McClellan was very cautious, for he believed the Confederates were on his front in overwhelming numbers. It was ascertained that
Lee's army did not number more than 60,000.
McClellan's effective force was 87,000.
McClellan's army was well in hand (Sept. 16), and
Lee's was well posted on the heights near Sharpsburg, on the western side of Antietam Creek, a sluggish stream with few fords, spanned by four stone bridges. On the right of the National line were the corps of
Hooker and Sumner. In the advance, and near the Antietam, General Richardson's division of Sumner's corps was posted. On a line with this was Sykes's (regular) division of Porter's corps. Farther down the stream was
Burnside's corps. In front of Sumner and Hooker were batteries of 24-pounder Parrott guns. Franklin's corps and Couch's division were farther down the valley, and the divisions of Morrell and Humphrey, of Porter's corps, were approaching from Frederick. A detachment of the
signal corps, under Major Myer, was on a spur of South Mountain.
McClellan prudently hesitated to attack, the Confederates put him on the defensive by opening an artillery fire upon the Nationals at dawn (Sept. 16, 1862). He was ready for response in the course of the afternoon, when Hooker crossed the Antietam with a part of his corps, commanded by Generals Ricketts,
Doubleday. Hooker at once attacked the Confederate left, commanded by "Stonewall Jackson," who was soon reinforced by
General Hood. Sumner was directed to send over
Mansfield's corps during the night, and to hold his own in readiness to pass over the next morning. Hooker's first movement was successful. He drove back the Confederates, and his army rested on their arms that night on the ground they had won. Mansfield's corps crossed in the evening, and at dawn (Sept. 17) the contest was renewed by Hooker. It was obstinate and severe. The National batteries on the east side of the creek greatly assisted in driving the Confederates away, with heavy loss, beyond a line of woods. It was at this time, when Hooker advanced, that
Jackson was reinforced. The Confederates swarmed out of the works and fell heavily upon Meade, when
Hooker called upon
Doubleday for help. A brigade under General Hartsuff pressed forward against a heavy storm of missiles, and its leader was severely wounded. Meanwhile Mansfield's corps had been ordered up, and before it became engaged the veteran leader was mortally wounded. The command then devolved on General Williams, who left his division in the care of General Crawford, and the latter seized a piece of woods nearby. Hooker had lost heavily; Doubleday's guns had silenced a Confederate battery; Ricketts was struggling against constantly increasing numbers on his front; and the National line began to waver, when Hooker, in the van, was wounded and taken from the field. Sumner sent Sedgwick to the support of Crawford, and Gordon and Richardson and French bore down upon the Confederates more to the left. The Nationals now held position at the Dunker Church, and seemed about to grasp the palm of victory (for
Hood were falling back), when fresh Confederate troops, under McLaws and Walker, supported by Early, came up. They penetrated the National line and drove it back, when the unflinching Doubleday gave them such a storm of artillery that they, in turn, fell back to their original position. Sedgwick, twice wounded, was carried from the field, and the command of his division devolved on
General O. O. Howard. Generals Crawford and Dana were also wounded. Franklin was sent over to assist the hard-pressed Nationals. Forming on Howard's left, he sent Slocum with his division towards the centre. At the same time General Smith was ordered to retake the ground on which there had been so much fighting, and it was done within fifteen minutes. The Confederates were driven far back. Meanwhile the divisions of French and Richardson had been busy. The former received orders from Sumner to press on and make a diversion in favor of the right. Richardson's division, composed of the brigades of Meagher, Caldwell, and Brooks (who had crossed the Antietam at ten o'clock), gained a good position. The Confederates, reinforced by fresh troops, fought desperately. Finally, Richardson was mortally wounded, and
Gen. W. S. Hancock succeeded him in command, when a charge was made that drove the Confederates in great confusion. Night soon closed the action on the National right and centre. General Meagher had been wounded and carried from the field, when the command of his troops devolved on Colonel Burke. During the fierce strifes of the day Porter's corps, with artillery and Pleasonton's cavalry, had remained on the east side of the stream, as a reserve, until late in the afternoon, when
McClellan sent over some brigades.
On the morning of the 17th the left, under Burnside, engaged in a desperate struggle for the possession of a bridge just below Sharpsburg. That commander had been ordered to cross it and attack the Confederates. It was a difficult task, and Burnside, exposed to a raking fire from the Confederate batteries and an enfilading fire from sharp-shooters, was several times repulsed. Finally, at a little past noon, two regiments charged across the bridge and drove its defenders away. The divisions of
Sturgis, Wilcox, and Rodman, and Scammon's brigade, with four batteries, passed the bridge and drove the Confederates almost to Sharpsburg.
A. P. Hill, with fresh troops, fell upon Burnside's left, mortally wounding General Rodman, and driving the Nationals nearly back to the bridge. Gen. O.
B. Branch, of North Carolina, was also killed in this encounter. The Confederates were checked by National artillery on the eastern side of the stream, and, reserves advancing under Sturgis, there was no further attempt to retake " the Burnside Bridge," as it was called.
Hill came up just in time to save
Lee's army from destruction.
Darkness ended the memorable struggle known as the Battle of Antietam. The losses were very severe.
McClellan reported his losses at 12,460 men, of whom 2,010 were killed. The losses fell heavily upon certain brigades. That of
Duryee retired from the field with not more than twenty men and four colors. Of the brigades of Lawton and Hays, on the Confederate side, more than one-half were lost. On the morning of the 18th both parties seemed more willing to rest than to fight; and that night
Lee and his army withdrew in the darkness, recrossed the Potomac at
Williamsport, and planted eight batteries on the high Virginia bank that menaced pursuers. There had been a very tardy pursuit. At dark on the evening of the 19th, Porter, who was on the left bank of the river, ordered Griffin to cross the stream with two brigades and carry
Lee's batteries. He captured four of the guns. On the next morning (Sept. 20) a part of Porter's division made a reconnaissance in force on the Virginia side, and were assailed by Hill in ambush, who drove them across the Potomac and captured 209 of the Nationals.