Armies Moves to Antietam

After McClellan's capture of South Mountain on the 15th, the fall of Harper's Ferry to Stonewall Jackson on the 15th came just in time to redeem the Union fortunes for the campaign. Lee's Army of Northern Virginia was moving on the 16th to concentrate on Sharpsburg, Maryland, along the banks of the Potomac River. McClellen was already in Sharpsburg with his army. However, he refused to attack. Just days before he had been confident that with Lee's Lost Order telling of the division of his army he could, without a doubt, whip Bobby Lee. But now he lost that confidence. Although he should have known Lee's army was divided, he spent the day reconnoitering instead of pushing forward to attack. This mistake meant that instead of crushing a small part of Lee's army, he would have a hart fight the next day against a unified Confederate army.