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Pennsylvania was Robert E. Lee’s target in September 1862. But Maryland and George McClellan got in the way.

On September 13, 1862, Robert E. Lee’s Army of Northern Virginia was dangerously divided—stretched all the way from Boonsboro, Md., near the Pennsylvania border, to Harpers Ferry, Va., nearly 20 miles away across the Potomac River. Four days earlier, Lee had drafted Special Orders 191, his plan to secure his army’s supply line from the Shenandoah Valley while he crossed into Pennsylvania. Three columns under Thomas “Stonewall” Jackson, Lafayette McLaws and John Walker would capture Martinsburg, Va., and the Baltimore & Ohio Railroad, as well as the Union garrison at Harpers Ferry. Meanwhile, James Longstreet’s command would march to Boonsboro followed by the army’s supply wagons and General D.H. Hill’s division. Once Harpers Ferry was in Rebel possession, the army would reunite in Boonsboro or Hagerstown, Md.

Lee’s success depended on George McClellan’s well-earned reputation of hesitating before committing his Army of the Potomac to any action. But on the afternoon of the 13th, a copy of Lee’s plan, known to history as “Lee’s Lost Orders,” ended up in McClellan’s possession. Was it enough to enough to give McClellan the upper hand?

McClellan could hear cannon fire echoing off the mountains from the direction of Harpers Ferry, 20 miles west of his position at Frederick, Md., which convinced him the Confederates were attacking, just as prescribed in Lee’s orders—and that the Federals at the Ferry were still fighting.

Harpers Ferry was under the command of Colonel Dixon Stansbury Miles, a West Point graduate who had distinguished himself in the Mexican War. McClellan had placed Miles at Harpers Ferry in March; the town’s strategic location at the mouth of the Shenandoah Valley and along the route of the east-west Baltimore & Ohio Railroad made it a potential target from the outset of Lee’s Maryland invasion. On September 4, the first day of the invasion, Maj. Gen. John E. Wool had ordered Miles to “defend all places to the last extremity. There must be no abandoning of a post, and shoot the first man that thinks of it.”

“I am ready for them,” Miles responded.

But there was no attack. When Lee crossed the Potomac, he placed himself at Frederick, between Washington and Harpers Ferry, completely isolating Miles.

Then, on September 11, McClellan learned the Rebels had abandoned Frederick and were moving west toward Harpers Ferry and northwest toward Hagerstown. “Miles can do nothing where he is, but could be of great service if ordered to join me,” McClellan suggested to General in Chief Henry Halleck. Halleck refused. “There is no way for Colonel Miles to join you at present. His only chance is to defend his works until you can open communication with him.”

Halleck was not being intransigent, but practical. Where could Miles go? He already was surrounded at a distance. He couldn’t move west— Stonewall Jackson was there, having just seized Martinsburg. He couldn’t go north—Lee would nab him at Hagerstown. He couldn’t go east—Confederates held those routes, too. The only path apparently open was from the south—the wrong direction for an attempted Union escape.

On a ridge west of Harpers Ferry, Stonewall Jackson was frustrated. First, he was behind schedule. Special Orders 191 called for the operation to begin September 12. It was now September 13, and Jackson’s Confederates were just arriving on the mountains surrounding the town. Otherwise, all was according to plan, though Jackson faced a communications problem. Three mountains and two rivers separated his command, with a Union garrison positioned in between. He attempted to remedy this problem through signal flags, but when that failed, he dispatched couriers in all directions.

Complicating matters, the weapons carried by Jackson’s infantry did not have the range to do any harm from their positions on Maryland and Loudoun heights. The bullets from their muskets couldn’t reach the Yankees below. Nor could Jackson easily deploy his men from either height to invest the town. Miles remained safe on Bolivar Heights, protected by the natural moats of the Potomac and Shenandoah rivers and the rugged terrain of the area.

Jackson knew he had to force the issue. An artillery barrage would compel Miles to submit.

By the afternoon of September 13, Miles knew he and his garrison were in peril. Confederates were everywhere. Loudoun Heights, overlooking the Shenandoah River, was the first to fall. Jackson then seized School House Ridge, where he began menacing Miles’ lines on Bolivar Heights.

Atop Maryland Heights—the tallest mountain hovering over the Ferry, and the key to the position—Miles fought his battle. His men must hold Maryland Heights. But after nine hours, the bluecoats were abandoning the heights. “God Almighty!” screamed the astonished colonel from his command post on Bolivar Heights, more than two miles away. “What does that mean? They are coming down! Hell and damnation!”

Miles was now surrounded, but not yet surrendered. In desperation, he attempted that night to inform Union authorities of his predicament. He instructed a Maryland cavalry officer familiar with the locale to pass through enemy lines and “try to reach somebody that had ever heard of the United States Army, or any general of the United States Army, or anybody that knew anything about the United States Army, and report the condition of Harpers Ferry.” Miles told the messenger to inform McClellan that “he could hold out for 48 hours.”

McClellan, meanwhile, was planning Miles’ rescue. His nearest force was about 15 miles from Harpers Ferry. From Special Orders 191, McClellan knew six of nine infantry divisions in Lee’s army were there. Two of them were assigned to take Maryland Heights. If McClellan could recapture Maryland Heights—or engage that force long enough to permit Miles’ escape—he would spoil Lee’s operation.

McClellan prepared specific instructions for VI Corps commander Maj. Gen. William B. Franklin. “I have now full information as to movements and intentions of the enemy. The firing [at the Ferry] shows that Miles still holds out. You will move at daybreak….I have reliable information that the [South Mountain] pass is practicable for artillery and wagons. If this pass is not occupied by the enemy in force, seize it as soon as practicable…in order to cut off the retreat of or destroy McLaws’ command…. Having gained the pass, your duty will be first to cut off, destroy, or capture McLaws’ command and relieve Colonel Miles.”

McClellan issued the order at 6:20 p.m. It was almost dark, and the cannons booming at Harpers Ferry had ceased. An hour before midnight, he reported to Halleck: “An order from General R.E. Lee which has accidentally come into my hands this evening—the authenticity of which is unquestionable—discloses some of the plans of the enemy, and shows most conclusively that the main Rebel army is now before us. This army marches forward early tomorrow morning, and will make forced marches, to endeavor to relieve Colonel Miles. I shall do everything in my power to save Miles if he still holds out.”

Halleck expressed no enthusiasm for McClellan’s discovery, still concerned that the entire Rebel movement was a ruse to draw troops away from the protection of Washington. He especially worried that in his ardor to move on Harpers Ferry, McClellan had pulled away all Union troops guarding the Potomac. The river crossings were now vulnerable. “Scouts report a large [Confederate] force still on Virginia side of the Potomac, near Leesburg,” Halleck informed McClellan. “If so, I fear you are exposing your left flank, and that the enemy can cross in your rear.”

McClellan, now more than 50 miles from Washington, remained focused on the Rebels in front of him rather than a potential enemy behind him. Shortly after his cavalry confirmed the Confederate positions outlined in Special Orders 191, he devised a two-pronged offensive. Franklin would move to relieve Harpers Ferry. General Ambrose Burnside would drive against the Rebels at Boonsboro, defeat them and beat them to the Potomac, cutting off their avenue of escape.

Boonsboro was a small farming village of about 1,000 inhabitants along the National Road beneath the western shadow of South Mountain. Lee had identified Boonsboro in Special Orders 191 as the original objective of Longstreet’s command, as it was only 12 miles north of Harpers Ferry—a good rendezvous point for Jackson after he defeated the Ferry’s garrison. Lee, however, had shifted Longstreet to Hagerstown on September 11, leaving only the rear guard of the army at Boonsboro.

If McClellan could sweep away this rear guard with Burnside’s thrust and then rush to the Potomac at Williamsport, he could sever Lee’s line of retreat and trap him in Maryland. McClellan usually believed the Confederates outnumbered him; in this case, with Lee’s army divided and scattered and its wings separated by more than 20 miles, McClellan sensed a numerical advantage. Never had he felt so confident.

General Lee was anything but confident on September 13. Jackson was late in getting to Harpers Ferry. Reports arriving in Hagerstown from his cavalry scouts showed McClellan being uncharacteristically aggressive, moving Federals west from Frederick toward South Mountain. Lee recognized his vulnerability. If the enemy crossed that mountain, his position in Hagerstown became untenable. Even worse, McLaws’ command north of Harpers Ferry would be trapped.

What was happening?

Lee turned his attention away from Pennsylvania, at least for the moment. Late on the 13th, he decided to move Longstreet’s command from Hagerstown and march it south toward Boonsboro to support Maj. Gen. D.H. Hill’s rear guard near South Mountain. He also sent a courier to McLaws with the disturbing message that “the enemy is moving toward Harper’s Ferry to relieve the force they have there. You will see, therefore, the necessity of expediting your operations as much as possible.”

The next morning, Lee learned masses of Federals approached South Mountain. He moved Longstreet even closer; it appeared the Yankees intended to flood over the mountain.

South Mountain is a north-south ridge that starts at the Potomac River and runs 37 miles across Maryland before crossing into Pennsylvania and continuing north to Carlisle. If the Federals penetrated any of the Rebels’ five southern-most gaps—spread over 14 miles—it would mean disaster. None of them could be lost.

Lee never anticipated this problem. The unexpected resistance Jackson met at Harpers Ferry had stalled his army. Now the invasion of Pennsylvania was deferred. Lee needed Harpers Ferry to collapse. If, indeed, the Federals were determined to advance against South Mountain, Lee must stop them. He had no other choice.

Sunday, September 14, arrived with Jackson’s Confederates laboring feverishly to haul cannons up the rugged and precipitous slopes of Maryland and Loudoun heights. Miles did not anticipate this; in fact, he considered the feat impossible. But Jackson excelled at turning impossible into possible; by early afternoon, long-range rifled cannons were in position.

“Should we have to attack, let the work be done thoroughly; fire on the houses where necessary,” Jackson ordered McLaws. “The citizens can keep out of harm’s way from your artillery. Demolish the place if it is occupied by the enemy, and does not surrender.” Confederate cannoneers began yanking their lanyards as 1 p.m. approached, and for the next five hours, iron shells hailed upon the Federal garrison trapped below the mountains.

“I saw two, three, four, half a dozen puffs of smoke burst out,” recalled Captain Edward Hastings Ripley of the 9th Vermont Infantry, posted on Bolivar Heights. Suddenly, in the very center of the Union lines, “there was a crash, then another and another, and columns of dirt and smoke leaped into the air, as though a dozen young volcanoes had burst forth.”

“At first, their missiles of death fell far short of our camp,” recalled Lieutenant James H. Clark of the 115th New York Infantry, “but each succeeding shell came nearer and nearer, until the earth was plowed up at our feet, and our tents torn to tatters.”

Even Miles’ aide-de-camp, Lieutenant Henry Binney, was rattled by the intensity of the iron storm cascading from the mountains. “The cannonade is now terrific. The enemy’s shell and shot fall in every direction; houses are demolished and detonation among the hills terrible.”

Local resident Mary Clemmer Ames scampered to her cellar and entrenched herself in an empty piano box “to escape the earthquake from above…. The windows rattled; the house shook to its foundations,” she wrote. “Heaven and earth seemed collapsing.”

Nightfall brought an end to the merciless pounding, but no white flags. The Yankees remained obstinate.

Meanwhile, Jackson received word that McLaws, on Maryland Heights, was in danger from approaching Federals. Jackson had to do something fast. Thus far, he had been reluctant to utilize his infantry. The only place he could advance his foot soldiers was across a low valley between School House Ridge and Miles’ position atop Bolivar Heights. Miles held the height advantage, buffered by a near perpendicular slope of almost 300 feet. The space across the valley was open pasture, making Jackson’s men easy targets for Union gunners. A frontal assault might not work—might even prove fatal.

Jackson recalled from his days in command at Harpers Ferry 17 months earlier that a level plateau called the Chambers Farm, overlooking the rapids of the Shenandoah, constituted the extreme southern edge of Bolivar Heights. If he could move men and cannons there, he would be behind Miles. Jackson summoned his most experienced division commander, Maj. Gen. A.P. Hill, and ordered him to skirt the Shenandoah in the darkness and to seize Miles’ left flank.

In an amazing conquest of terrain, Hill moved 5,000 men and 20 cannons during the night, quietly posting them behind the Union line. There he waited for the sun to rise.

Jackson felt confident that the morrow would bring him victory.

Miles knew the noose was tightening. He had heard nothing from his attempt to communicate with the Army of the Potomac the day before. Where was McClellan?

The Union commander was on the march toward South Mountain with four corps—13 divisions total. “The morning church bells rang out clearly,” observed a cheerful John M. Gould of the 10th Maine Infantry as his regiment marched through Frederick that Sunday. “It was the most pleasant sound I have heard for a long time. After all, civilization is a fine thing.”

Gould was marching near the rear of the army when his unit arrived at the top of Braddock Gap in the Catoctin Mountains. Before him was the panorama of the Middletown Valley, bordered on its western edge by South Mountain. Gould could see powder smoke rising from the mountain. He heard the thumping discharges of artillery. Battle was under way.

For the first time since September 1, McClellan’s army was engaged. Burnside’s men clawed their way up South Mountain’s eastern slopes, but Lee’s Confederates refused to yield. For 12 hours—from 9 a.m. until almost three hours after dusk—Jesse Reno’s IX Corps attempted to breach and hold Fox’s Gap. They failed. One mile north at Turner’s Gap, Lee’s men made a resolute stand against a U.S. brigade, maintaining control of the gap and the critical artery of the National Road. Success for the Yankees finally came one mile farther north at Frostown Gap, where Joseph Hooker’s I Corps overwhelmed a greatly outnumbered Alabama brigade. But darkness stalled the momentum. When the firing finally ceased, men from opposing sides were so close they could converse without raising their voices.

Lee still held the crest of South Mountain.

Farther south at Crampton’s Gap, Franklin’s rescue mission to Harpers Ferry had begun. McLaws, also focused on Harpers Ferry, had not prepared—his rear guard was dangerously outmanned and outgunned, while McLaws himself was on Maryland Heights watching as Confederate troops bombarded the town. But Franklin didn’t know McLaws’ disposition, and he approached Crampton’s Gap with deliberation and caution. Three hours passed as his civil engineer’s mind calculated the advantages and disadvantages of striking. Once he moved, the battle ended quickly. There were too many Yankees for the Confederates to withstand. They fled up the mountain’s east slope with the Federals in hot pursuit. McLaws and Jeb Stuart arrived to mend the hole, but were too late. Franklin owned the gap—and 400 prisoners from 17 different Rebel units. Darkness settled over Pleasant Valley, preventing further Confederate catastrophe.

Lee’s first retreat as commander of the Army of Northern Virginia occurred as he abandoned Fox’s and Turner’s gaps at South Mountain late September 14. He had achieved one goal: The enemy did not break through his mountain fortress. But a defensive battle at South Mountain never was part of Lee’s invasion strategy.

Lee saw his invasion crumbling. The most important matter now was not Pennsylvania, but preservation of the army. “This army will go by Sharpsburg and cross the river,” he said in a dispatch to McLaws.

Sharpsburg, Md., was Lee’s quickest escape route. Two good roads led from the Boonsboro area to the village, which straddled Antietam Creek. A night retreat would protect the army from Union detection. The march to the Potomac would be about 10 miles, not overly taxing, but difficult in the darkness. Lee knew his men were fatigued. Some had been awake for 24 hours with little or no food. If he could return the army to Virginia, he presumed it would be safe. Surely McClellan would not follow him into the Confederacy.

Retreat also held an advantage in reuniting the army. Momentum would be lost, but the army would be saved. Plenty of fight and enthusiasm remained for a future invasion. Once reunited in Virginia, Lee’s Rebels could race to Williamsport and launch into Maryland again—assuming McClellan had not seized the Williamsport crossing first. Or, Lee could simply terminate the campaign, rest and reorganize his army, and consider another venture into Yankee country at a more opportune time.

But this was the opportune time. The week before, the Confederacy was charged with confidence. Bold proclamations to end the war were issued. The Confederate Congress and the Rebel press demanded invasion. Southern peace terms were publicly presented. What would retreat mean for the South’s rising surf? And how would it affect Northern campaigns for the upcoming midterm election? Surely Lincoln’s Republicans would trumpet Lee’s withdrawal as proof that competent Republicans were managing the war and should be returned to office.

On the diplomatic front, Europe had been impressed with the recent flurry of Confederate triumphs. Would a retreat defeat recognition of Southern independence, especially after the bravado of invasion had stirred editors of British and French newspapers?

During the somber and sullen night march, Lee changed his mind. He needed a path of escape for Lafayette McLaws and his 8,000 troops now trapped in Pleasant Valley. McLaws’ only route to safety was due west, on mountain roads that led to Sharpsburg. Lee would cancel the action at Harpers Ferry. His army would stop near Sharpsburg to wait for McLaws, and then return to Virginia. “It is necessary for you to abandon your position tonight,” Lee told McLaws. “Your troops you must have well in hand to unite with this command.”

What Lee didn’t know was that he was canceling the Harpers Ferry operation just as Jackson was assured of victory. “Through God’s blessing, the advance, which commenced this evening, has been successful thus far, and I look to Him for complete success tomorrow,” he reported to Lee.

God had not, however, shown blessing to the Confederates on this Sunday. Lee prepared to reunite his bruised army for another battle on another day. He headed for Sharpsburg, settling in on the west side of meandering Antietam Creek.


Adapted from September Suspense by Dennis E. Frye, Antietam Rest Publishing, 2012.

Originally published in the September 2012 issue of America’s Civil War. To subscribe, click here.