McClellan, who arrived on the opposite side of Antietam Creek, that
afternoon, had 70,000. Instead of attacking at once, he waited two days,
and thus gave Lee time to gather many thousand stragglers.

[Illustration: ANTIETAM BRIDGE.]

BATTLE OF ANTIETAM OR SHARPSBURG.

Finally, when McClellan had no excuse for further delay, and the enemy
was in fine form, he opened the attack on the morning of the 17th. To
reach Lee the Union commander had to cross the creek, which was spanned
by three bridges, each defended by Confederate batteries.

The first attack was by Hooker on the enemy's left, where he drove
Jackson back, after he had been reinforced by Hood, cleared the woods,
and took possession of the Dunker Church, which stood slightly north of
Sharpsburg. A little way beyond the Confederates made a stand, and,
being reinforced, recovered most of the ground they had lost. General
Mansfield was killed and Hooker received a painful wound in the foot.
When their two corps were retreating in confusion, Sumner arrived,
rallied them, and made a successful stand. Seeing the critical
situation, Lee hurried every available man to that point. This left only
2,500 troops in front of the bridge, where Burnside had 14,000.
McClellan sent repeated orders for him to advance, but he paid no
attention until one o'clock, when he crossed without trouble, and then
remained idle for three more hours. The heights were soon captured, and
a position secured from which the rebel lines could be enfiladed. A.P.
Hill arrived at this juncture from Harper's Ferry with 4,000 men, and
drove Burnside in a panic to the creek. Fighting soon ceased, both sides
too much exhausted to keep up the terrific struggle, the position of the
two armies being much the same as at first.

This fierce battle had wrenched and disorganized both armies, but
McClellan, who had much the larger body, could have destroyed or
captured those in front of him, had he followed the urgent advice of his
officers, and given the enemy no rest. But he decided to await
reinforcements, which arrived to the number of 14,000 that night. Then
he resumed his preparations, and on the morning of the 19th advanced
against the enemy, only to find there was none in front of him.

LEE'S RETREAT.

The retreat of Lee was deliberate. Having accurately gauged the
commander in front of him, he spent all of the 18th in completing his
preparations, and made no move until the next morning. Then,