While many consider the Battle of Gettysburg (July 1 – 3, 1863) to be the turning point of the American Civil War, in truth the outcome of the war was decided the year before with the Battle of Antietam (also known by it's Southern name, the Battle of Sharpsburg).
After the Battle of Second Manassas (also known as Second Bull Run, which was fought from August 28 – 30, 1862), and the Union's rearguard action at Chantilly, Confederate General Robert E. Lee conceived of a bold plan to invade the North. So far in the Eastern Theatre Virginia had taken the brunt of the war. The area around Manassas was stripped bare. Retreating to Richmond would give up the advantage Lee had achieved by decisively defeating the Union Army of Virginia. His army lacked the munitions to lay siege to Washington. He needed food and supplies for his army. Retreating to the Shenandoah valley would give him that, but it would leave most of northern Virginia open once more to Union forces while giving up the initiative. There was some pro-Southern sentiment in Maryland, which he hoped to encourage, possibly to the point of having Maryland leave the Union. His invasion plan would also bring the war to the people of the North, which might prompt the Union to end the war. There, too, was the ever present thinking that if the Confederates could show that a Southern victory was inevitable official recognition by Britain and France wouldn't be far behind. Britain and France were close to interceding on the Confederacy's behalf and another Confederate victory could prompt them into action.
Lee's plan was to slip away from the Union army and drive up the Shenandoah Valley into Maryland. From there, he could proceed north into Pennsylvania. Though he kept this from Jefferson Davis, the president of the Confederacy, Harrisburg — Pennsylvania's capital — was his intended target. By destroying the large railroad bridge across the Susquehanna River, Lee could severely hamper the Union's supply route from the north. Also on Lee's list of possible targets were Philadelphia, Baltimore and Washington itself, left open if Lee could strike a well aimed blow at the Army of the Potomac.
While Lee was preparing for his invasion, the Union Army of the Potomac was undergoing another period of reconstruction. Lincoln, unhappy with Major General John Pope's handling of the Second Manassas campaign, relieved him of command of the Army of Virginia. Maj. Gen. George McClellan was put in command, once again, of all the Union forces around Washington (though not without reservations). He rolled the Union's Army of Virginia into his own Army of the Potomac, reorganizing the army and boosting the morale of the soldiers, if not Washington's politicians. Not only was McClellan not a unanimous choice, but he had come close to being sacked himself.
McClellan graduated from West Point second in his class in 1846. He was trained as an engineer and entered the army during the Mexican War. Due to slow promotions in the regular army, he transferred to the cavalry in 1855. As a captain, he spent a year in Europe, where he reported on the siege of Sevastopol during the Crimean War. He developed a modified saddle — the McClellan saddle — that was used not only in use with the American army, but also used by the Prussian and Hungarian armies (the saddled remained in use with those armies until they phased out horse cavalry in the 20th Century). He left the army in 1857 to become chief engineer and vice president of the Illinois Central railroad. He became a division president of the Ohio & Mississippi Railroad just before the war. As a railroad man McClellan met and befriended Ambrose Burnside, who would soon become one of McClellan's subordinate generals.
McClellan rejoined the army in 1861, where a series of successful campaigns in West Virginia and Kentucky brought him notice in Washington. He lobbied for the retirement of Winfield Scott, the aged general in charge of the army who first promoted him in the Mexican War; McClellan hoped to take his place. McClellan's engineering and organizational abilities came to the fore when he built the Army of the Potomac after the Bull Run disaster. His success at this should not be understated. He took a green, demoralized army and built it into a potent fighting machine. Whatever his other failings, his skills as an organizer were readily apparent. "The Little Napoleon" was put in charge of all Union armies — replacing Winfield Scott, as he had hoped — in spite of his tendency to ignore the civilian politicians who were ultimately his superiors.
He was urged to march on the Confederates throughout the remainder of 1861 and early 1862 but nothing would move him. The Confederate army still sat at Manassas, Virginia, where they had won their first major victory. Lincoln's administration pushed McClellan to strike at the Rebels, but McClellan would not be moved until he was good and ready. He continuously over estimated the size of the Confederate force. He employed Allan Pinkerton, the famous detective, to furnish him with military intelligence. Pinkerton's estimates of Confederate troop strength were severely inflated, but the cautious McClellan took them at face value. McClellan felt that he didn't have enough men to assault the 115,000 Confederates he was sure defended Manassas. In December 1861 he was laid low by typhoid. In February he accompanied 40,000 troops to secure the Baltimore and Ohio Railroad at Harper's Ferry, as part of a plan to secure Washington. A permanent pontoon bridge needed to be rebuilt there with parts sent up via the Chesapeake and Ohio Canal. When he got there, McClellan found the pontoons were 6 inches too wide to fit in the lift locks along the canal. He and most of his troops tromped back to Washington. A week or so later, in early March, it was determined that the Confederates had retreated from Manassas. In the defensive positions were found "Quaker guns", logs painted black to make them look like cannons from a distance. The size of the Rebel army had been severely over estimated.
McClellan set about devising a new plan to march on Richmond via the peninsula between the James and York rivers. It was a good plan but McClellan was too cautious. He moved out in March, 1862 as the commanding general of the Army of the Potomac, relieved of his duties as commander-in-chief (this position went unfilled until Henry Halleck was given the position on July 11, 1862). When his army came up to the Rebel defenses at Yorktown on April 3, McClellan estimated that he had about 58,000 men versus 15,000 entrenched Rebels. He decided to lay siege to the town and began bringing up his siege guns. On April 7 he estimated the Rebel army before him at about 100,000 men, if not more. He continued to call for more men, claiming his army was woefully outnumbered. McClellan wasted a month bringing up siege guns and begging for more men. The day before the siege of Yorktown was to begin, they found the Rebel lines were deserted. The small Confederate force had left the night before, having delayed the Army of the Potomac for more than 4 weeks. Although outnumbered, the Confederates managed to retreat to Richmond virtually unscathed.
Joseph Johnston attacked McClellan at Fair Oaks on May 31 and June 1. McClellan repulsed the Confederates with great difficulty. Robert E. Lee took command after Johnston was wounded in the battle. Pinkerton estimated Lee's army at about 200,000 men, more than twice as many as Lee's actual total of 85,000. It was Lee who was outnumbered against the Army of the Potomac's 105,000, but Lee took the initiative and struck McClellan on June 25. Although the resulting series of battles known as the Battles of the Seven Days were mostly Union victories, McClellan failed to follow up; instead he retreated, blaming everyone but himself. He continued playing politics, blaming his defeat on being vastly outnumbered while denied reinforcements by the scoundrel politicians in Washington. He boxed himself in at Harrison's Landing, effectively removing the Army of the Potomac as a threat to Robert E. Lee.
Maj. Gen. John Pope, newly arrived from the west, was given command of the disparate Union forces in northern Virginia with the hope that Pope would do what McClellan could not: defeat Lee's army. This newly formed Army of Virginia moved on Lee while McClellan was ordered to pull out of the Peninsula and support Pope's army. McClellan resented Pope and the Lincoln administration. The corps of Maj. Gen. Fitz John Porter, Maj. Gen. Samuel Heintzelman and Brigadier General Jesse Reno of McClellan's army were moved to support Pope during the Second Manassas campaign. On August 27 McClellan was slow to move up Brig. Gen. Edwin Sumner's Second Corps and Brig. Gen. William Franklin's Sixth Corps, claiming they were not ready to advance to Pope's aid. On August 29 McClellan used the spectre of a mythical army of 120,000 men falling on Washington when he said to Lincoln in a telegram, "I am clear that one of two courses should be adopted: 1st, to concentrate all our available forces to open communications with Pope; 2nd, to leave Pope to get out of his scrape, and at once use all our means to make the capital perfectly safe." While McClellan might not have been out-and-out sabotaging Pope, he certainly wasn't making Pope's job any easier. As McClellan defended Washington with his stripped down Army of the Potomac, Pope's Army of Virginia was soundly defeated by Lee at the Second Battle of Bull Run (Manassas).
After the Second Manassas debacle Lincoln had little choice but to place "Little Mac" back in command of the eastern armies. This was a hard decision for Lincoln to make, as he had little confidence in "the Young Napoleon". In fact, Secretary of War Edwin Stanton was petitioning to have McClellan removed, citing McClellan's conduct during Second Manassas as just one of the reasons. Lincoln, though, had few options. He approached Maj. Gen. Ambrose Burnside about taking over the army. Burnside was one of the few corps commanders with experience in independent command, after a very successful operation the previous year in North Carolina. Burnside was a likable man with few political aspirations, but one who knew his limitations. He turned down Lincoln as he felt he wasn't able to command the entire army. Another likely candidate was Fitz John Porter, but he was embroiled in controversy over his conduct during Second Manassas, and he was just as political as McClellan. The only other immediate candidate was Maj. Gen. Joseph "Fighting Joe" Hooker. Hooker was known for his conducting his own intrigues, and had a disreputable reputation. Lincoln wasn't ready to give the command to Hooker, and Lee's troop movements at the beginning of September meant that Lincoln had run out of time. Lincoln gave McClellan the Army of Virginia, to be folded into his own Army of the Potomac. Once again, McClellan was the primary Union battlefield commander in the eastern theatre.
The South's best chance of victory in the war was recognition by Britain and France. If those two nations chose to put pressure on the North to come up with a peace treaty, the Union would have little choice but to negotiate. France was considered to have the world's best army, and Britain had without a doubt the finest navy. Between them they had the military power to force a settlement on the North. The two countries already favoured the South, with British newspapers decrying the "barbarous" conduct of Union armies on Southern soil. Britain's textile industry relied on Southern cotton. The only reason why the Union embargoes hadn't crippled that industry was due to two years of cotton surpluses before the war resulting in a glut of cotton in British warehouses. The South had deliberately held back cotton exports (part of its "King Cotton" strategy) in 1861 but saw that Britain could not be coerced that way into recognizing the South. Cotton now moved through the Union blockades, but not in enough quantity to relieve the pressure on British textile workers. Even with this pressure, neither Britain nor France was willing to "back a loser". The Confederacy had to be seen as the inevitable winner of the struggle before the European powers would intervene. This meant taking the war to the North. Braxton Bragg and Kirby Smith had already set out from Tennessee into Kentucky. They planned to link up and recapture Kentucky, perhaps even moving into the Ohio valley. If Lee, or Smith and Bragg could win a major victory on Northern soil, or capture a major Northern city, European recognition was likely.
Lincoln, too, needed a victory. For some months Lincoln had thought about the form a reunited nation would take. Some Democrats, like McClellan, wished for a return to status quo. The more radical elements in the Republican party wanted major changes in the event that the Union was preserved. In particular, they wanted the elimination of slavery. Abolitionists were a minority in the North, but a vocal minority that was gaining influence. Up until that point, the war had been fought by the North to preserve the Union. The South, by contrast, held the Union as invaders intent on forcing them back into the Union. The South had the moral high ground. Lincoln intended to take away that moral high ground by broadening the war. He wanted emancipation of the slaves to be an end result of a Union victory.
This position was a political minefield for Lincoln. There were many in the army who would throw down their arms if they thought they were fighting to free the slaves. The border states of Kentucky, Maryland, and Missouri might secede and join the Confederacy over the issue. There was also the constitutionality of the administration unilaterally freeing the slaves. The document that Lincoln prepared is one of the most amazing documents produced in the English language. His Emancipation Proclamation would free the slaves only in territory captured by the Union after the enacting of the Proclamation, set for January 1, 1863. Slaves in territory already held by the Union, such as parts of captured Tennessee or the slave state of Delaware, would not be freed, at least not without compensating their masters. What this said to the South was that there would be no status quo. Either the Southern states would rejoin the Union by the end of 1862, or they would lose the institution of slavery with no compensation.
With this Proclamation, Lincoln had taken the moral high ground. The European powers, which were already against slavery, would be clearly supporting a slave state if they recognized the Confederacy. Lincoln had changed the tone of the war by introducing an end to slavery as a moral component to the North's "invasion" of the South.
Lincoln showed his Emancipation Proclamation to his cabinet in July of 1862. They were generally in favour of it. Some of his cabinet members were surprised that he had gone as far as he did, as Lincoln had always previously stated that slavery was not the core issue of the war. However, there were concerns. There was the possibility of mutiny within the Union armies. There was also the possibility of riots in Northern cities from Northerners who had no intention of fighting a war to free the slaves. Finally, releasing the Proclamation at that time, with the Union army in the east reeling, would look like the last act of a desperate nation. It could inadvertently result in Britain and France recognizing the South. Lincoln agreed to hold off releasing the Proclamation until after a major Union victory.
The next major victory could very well decide the war.
On September 4, 1862, Lee moved his troops across the Potomac River. By the 7th, they had arrived south of Fredrick, Maryland. This movement was anything but straightforward. The Army of Northern Virginia's supply line was long and tenuous. The troops had to forage for food. Maryland, being a border state, was politically sensitive. Lee had given strict orders that food and essential supplies would be paid for, even if that was in Confederate scrip, considered worthless by many in the North. The locals, for their part, mostly feared the Southern army. Rumours that they would lay waste to Maryland circulated. This portion of Maryland had fairly strong Union leanings, and many saw Lee's army as an invasion, not a liberation. Lee had hoped for secessionists to rise up along with the army and join its ranks, but probably no more than 200 did.
Straggling was a major problem for the Army of Northern Virginia. Many of the soldiers had no shoes, making the march slow and painful for them. Though they tried to keep up with their comrades, they couldn't help but fall behind. They were joined by soldiers less prone to face death again, who found it relatively easy to mix with the other stragglers. Sickness, mostly from a poor diet high on raw corn, reduced they army's numbers even more.
McClellan was slow to react to Lee's movements. Little Mac had little idea of Lee's intended destination. Instead, he chose to cautiously shadow the Rebel army. To be fair, McClellan was reorganizing his army on the fly. Reporting directly to him were three subcommanders, each in command of a wing. The left wing of the army was under Maj. Gen. William Franklin, and consisted of his own Sixth Corps plus a division under Maj. Gen. Darius Couch. Franklin was considered to be slow and lacking in energy by McClellan. The centre was commanded by Maj. Gen. Edwin Sumner, and consisted of Sumner's Second Corps and Brig. Gen. Alpheus Williams' Twelfth Corps. Sumner was the oldest of the army corps' commanders. Forty years of service had stripped any imagination out of the old warrior. The Twelfth Corps was new to the Army of the Potomac, having fought in Pope's Army of Virginia under Nathaniel P. Banks. Williams was a temporary commander, though, as it was soon to be taken over by an older regular army officer, Maj. Gen. Joseph K. F. Mansfield. The right wing was under McClellan's friend Ambrose Burnside, and contained Burnside's own Ninth Corps (now under General Jesse L. Reno) and the First Corps under Maj. Gen. Joe Hooker. Hooker's corps was another transplant from the Army of Virginia. As it became clear that Lee intended to invade Pennsylvania, that state's governor, Andrew G. Curtin — an important Republican — requested one of its native sons to command the state's militia. That man was one of First Corps' brightest division commanders, Brig. Gen. John F. Reynolds.
Another of McClellan's reorganizations had to do with the Federal cavalry. The cavalry arm was ineptly used by Pope. McClellan reorganized it as five brigades under a single commander, Brig. Gen. Alfred Pleasanton. Though much more effective, the Federal cavalry was unable to penetrate the screen set up by Confederate Maj. Gen. J.E.B. ("Jeb") Stuart's cavalry, thus McClellan had no accurate count on the enemy's size.
On September 9, Lee drafted his Special Order 191 outlining a plan to split his army in four parts. He had expected the Federal garrisons at Martinsburg and Harper's Ferry to simply evacuate, that being the prudent course of action. When Lee learned that the garrison still held Harper's Ferry, he ordered Maj. Gen. Thomas "Stonewall" Jackson's corps and parts of Maj. Gen. James Longstreet's corps to approach Harper's Ferry from three points and attack it. The fourth portion of the army, under Longstreet, would continue to advance up the valley. Harper's Ferry in particular was a prize worth taking, due to its store of supplies, let alone the fact that Lee could not leave its 7,500 troops behind in his rear. Harper's Ferry would be taken in 3 days and the army would combine again at Boonsboro. The plan called for Jackson to take the town by the 12th of September.
Jackson's forces, however, didn't converge on Harper's Ferry until the 13th. Two divisions under Maj. Gen. Lafayette McLaws (consisting of his own division and that of Brig. Gen. Richard Anderson) struck Maryland Heights, a strategically important mount overlooking all of Harper's Ferry. Brig. Gen. John Walker's division of two brigades attempted to destroy the railroad bridge at Monocacy (they were not successful) and then went on to capture Loudon Heights, overlooking Harper's Ferry from the east. The longest route was taken by "Stonewall" Jackson's corps. They had hoped to cross the Potomac by travelling through the village of Sharpsburg and crossing at nearby Shepherdstown, but he discovered that the Martinsburg garrison had not retreated. This precipitated a change in his route, adding 60 miles to the distance travelled by his corps. As he moved on Martinsburg, the garrison fled to Harper's Ferry. Instead of taking Harper's Ferry on September 12, Jackson was leaving Martinsburg on that day. The attack on the Yankee garrison at Harper's Ferry didn't begin until the 13th.
Meanwhile, incorrect reports of Pennsylvania militia moving south from Hagerstown caused Lee to split off some of Longstreet's lead elements to deal with this supposed threat. This left a small force to guard the passes over the mountains that shielded Lee's army from McClellan's. Splitting an army in the face of the enemy was a risky move at the best of times, but now Lee had split his army into 5 pieces. It was a calculated risk that Lee thought worth taking, for he knew McClellan's character and did not think McClellan capable of making a bold move in the face of uncertainty.
The reason Harper's Ferry and the Martinsburg garrison had not been relieved was due to bureaucratic infighting in the Union command structure. Both defensive garrisons fell under the command of Maj. Gen. John E. Wool, at the area departmental headquarters in Baltimore. He wasn't privy to McClellan's intelligence gathering and was physically distant from the garrisons so as to be unable to command them effectively. McClellan wanted those garrisons, and their troops, for his own army but he didn't have the authority. Halleck, not being one to take risks that could cause harm to his career, sidestepped the issue. He required that Harper's Ferry hold on against a Confederate onslaught, but left Wool in command of the garrison.
Lee's movements, and Pleasanton's inability to break through Stuart's screens, left McClellan with an unclear picture of Lee's intentions and the size of Lee's force. Reports came in of Confederates marching on Hagerstown, of Jackson doubling back to re-cross the Potomac in an effort to get around McClellan and strike Washington, of troops on the Harper's Ferry road, and of Confederates already across the Potomac. This latter report frightened Halleck, who insisted that — first and foremost — McClellan defend Washington. Reports from citizens (many of whom had never seen as many men in one place as Lee's army columns) gave exaggerated accounts of the number of Rebels. Captured stragglers made a game out of overstating the size of the Rebel army. Pleasanton took as gospel the report of a notoriously unreliable scout that Jackson's force numbered 100,000 men. In the absence of reliable information, and with the weight of saving the Union on his shoulders, McClellan reverted to his penchant for inflating the size of his enemy's forces. Erroneous reports put a total of 200,000 men at Lee's disposal in Virginia. On September 8 McClellan believed that most of the Confederate army had not yet crossed the river, though 75,000 Rebels occupied the area around Frederick. In fact, Lee's army numbered less than 50,000 by this point, while McClellan had 85,000 men in the field and another 72,500 — including a corps under his trusted friend Fitz John Porter — manning the defenses at Washington. By September 9, McClellan had managed to inflate — in his mind — the size of the Army of Virginia to about 3 times its actual number.
With such a large army in front of him and Halleck's order to protect Washington, McClellan moved cautiously, even halting for an attack when he heard a report there were troops heading straight for him. The army moved at the leisurely pace of about 10 miles a day. March discipline was lacking in the Army of the Potomac, with a lot of straggling and unauthorized foraging (the residents of Maryland soon thought the Confederates were better "guests"). McClellan informed Halleck that he would move immediately and quickly as soon as he definitely knew Lee's intentions.
On September 13, in a meadow near Fredrick, camped the 27th Indiana regiment of the First Division, Twelfth Corps. A Rebel division may have been camped in the meadow a few days before, though there is no definitive proof of this. The 27th Indiana found a section of meadow near a rail fence and rested there. Two Union soldiers — Corporal Barton W. Mitchell and Private John Campbell — were chatting when Mitchell noticed a bulky envelope in a patch of tall grass and picked it up. Inside the envelope were three cigars wrapped in a piece of paper with writing on both sides. Looking at the paper, with Campbell reading over his shoulder, he found that it was a copy of Lee's Special Order 191. The two took the package Sergeant John M. Bloss, who took Mitchell to Captain Kopp, their company commander. Kopp sent them on to Colonel Silas Colgrove, their regimental commander. Colgrove sent Mitchell and Bloss back to their regiment (without so much as the cigars as a reward) and then he went straight to his Corps commander, Brig. Gen. Alpheus Williams. What happened to the cigars is unknown.
There was every reason to believe the order was genuine. The order was signed by Col. R. H. Chilton, Lee's adjutant. According to Colgrove after the war, Col. Samuel E. Pittman of Williams' staff knew Chilton before the war and recognized his signature. This couldn't have been the case, as Pittman entered the army 5 months after Chilton resigned. Even still, the order seemed genuine. It would have been very unlikely for the orders to have been a trick. Placing such a ruse in a meadow, hoping the Yankees would stumble across it, was very unlikely. Williams sent it on to McClellan.
McClellan was in his tent discussing the army's occupation of Frederick with some local citizens when the order arrived. When he saw it, the cautious McClellan said, "Now I know what to do!" Even so, he was slow to react. He sent a gloating telegram to Lincoln, but then started to have second thoughts. McClellan feared that the order's timetable had been disrupted. He had reports of troops near Williamsport and of a Rebel force at Hagerstown, neither of which were in the orders. Fearing that the order's timetable had been disrupted or thrown away entirely, he asked Pleasanton to check if the routes of march had actually been followed. Pleasanton reported that he thought the routes had been followed, thus the orders were valid. In fact, Lee's timetable had slipped but Pleasanton's cavalry spotted the one Confederate regiment where another should have been, misidentified it, and assumed the timetable was still valid. Yet another stroke of luck fell McClellan's way.
Another aspect of the Orders was that McClellan now had a reasonably accurate estimate of the size of Lee's army. Only McClellan chose not to believe these numbers. Allan Pinkerton, the famous detective, and Pleasanton had given McClellan intelligence information that was quite wrong. McClellan felt he was opposing a force of 120,000 men out of an estimated 200,000 available to Lee, but the arithmetic in the orders didn't add up. Six of the generals listed in the orders were commanding only a single division. To make the numbers fit, McClellan came to the conclusion that Longstreet and Jackson were actually commanding two very large "grand corps". With this in mind, the force in front of him at Turner's Gap, one of the passes through the South Mountain chain, was considered by the Young Napoleon to be about 30,000 strong, with another 70,000 Rebels waiting for him at Boonsboro. McClellan advanced far more cautiously than was warranted given the reality of the situation, as shown in the orders themselves.
McClellan finally moved on the information on September 14th, at day break, 18 hours after receiving the order. He made no attempt to shift his forces with a night march on the evening of the 13th. He didn't tell his corps commanders about the order, nor did he caution them to move with stealth so as to surprise the Confederates. He had his right wing, under Burnside, move on the Fox's Gap and Turner's Gap passes. The idea was for Burnside's wing to cut the Confederates in two. McClellan ordered Maj. Gen. William Franklin's Sixth Corps to take the southern Crampton's Gap pass and move to relieve Harper's Ferry. (What's interesting is that Franklin's corps had less than 20,000 men, yet McClellan assumed they would be sufficient to relieve the Harper's Ferry garrison in spite of the supposed — and inflated — force opposing them.) The Young Napoleon still held the upper hand, but he had lost valuable time.
The town of Harper's Ferry sits on a v-shaped spur of land pointing westward, at a fork where the Shenandoah River meets the Potomac River. To the northeast is Maryland Heights, the south edge of Elk Mountain, which dominates the town. South of the town is Loudoun Heights, which also overlooks the town. Behind the town, in the open part of the "v" is Bolivar Heights.
The Yankee garrison at Harper's Ferry was under the command of Col. Dixon Miles. Miles was almost thrown out of the army for drunkenness after First Bull Run. His subordinates thought him stubborn and afflicted by a "mental dullness" evident in his failure to meet the threat to the town. The key to the town's defense was Maryland Heights. McClellan and Halleck proposed that Miles should move his garrison onto the Heights and hold out there for as long as they could. There was no water on the mountain, though, and Miles had failed to have cisterns built. Halfway up the Heights was a powerful artillery battery of 2 9-inch Dahlgren rifled guns, a 50 pound Parrott rifled gun, and 4 12-pound smoothbore pieces. They were aimed to protect the approach to the city from the south and west, but were useless in protecting the approach to the Heights itself from the north. Miles did nothing to fortify Solomon's Gap, the only approach to the Heights. The only fortification was a crude, and inadequate, log breastwork.
Instead of defending the Heights with his whole garrison of 13,000 (including those from Martinsburg under Brig. Gen. Julius White, who followed military protocol by putting himself under Miles' command), Miles placed only 1600 men on the Heights. These consisted of men from four regiments. The 32nd Ohio were the only ones with combat experience. The 126th New York had been in the army for all of 21 days. The rest of the garrison sat in an entrenched position on Bolivar Heights.
On September 13, McLaws sent the brigades of Joseph Kershaw and William Barksdale to take Maryland Heights. The Federal pickets ran back to the breastworks just ahead of the attacking Rebels. The first volleys unnerved the 126th New York, but the Ohioans held fast. The 126th's colonel, Eliakim Sherrill, stopped his men from fleeing and put them into a rough battle line, but when another volley saw a bullet hit him in the face and dropped him writhing on the ground with a ghastly wound, the 126th routed. The 32nd Ohio held out as long as they could, but with Miles refusing to give them reinforcements, they were forced to pull off the Heights and return to the town. The guns on the Heights were spiked and thrown into the river, and the men retreated over a pontoon bridge and into Harper's Ferry.
Presently, Jackson arrived on the scene with his divisions prepared to directly assault Bolivar Heights. As McLaws men stood alone on Maryland Heights, Walker's two brigades climbed Loudoun Heights. Miles' garrison was surrounded.
Fate, which had gone against Lee that day, swung slightly in his favour. McClellan had been entertaining local townsfolk when he received the Lost Order. One of the visitors, a Marylander with Southern sympathies, saw the resulting commotion at the Yankee headquarters. Although he knew nothing about the order, he assumed that intelligence data of some sort was presented to McClellan. He went through the Union lines and informed Lee of what he saw. Around noon on September 13, before the order was found, Pleasanton's cavalry — backed with infantry from the Ninth Corps — pushed Stuart's cavalry screen back to Turner's Gap. McClellan had sent the Kanawha Division under Brig. Gen. Jacob Cox to Middletown in support. When Lee heard of this from Stuart around 10 p.m. (and possibly with supporting observations from the Marylander who was at McClellan's headquarters) he linked the two events. He assumed McClellan had received some information and had started to move with more decisiveness.
Lee conferred with Longstreet. This new movement by McClellan could be an attempt to lift the siege at Harper's Ferry. Longstreet urged caution and suggested that the army should combine at the crossroads town of Sharpsburg. Lee didn't want to give up Harper's Ferry so close to its capture, and moving back to Sharpsburg would mean giving up his plan to secure his supply line and draw the Army of the Potomac into a battle in the Cumberland Valley. Instead he ordered Longstreet to prepare to march at dawn to Boonsboro to support D. H. Hill. Longstreet protested that his men would be too tired to be of much help, but Lee insisted.
Daniel Harvey Hill received Stuart's report before Lee and had posted one of his brigades — Brig. Gen. Alfred Colquitt's — in Turner's Gap as a precaution. Now Lee ordered Hill to go to Turner's Gap in the morning and plan its defense with Stuart. Stuart was ordered to hold the gap "at all hazards". McLaws was warned of a potential attack on his rear by McClellan while Jackson was urged to speed up the capture of Harper's Ferry.