Location: The terrain provided excellent cover for infantrymen, with rail and stone fences, outcroppings of limestone, and little hollows and swales. The creek to their front was only a minor barrier, ranging from 60 to 100 feet (18–30 m) in width, and was fordable in places and crossed by three stone bridges each a mile (1.5 km) apart. It was also a precarious position because the Confederate rear was blocked by the Potomac River and only a single crossing point, Boteler's Ford at Shepherdstown, was nearby should retreat be necessary.
Although an immediate Union attack on the morning of September 16 would have had an overwhelming advantage in numbers, McClellan's trademark caution and his belief that Lee had as many as 100,000 men, caused him to delay his attack for a day, in reality Lee had only 18,000. This gave the Confederates more time to prepare defensive positions.
Lack of coordination and concentration of McClellan's (Union) forces almost completely nullified the two-to-one advantage the Union enjoyed and allowed Lee to shift his defensive forces to meet each offensive.
As the first Union men emerged from the North Woods and into the Cornfield, an artillery duel erupted. Confederate fire was from the horse artillery batteries.
Union had four batteries of 20-pounderParrott rifles.
Heavy casualties on both sides and was described by Col. Lee as "artillery Hell.".
Seeing the glint of Confederate bayonets concealed in the Cornfield, Hooker halted his infantry and brought up four batteries of artillery, which fired shell and canister over the heads of the Federal infantry, covering the field. All at once, the cornfield exploded into chaos as a savage battle raged through the area. Men beat each other over the heads with rifle butts and stabbed each other with bayonets. Officers rode around on their horses sweating and cursing and yelling orders no one could hear in the noise. Rifles became hot and fouled from too much firing. The air was filled with a hail of bullets and shells. The Cornfield remained a bloody stalemate.
The Cornfield, an area about 250 yards (230 m) deep and 400 yards (400 m) wide, was a scene of indescribable destruction. It was estimated that the Cornfield changed hands no fewer than 15 times in the course of the morning.
When asked by a fellow officer where his division was, Hood (Confederate) replied, "Dead on the field."
The morning phase ended with casualties on both sides of almost 13,000, including two Union corps commanders.
Confederate men were in a strong defensive position, atop a gradual ridge, in a sunken road worn down by years of wagon traffic, which formed a natural trench.
A regimental chaplain, Father William Corby, rode back and forth across the front of the formation shouting words of conditional absolution prescribed by the Roman Catholic Church for those who were about to die.
Confederate Col. Gordon received four serious wounds in the fight. He lay unconscious, face down in his cap, and later told colleagues that he should have smothered in his own blood, except for the act of an unidentified Yankee, who had earlier shot a hole in his cap, which allowed the blood to drain.
The southernmost crossing of the Antietam. It would become known to history as Burnside's Bridge because of the notoriety of the coming battle. The road leading to it ran parallel to the creek and was exposed to enemy fire. The bridge was dominated by a 100-foot (30 m) high wooded bluff on the west bank, strewn with boulders from an old quarry, making infantry and sharpshooter fire from good covered positions a dangerous impediment to crossing.
The battle was over by 5:30 p.m. Losses for the day were heavy on both sides.
On the morning of September 18, Lee's army prepared to defend against a Federal assault that never came. After an improvised truce for both sides to recover and exchange their wounded, Lee's forces began withdrawing across the Potomac that evening to return to Virginia.
President Lincoln was disappointed in McClellan's (Union) performance. He believed that McClellan's cautious and poorly coordinated actions in the field had forced the battle to a draw rather than a crippling Confederate defeat.
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