McClellan planned to dismember Lee’s army piecemeal, first hitting hard on the Confederate left, then breaking Lee’s right to block his escape across the Potomac, then throwing four fresh divisions into the Rebel center for the coup de grace. It was a sound plan, but McClellan’s offensives were poorly coordinated. McClellan stayed well to the rear, keeping some 20,000 of his men in reserve. Had he pressed a lopsided advantage in numbers, he might have broken through and annihilated the Army of Northern Virginia; but he held back, convinced by faulty intelligence and vivid imagination that Lee’s forces outnumbered his own. At Antietam, McClellan, known for his caution and blustering talk, cemented his reputation for being the most tentative of generals.
Union Maj. Gen. Ambrose E. Burnside received orders to press Lee’s army below Sharpsburg, where a humpbacked bridge spanned Antietam Creek. Burnside held the advantage of 12,500 troops of his 9th Corps against some 4,000 Georgians from Maj. Gen. James Longstreet’s command. But the Confederate infantry, backed by two batteries of artillery in steep bluffs west of the creek, picked off hundreds of Union soldiers as they emerged from the trees and tried to cross the bridge, while others were shot or drowned fording the stream. It took Burnside’s troops three hours to cross the creek.
Many recruits, facing fire for the first time, turned and ran; two deserters from the newly formed 16th Connecticut Infantry kept going until they reached England, where they sat out the war. The urge to flee seemed perfectly human, even to Pvt. Thompson, the coffee-eating New Yorker, who kept moving forward as Minié balls buzzed by his head and comrades fell around him. “The truth is,” he wrote, “when the bullets are whacking against tree trunks and solid shots are cracking skulls like eggshells, the consuming passion in the breast of the average man is to get out of the way. Between the physical fear of going forward and the moral fear of turning back, there is a predicament of exceptional awkwardness from which a hidden hole in the ground would be a wonderfully welcome outlet.”
While the battle of the bridge slowly unfolded below Sharpsburg, an intense struggle broke out north of the town. At the center of Lee’s lines, some 10,000 Union troops tried to break through a Confederate front defended by 7,000 men.
The Rebels made their stand in an old farm lane known as the Sunken Road, eroded below the level of the surrounding fields by decades of wagon traffic. The trench gave the Confederates a protected position from which they unleashed fire on wave after wave of advancing Federals. The Yankees had to surmount the blind side of a knoll about 100 yards in front of the lane and cross exposed land above the Sunken Road, their heads silhouetted against the sky. They looked like figures in a shooting gallery. “Go away, you black devils! Go home!” the Rebels shouted, taking aim as each ragged line crested the hill. This part of the battle, which raged for three hours, was perhaps the most concentrated clash of the morning.
Within the tumult, a soldier from the 1st Delaware Infantry saw a comrade staggering around with both eyes shot out and pleading “for the love of God” for someone to end his agony. A lieutenant heard his appeal, verified its sincerity and coolly shot the blind man in the brain. “It was better thus,” the lieutenant said. Then a solid shot took the lieutenant’s head off, consigning another recruit to the army of the dead.
As the stricken cried out for mothers they would never see again, a woman in a bonnet secured by a red ribbon wandered among the fallen, binding their wounds and offering comfort as shot and shell gouged the earth around her. Clara Barton, a U.S. Patent Office clerk, was a self-appointed nurse who found her way to Antietam at the height of the fracas. As she kneeled to offer water to a wounded man, she felt a tug at her sleeve—it was a bullet, which ripped through her dress without touching her. It smacked into her patient, killing him outright. Unfazed, she straightened up, looked around for another soldier in trouble and went to work on him. The future founder of the American Red Cross never mended her torn blouse. “I wonder if a soldier ever does mend a bullet hole in his coat?” she said later.
After several hours, Union troops rushed forward to pour fire up and down the Sunken Road, knocking down hundreds of men. The dead and wounded tumbled together, lining the bottom of the declivity that would be known thereafter as Bloody Lane. The surviving Rebels scrambled out of the pit and Federals took possession, horrified by what they found. “In this road there lay so many dead rebels that they formed a line which one might have walked upon as far as I could see,” wrote Lt. Thomas L. Livermore of the 5th New Hampshire Infantry.
By 1 p.m., Lee’s center had broken. The survivors of Bloody Lane scuttled for the rear and formed a new defensive line on a ridge to the west. “We were already badly whipped and were only holding our ground by sheer force of desperation,” Longstreet recalled. Yet the thin gray line held. McClellan never tested it, husbanding his reserves for an imagined Rebel counteroffensive. “It would not be prudent to make the attack,” he said, overruling officers eager to swoop in for the kill.