The position of the enemy was a very favorable one. It is thus described by General McClellan:
“The masses of his troops were still concealed behind the opposite heights. Their left and centre were upon and in front of the Sharpsburgh and Hagerstown turnpike, hidden by woods and irregularities of the ground; their extreme left resting upon a wooded eminence near the cross roads to the north of J. Miller’s farm: their left resting upon the Potomac. Their line extended south, the right resting upon the hills to the south of Sharpsburgh, near Shaveley’s farm.
“The bridge over the Antietam, described as No. 3, near this point, was strongly covered by riflemen protected by rifle-pits, stone fences, etc., and enfiladed by artillery. The ground in front of this line consisted of undulating hills, their crests in turn commanded by others in the rear. On all favorable points the enemy’s artillery was posted, and their reserves, hidden from view by the hills, on which their line of battle was formed, could manœuvre unobserved by our army, and from the shortness of their line could rapidly reinforce any point threatened by our attack. Their position, stretching across the angle formed by the Potomac and Antietam, their flanks and rear protected by these streams, was one of the strongest to be found in this region of country, which is well adapted to defensive warfare.”
At dawn of the 17th, skirmishing by the Pennsylvania reserves opened the battle for the day. General Hooker’s entire corps was soon engaged. The right of General Pickett’s line, and the left of General Meade’s reserve, opened fire at about the same moment. A battery was pushed forward into the middle of an open field, where some of the deadliest struggles of the bloody battle subsequently took place. For half an hour, the line did not swerve a hair’s-breadth from the right to the left. At the close of the half hour, the enemy began to fall slowly back. Their first receding movement inspired the brave patriots before them. Forward! was the cry; and the whole line moved forward, with a cheer and a rush; while the rebels in full retreat, running over corn-fields, crossing roads and leaping fences, fled before them.
Close upon the footsteps of the foe, passing over the dead and wounded—for these the rebels were compelled to leave in their wake—followed the soldiers of the Union, till at length the enemy disappeared within a wood. Still the Federals pressed on, and gallantly threw themselves upon the cover; when suddenly, from out the gloom and shadow of the trees, was hurled a fearful volley of fire, that caused their undaunted front to waver, bend and break, and sent them, panic-stricken, many yards back. But, almost instantly closing up their shattered lines, they quickly recovered from this temporary confusion; and, though they could not attempt another advance, their ammunition being expended, those who were left to oppose the advancing masses of the enemy retreated in good order, very slowly, their ranks so thinned that, where brigades had been, scarcely regiments remained—little more than a brigade, where had been a whole victorious division. A contemporary account of the battle speaks as follows of the unexpected reverse, there and then encountered by the gallant patriots.
“In ten minutes, the fortune of the day seemed to have changed; it was the rebels now who were advancing, pouring out of the woods in endless lines, sweeping through the corn-field from which their comrades had just fled. Hooker sent in his nearest brigade to meet them, but it could not do the work. He called for another. There was nothing close enough, unless he took it from his right. His right might be in danger if it was weakened, but his centre was already threatened with annihilation. Not hesitating one moment, he sent orders to Doubleday: ‘Give me your best brigade instantly.’
“The best brigade came down the hill to the right on a run, went through the timber in front swept by a storm of shot and bursting shell and crashing limbs, over the open field beyond and straight into the open corn-field, passing as they went the fragments of three brigades shattered by the rebel fire and streaming to the rear. They passed by Hooker, whose eyes lighted as he saw these veteran troops, led by a soldier whom he knew he could trust. ‘I think they will hold it,’ he said.
“General Hartsuff took his troops very steadily, but, now that they were under fire, not hurriedly, up the hill from which the corn-field begins to descend, and formed them on the crest. Not a man who was not in full view—not one who bent before the storm. Firing at first in volleys, they fired then at will with wonderful rapidity and effect. The whole line crowned the hill and stood out darkly against the sky, but lighted and shrouded ever in flame and smoke. They were the Twelfth and Thirteenth Massachusetts and another regiment—old troops all of them.
“There, for half an hour, they held the ridge, unyielding in purpose, exhaustless in courage. There were gaps in the line, but it nowhere bent. Their General was severely wounded, early in the fight, but they fought on. Their supports did not come—they determined to win without them. They began to go down the hill and into the corn; they did not stop to think that their ammunition was nearly gone; they were there to win that field, and they won it. The rebel line for the second time fled through the corn and into the woods. I cannot tell how few of Hartsuff’s brigade were left when the work was done; but it was done. There was no more gallant, determined, heroic fighting, in all this desperate day. General Hartsuff is very severely wounded, but I do not believe he counts his success too dearly purchased.
“The crisis of the fight at this point had arrived. Rickett’s division, vainly endeavoring to advance and exhausted by the effort, had fallen back. Part of Mansfield’s corps was ordered to their relief, but Mansfield’s troops came back again, and their General was mortally wounded. The left nevertheless was too extended to be turned, and too strong to be broken. Rickett sent word he could not advance, but could hold his ground. Doubleday had kept his guns at work on the right, and had finally silenced a rebel battery that for half an hour had poured in a galling enfilading fire along Hooker’s central line. There were woods in front of Doubleday’s hill which the rebels held, but so long as those guns pointed toward them they did not care to attack.