bridge number 3, then turning the rebel’s left flank, thus cutting off any chance of a rebel retreat. McClellan considered giving the over-cautious general more men, but he didn’t have anyone to spare.
His battle plan completed, McClellan moved to his observation post on a high hill overlooking the field. From there, he could watch the action unfold. Then, he could quickly dash to wherever his presence was needed. But most often, his messengers raced off delivering messages for his commanders to change fronts, advance, fallback, or pick up the pace.
McClellan’s all-seeing eye would determine the outcome of the battle. The life and death of nearly 100,000 men hung on the decisions he made—or didn’t make.
Monday, September 16, found the Confederates deployed in force on a crescent-shaped ridge that followed the course of Antietam Creek. The funny thing was they didn’t seem worried about the increasing number of Union troops making their way to the field. They didn’t even seek cover from the Union artillery barrages. The correspondent for the New York Tribune suggested it was an act. The rebels wanted to look stronger than they were.
McClellan assumed Lee was buying time, so he could fortify his position and dig his troops in even deeper. As the day wore on, reinforcements poured in. Stonewall Jackson’s troops left Harper’s Ferry Tuesday and marched all night to reach Antietam in time to join the battle. General A. P. Hill moved his troops down from Harper’s Ferry and arrived just in time to stop Burnside’s attack on Sharpsburg.