Thanks to his foreknowledge of Lee’s plans—and, incidentally, thanks to Dad and Battle Jimmie—McClellan had been able to take advantage of Lee’s moment of comparative weakness by forcing battle upon him before Stonewall Jackson’s force could return from the raid on Harper’s Ferry.
Thanks, also, to a delay that has never been explained, McClellan had held off from the attack long enough to let Jackson’s vanguard of ten thousand men join Lee.
Still, the bulk of Jackson’s soldiers—the flower of the Southern host—were still absent when the battle was waged. Jackson, too, whose presence and whose counsels at such a moment would have been worth more than fifty thousand additional men, was still absent at Harper’s Ferry.
Lee was thus coerced by McClellan into giving battle, with his ablest leader and his best fighters far away.
So much for the historic carelessness of the Confederate major-general, D. H. Hill, in losing an all-important paper on the way from Frederick; a carelessness that did untold harm to his cause; and that perhaps might have done far more had McClellan seized all his opportunities instead of merely part of them.
Yet, as historians agree, the finding of the lost paper, and its falling into McClellan’s hands, turned the whole tide of the invasion and changed Lee’s most brilliant campaign into a costly failure. A failure that smote the Confederacy a well-nigh mortal blow on the bare heart.
On the morning of the seventeenth Hooker’s corps was entrenched on the far side of the Antietam, the creek between him and the main Army of the Potomac. On the preceding afternoon, at McClellan’s orders, Fighting Joe had crossed one of the creek’s four stone bridges, defeated a Confederate detachment under Hood, and had seized on a position.
Now, on the seventeenth, Hooker received further orders to attack the Confederate line, engaging it closely; while the bulk of the main army should cross the creek under cover of the fighting and throw itself on the Confederates.
The plan met with only fair success. General Mansfield was killed early in the action. Hooker was wounded.
The embattled Confederates stood firm as a rock; and all day long, at close quarters, the mutual slaughter raged.