CHAPTER 8

MCCLELLAN TAKES THE OFFENSIVE

SEPTEMBER 2–14, 1862

THE ASSUMPTIONS THAT LED LEE TO DIVIDE HIS COMMAND WERE reasonable but erroneous. Lee misjudged the temper of the Union army, which was not demoralized by Pope’s defeat, and also the speed and effectiveness with which McClellan would reorganize his divisions and prepare a field army for operations.

In the brief period between his restoration to command and Lee’s crossing of the Potomac, McClellan had justified Lincoln’s belief in his peculiar skills. His revival of the army’s morale began with his assumption of command on September 2. With his staff behind him he rode out from Alexandria toward Centreville and crossed paths with Generals Pope and McDowell. Although neither had yet been formally relieved of command, they were leaving an army that regarded them with distrust and dislike. McClellan dismissed them with a salute and rode on. Staff officers rode ahead announcing his second coming to the Army of the Potomac, and the columns of tired and discouraged troops erupted in cheers and rejoicing. As one officer remembered,

Shout upon shout went out into the stillness of the night; and as it was taken up along the road and repeated by regiment, brigade, division and corps, we could hear the roar dying away in the distance. The effect of this man’s presence upon the Army of the Potomac—in sunshine or rain, in darkness or daylight, in victory or defeat—was electrical, and too wonderful to make it worth while attempting to give a reason for it.¹

It was indeed a magical moment, remembered as such by the soldiers as well as McClellan himself. The men recognized his jaunty figure as the embodiment of a soldierly ideal to which he himself had taught them to aspire.

The soldiers’ feeling for McClellan and their familiarity with army routine made the task of restoring order much easier than it had been after First Bull Run. But there was more at work than McClellan’s charisma. Washington now had ample facilities for bivouacking and resupplying the men. McClellan had long ago established an effective system of provost guards to round up stragglers, and the veteran regiments had their own well-used means of restoring discipline and establishing well-ordered encampments. The turnabout in army morale also registered the fact that their recent defeat had not been as demoralizing as the Union leadership feared or Lee hoped. Most of these men were veterans who had learned how to estimate the merits of their own performance. Their sense of Second Bull Run was that they had fought well but that their generals had misled them. They appreciated McClellan’s virtues but did not hero-worship him. Those who had served on the Peninsula knew him to be capable of failure and understood that he had limitations. Still, with McClellan in charge they would not have to fear the kind of high-risk blunders of which Pope was guilty; and they knew he would do his best to see that they were kept healthy, well fed, and even well rested.

McClellan would also have to figure out how to make immediate use of the half-trained newly recruited regiments that had been arriving in the capital for the past two months. Anticipating this problem even before he left the Peninsula, he had already requested and received authority to assign these new regiments to existing veteran brigades without regard to their state affiliation. The idea was that the veteran outfits would teach the rookies by example and experienced brigade commanders would know how to make use of raw troops. State governors resisted the change because it limited their power to influence the appointment of brigade level officers. For once, professional wisdom overrode politics.²

On September 5, as the Confederates were crossing the Potomac, McClellan was ordered to assemble a large field army and assume command of its active operations. The task presented serious difficulties. Only three army corps (II, VI, and XII) were relatively fresh, having missed Pope’s debacle. McClellan would have to augment this force by culling from the defeated troops gathered in Washington. He would also have to integrate units, general officers, and staffs from Pope’s army and his own. The personal and political antipathies that had divided Pope’s loyalists from McClellan’s acolytes were now augmented by grievances born of the recent defeat: the suspicion in Pope’s army that McClellan had deliberately allowed them to be beaten; the anger among McClellanites that Pope had wasted their lives and their valor and blamed their generals for his own ineptitude. Among the rank and file, McClellan’s veterans showed disdain for the lackluster record of Pope’s men, who resented the aspersion of their courage.

McClellan’s integration of the Armies of the Potomac and Virginia was part reorganization, part purge. He kept Porter, Sumner, Franklin, and Heintzelman in command of the corps they had led on the Peninsula (V, II, VI, and III), though Heintzelman’s Corps was too badly damaged to take the field. Pope’s Corps commanders, McDowell, Sigel, and Banks, were relieved, and the politically powerful Banks was mollified by appointment to command of the Washington garrison.

Franklin and Porter were longtime friends and supporters of McClellan. Both were well tried by combat on the Peninsula. Franklin had shown competence in command of VI Corps, though he did not move his units with energy or speed. Porter was the best of the corps commanders in large-scale combat. His V Corps had borne the brunt of the fighting throughout the Seven Days, and for part of the time during McClellan’s absence Porter had effectively commanded the whole army. It was not certain that all of his corps could take the field, because it had taken heavy losses at Second Bull Run; but McClellan relied heavily on Porter’s advice and would insist that Porter and the division of Regular Army units from his V Corps go with him into the field.

Major General Edwin Vose Sumner commanded II Corps, the strongest in the army: nearly eighteen thousand veteran troops under experienced division and brigade commanders. Sumner was brave to a fault but as a corps commander utterly out of his depth. Born in 1797, at sixty-five he was the oldest man to serve as a field general in the Civil War, and his understanding of tactics, which may never have been acute, was long out of date. His nickname was “Old Bull Head,” which aptly describes his courage and his intellectual limitations. His virtues had been well displayed on the Peninsula. At Seven Pines and again during the Seven Days he had saved the army from disaster by marching to the sound of the guns, orders and obstacles be damned. The problem was that once engaged he had no judgment, no grasp of the situation beyond what his eyes could see, no understanding of how the action in front of him related to the battle or campaign as a whole.³

McClellan promoted Major General Joseph Hooker to command McDowell’s Corps, now renumbered I Corps. “Fighting Joe” Hooker was forty-eight, fair, floridly handsome, and clean-shaven, with a reputation for bravery, unscrupulous ambition, and a rakehell social life. He had graduated from West Point in 1837 and had prewar combat experience against the Seminoles and in Mexico, but he had left the army in the 1850s for an unsuccessful fling at farming in California. Lincoln commissioned him as brigadier general right after Bull Run, and McClellan put him in command of a division in the III Corps. Hooker earned his nickname during the Peninsula campaign, as he led his division with dash and efficiency in several major engagements. While his courage and competence as a combat general were never questioned, Hooker had a well-earned reputation as a striver and schemer for personal advancement. Although he was not a Radical in politics, he had developed a close relationship with Secretary Chase, who would become his backer in his quest for army command.

Sigel’s and Banks’s troops became the Army of the Potomac’s XI and XII Corps. The former would remain in the Washington defenses when the army took the field. The latter would be temporarily led by Brigadier General Alpheus Williams, the senior division commander, until a major general could be found to fill the appointment. Williams was fifty-two, and his most striking physical characteristic were the magnificent mustachios that swept out nearly a foot to either side above his grizzled chin-beard. His only prewar experience was in the Michigan state militia, but he had actually performed quite well as a division commander.

General Burnside retained command of IX Corps. Two of his divisions under Brigadier General Jesse Reno had suffered in Pope’s defeat. Reno had graduated with McClellan in the Class of 1846 and had remained an artillery officer in the Regulars until the Civil War. He had led a brigade and later a division in Burnside’s North Carolina campaign, where he proved his competence in small-scale actions. At Second Bull Run he had handled his two divisions well under the impossible conditions produced by Pope’s incompetence and managed their retreat without letting them become disorganized.

Burnside also gained two fresh divisions. One had served in his North Carolina campaign, and the other was the “Kanawha Division,” which had operated independently in West Virginia under the command of Brigadier General Jacob Cox. Cox was thirty-four, another amateur soldier who had proved he could learn on the job. He had studied for the ministry at Oberlin, a college noted for its radical experimentation with both religious doctrine and social reform, and became a committed abolitionist. Instead of the ministry, Cox pursued a career in law and politics, served as a militia officer, and became a Republican political leader in the state of Ohio. He served efficiently under McClellan in West Virginia and won a general’s star, and, despite his politics, McClellan had entrusted him with important field commands. Nevertheless, he had no experience in the command of large forces in combat.⁴

McClellan also tried to remedy the misuse of cavalry that had marked his own operations as well as Pope’s. He regrouped regiments that had been scattered among various division and corps commands in a unified division under Brigadier General Alfred Pleasonton and sent them out to probe Lee’s position at Frederick. Pleasonton was one of McClellan’s inner circle of friends and supporters, an experienced cavalry officer who had served in that arm on the frontier and in Mexico after graduating from West Point in 1844. The new organization would eventually allow the Union cavalry to develop into a powerful military instrument, even if, for the present, it was unable to pierce Jeb Stuart’s cavalry screen. McClellan’s military intelligence was therefore as bad as ever. On September 7 Pleasonton reported that Lee had thirty thousand men at Frederick and another sixty thousand sweeping north and east to capture Baltimore, and that General Bragg with another forty thousand was rumored to be in the Shenandoah. The next day Pleasonton reported, on the basis of unreliable civilian observations, that Lee had a hundred thousand troops and was about to invade Pennsylvania.⁵

While Lee’s entire force cannot have been larger than seventy-two thousand and Bragg’s army was in east Tennessee, preparing to invade Kentucky, Lee’s invasion fostered the illusion of a triumphant Confederate grand army riding the crest of victory. The result was panic among civilians throughout the northeast. The governors of Pennsylvania and Maryland called out the militia and stridently demanded protection from Washington. Pennsylvania Governor Curtin appealed directly to McClellan, bypassing the War Department. McClellan reassured the governor that if the Rebels did menace his state, “I shall act with all possible vigor.”⁶

McClellan did move promptly, albeit cautiously, into the field. With only fifty-five thousand troops available for immediate service, he had good reason to be cautious. His field force was indeed outnumbered by the Confederates—though not as badly as Pleasonton led him to believe. An equivalent number of troops remained behind in the Washington fortifications, including his own III and V Corps, and the XI Corps.⁷

McClellan spread four army corps in an arc across the western approaches to Washington: Franklin’s VI Corps on the left, closest to the Potomac; Sumner’s II and the XII Corps from Pope’s army in the center; and Burnside’s IX Corps holding the right, or northern, flank, the critical post if Lee should move on Baltimore. On September 10, Federal cavalry, with infantry backing, probed Confederate positions in front of Frederick, and McClellan learned that Lee’s troops were pulling out of the town—most retreating westward, and some units apparently returning to Virginia. The administration wanted him to take the offensive and at least force Lee to retreat across the Potomac. But McClellan refused to advance beyond Frederick unless the Harpers Ferry garrison was put under his command and the V Corps added to his field force. These requests for reinforcement were perfectly justified if McClellan was to meet Lee’s army on equal terms. Although Lee had far fewer than the 100,000 troops with which McClellan credited him, it would require a force of 75,000 or more to mount an offensive campaign against the Army of Northern Virginia. Even so, Lincoln and Stanton’s mistrust of McClellan, and Halleck’s jealousy of his command privileges, made them reluctant to meet McClellan’s demands.

AN ATMOSPHERE THICK WITH TREASON:
THE WASHINGTON FRONT

SEPTEMBER 3–11, 1862

The mistrust was mutual. To McClellan the menace of Lee’s army at Frederick was again of less immediate concern than the malevolence of his enemies in Washington. He believed that Pope’s disaster and his sudden recall to command were signs of a reversal in the tide of his political fortunes. His reputation as the nation’s chief military reliance, its Great White Hope, was confirmed. The menace of Lee’s invasion had made the administration feel its dependence on his military genius. His first impulse after being restored to command was to use the opportunity to finally stage his palace coup: he would refuse to save Lincoln unless the president agreed to purge Stanton from the cabinet. While Burnside had talked him out of making a move so blatantly political, in the days following McClellan’s assumption of command his officers and political supporters intensified their campaign to win for McClellan greater control over civil and military policy.⁸

McClellan’s headquarters had become a protective bubble, almost impenetrable by people whose ideas differed from McClellan’s, let alone by actual critics. A perimeter defense manned by aides restricted access to the commanding general, admitting his military supporters, friendly journalists, and political allies, denying entrance not only to agents of the administration but even to military officers whose views or presence he had no use for. His inner circle of staff officers had been purged of potential critics and lukewarm supporters, and his circle of military confidants was small, and due for further contraction. His chief of staff, General Marcy, was also his father-in-law. Colonel Thomas Key may have been the most influential of his senior staff—critics considered him McClellan’s “evil genius,” for advice that maximized the general’s ties to conservative Democrats.⁹ Among the corps and division commanders, Franklin was a strong and loyal ally, and Fitz-John Porter, as we have seen, his most trusted confidant. At the moment Generals Burnside of IX Corps and William “Baldy” Smith, now division commander in VI Corps, were considered friends and allies. But Burnside had spoken against McClellan’s ultimatum against Stanton, and Smith had expressed reservations about McClellan’s political connections, and both would soon find themselves outcast from the general’s circle. In the daily life of his headquarters, whether established in some large house or in tents in the field, wherever McClellan turned he heard his own opinions praised and repeated, felt his own angers and grievances as emotions shared and affirmed by all with whom he came in contact. He lived in a hall of mirrors. As he told his wife on September 7, “I have now the entire confidence of the Govt,” by which he meant Lincoln, “& the love of the army . . . my enemies are crushed, silent & disarmed—if I defeat the rebels I shall be master of the situation.”¹⁰

Public opinion did appear to be moving in his direction. James Gordon Bennett’s New York Herald hailed McClellan’s reappointment as the start of a “New Order of Things.” The repulse of the Rebel invasion was now certain, and the country could rest assured that the war policy of Lincoln’s administration would take a conservative direction. Bennett praised Lincoln’s “firmness” in sustaining McClellan, which was “a death blow to the meddling radicals” and the “howling dervishes of abolitionism.”¹¹ Manton Marble of the World was no less pleased, though his praise of McClellan was tempered. “We congratulate the nation!” he wrote on McClellan’s restoration to command. “He may not have the genius of a Napoleon” but he is preferable to the “pseudo-Napoleons” lately in command, and in his hands “the capital is safe” and the army assured of prudent use. Marble then went on to strenuously condemn Stanton and the Radicals for their “slurs on Gen. McClellan and his mode of conducting the war.” History would record with “amazement and shame” that such scoundrels should ever have been heeded. “The President, the army, the whole country stand aghast at the results of the system into which [Lincoln] deviated under pressure of the radicals against General McClellan.”¹² Even the Republican New York Times took a favorable view of his ascension. Only Greeley’s Tribune warned the president “not to lean upon broken reeds, nor to pamper incompetency, nor rely upon imbecility, in the execution of its decrees.” The people would not forgive the president if he grew timid about “hurting, despoiling, or even exterminating Southern traitors, or of offending their secret coadjutors in the North.”¹³

All of the actors in this political drama—Lincoln and McClellan, the cabinet and the army staff, the congressmen and newspaper editors and party notables—moved in an atmosphere still “thick with treason,” or with accusations of treason, which under the circumstances were nearly as dangerous to republican government as treason itself. With a civil war raging, political hysteria rising, and the enemy at the gates of the capital, the expectation of treason might drive patriots to actions that verged on revolution. The proposal made on September 2 by Chase and Stanton, that McClellan receive “summary justice”—Chase said he should be shot—would have been akin to the guillotining of generals by the Jacobins during the French Revolution’s Reign of Terror. When McClellan fulminated against the traitors and fools in the government, and fantasized about assuming the dictatorship or marching on Washington, his staff officers and senior generals, and his political backers, inevitably began thinking about when and even how such an action should be attempted, and a Napoleonic overturn of the American republic became imaginable.

Rumors were rife that a military putsch was in the offing. On September 13, George Templeton Strong, a wealthy New York Republican, noted in his diary, “A new and most alarming kind of talk” among the more pro-Southern Democrats in the City, to the effect that McClellan was planning to confer with former colleagues turned Confederate generals, to arrange a compromise peace which the military would then “enforce” on the two governments. On September 10 Senator Henry Wilson of Massachusetts, chairman of the Committee on Military Affairs, told Navy Secretary Welles that McClellan’s staff were conspiring “for a revolution and the establishment of a provisional government.” Welles dismissed Wilson as an alarmist but was deeply troubled that McClellan had made his army into a political power base whose values and purposes were at odds with those of the elected administration, “a spirit more factious and personal than patriotic.” Welles believed McClellan meant to “use [the army] for his own purposes—an informant who had been privy to one of McClellan’s early conferences with S. L. M. Barlow recalled McClellan saying that he “would pursue a line of policy of his own, regardless of the Administration, its wishes and objects.” Lincoln himself agreed that there had indeed “been a design, a purpose in breaking down Pope, without regard of consequences to the country. It is shocking to see and know this; but there is no remedy at present, McClellan has the army with him.”¹⁴

The most explicit threat of a military coup was passed to reporter Nathaniel Paige of the New York Tribune by Colonel Thomas Key, the so-called evil genius of McClellan’s staff. On September 11, as the army was bivouacking near Frederick, Key told Paige that some of his colleagues were planning to “change front on Washington” to compel the government to abjure its “abolitionist” sentiments, and thus open the way to a negotiated peace, which might recognize some form of Southern independence. These officers were, said Key, “fighting for a boundary line and not for the Union.” Key swore that McClellan knew nothing of this and would have rebuked it if he had known. However, instead of informing McClellan, Key was leaking this information to a reporter for a paper that was Radical in sentiment and so hostile to McClellan that it had recently accused him of imbecility and disloyalty. Key might have been acting in good faith, seeking to warn the administration of its danger while still protecting McClellan’s standing. He also might have been attempting to pressure the administration to follow McClellan’s lead or face a military uprising.¹⁵

Horace Greeley evidently heard the threat and took it seriously. On September 12 and 13 the Tribune published a pair of editorials warning of “a conspiracy between the chiefs of the Rebel and Union armies to subvert the Republic and establish a Pro-slavery despotism on its ruins.” Greeley took note of the proclamations made by Lee and Davis, which called for an uprising of Southern sympathizers in support of the Confederate invasion. “Our army has come among you, and is prepared to assist you with the power of its arms in regaining the rights of which you have been despoiled.” He linked this appeal with another issued by Confederate agents in Canada, which suggested that what the Davis government now sought was not separation and independence but an actualconquest of the North—a reestablishment of the Union on a pro-slavery basis. Lee’s invasion was presumably the first step in this conquest. Greeley accused the Herald, along with its audience of “Northern men with Southern principles,” of assisting this project by fomenting “a Military conspiracy culminating in a dictatorship.” The Herald and its claque had repeatedly called for “Gen. McClellan to disperse [Congress] with the bayonet, after the fashion of Cromwell and Bonaparte” if it did not “legislate according to the Pro-slavery programme.” Now they were seizing the opportunity of Lee’s invasion to resume their “diabolical work.”¹⁶

The Cromwell reference was apropos. On September 11 a New York Herald editorial was urging McClellan not only to “insist upon the modification and reconstruction of the cabinet, in order to have it purged of the radical taint which may again infuse its poison over the whole,” but to demand on his own account “indemnity for the past and security for the future.” The latter implied some formal acknowledgment by the administration that it had been guilty of mistreating McClellan in the past, and a guarantee that his present elevation to command would not be rescinded. The Herald insisted such an assertion of personal power was justified, because “[t]he safety of the country is entrusted to him,” and he is therefore entitled to destroy the “insidious enemy” in his rear, which threatens to disrupt his plan of campaign.¹⁷

Stephen Sears, whose studies of McClellan’s career are both thorough and highly critical, has concluded, “It cannot be imagined that George McClellan would have lent himself to a military coup.” However, there is ample evidence that McClellan’s closest colleagues were actively imagining that very thing, and that the atmosphere of McClellan’s headquarters allowed the possibility of a coup to be freely entertained. Even if the call to “change front on Washington” did not reflect McClellan’s actual plans, it reflected beliefs and desires he had often expressed. Those who openly discussed the matter certainly did so in McClellan’s interest, and if not on his instructions then almost certainly with his knowledge. In a time of crisis and an atmosphere of treason, with aggrieved officers and armed men thronging the capital, it was a dangerous suggestion to make.¹⁸

THE LOST ORDER, SEPTEMBER 11–13, 1862

Military victory offered McClellan a clearer, cleaner, and more certain path to power than a coup at Washington: “if I defeat the rebels I shall be master of the situation.” Still, he could not defeat Lee’s army by standing on the defensive in the Washington suburbs while Confederates ravaged the countryside and raided into Pennsylvania. Some kind of counter­offensive had to be undertaken. It would be extraordinarily risky to confront Lee’s “superior” force in a general engagement, but he could count himselfvictorious if he merely compelled Lee to abandon his invasion and retreat to Virginia. If he kept his forces well concentrated and properly positioned they could repel any attack Lee might make and impose losses serious enough to force a Confederate withdrawal, while not risking a decisive battle. Even a campaign of maneuver might induce Lee to retire without a fight—he could not stay indefinitely north of the Potomac with a concentrated Army of the Potomac dogging his heels. So despite the weakness of his force, of which he was painfully aware, and Lee’s strength (which he grossly overrated), McClellan was more than willing to “act with all possible vigor.”¹⁹

While Lee remained at Frederick, McClellan was uncertain whether to prepare for an opportunistic advance or a desperate defense. When he learned (on September 10) that Lee’s forces had pulled out of Frederick, and that part of Lee’s army (Walker’s Division) had returned to Virginia, McClellan ordered his entire force to advance and called for reinforcements that would allow him to pursue and strike an enemy that might be on the retreat. On September 11, he wrote Halleck that he was opposed by a “gigantic rebel army” of 120,000 men, and though he was willing to confront that army with his own inferior force he was doubtful of the outcome and feared that “if we should be defeated the consequences to the country would be disastrous in the extreme.” He therefore renewed his request for the Harpers Ferry garrison and at least one of the three army corps currently reorganizing in Washington.²⁰

The Confederate army was moving west and away from Washington, clearly designing to pick off the garrison at Harpers Ferry. Such a move could either indicate a general withdrawal into Virginia via the upstream fords of the Potomac or be a mere preliminary to the renewal of offensive action out of western Maryland. As he advanced toward Frederick, McClellan was still expecting Lee to turn and attack him. He told his wife that he expected “to fight a great battle,” but it would be a defensive one: “I do not think the secesh will catch me very badly.” To Halleck he wrote that he thought himself safe unless attacked by “overwhelming” force; and when Halleck urged him to beware of an attack on Washington, McClellan answered that a defeat to his army would be far more dangerous to the nation than the loss of the capital. Aside from exposing the fact that McClellan still identified the national cause exclusively with his own fate and that of his army, these dispatches indicate that, as late as September 11, McClellan thought defensive operations more likely than an offensive.²¹

However, on that most eventful day McClellan received word that Lincoln had acceded to his requests: Harpers Ferry was now under his command (too late for that to do any good), and two divisions of V Corps led by the loyal Fitz-John Porter were marching to join him at Frederick. No other reinforcement could have been so gratifying to McClellan. Porter was his staunchest ally, and in sending him forward Halleck was also setting aside the charges that had been filed against Porter by John Pope.

McClellan also received reports (mainly from civilian sources) that seemed to indicate Lee might be planning to retreat into Virginia. They confirmed the news that Lee’s main body had gone west, passing over both Catoctin Mountain and the longer, higher ridge of South Mountain, to Boonsboro; that some troops had already returned to Virginia (this was Walker’s Division, marching on Harpers Ferry); and that a large column (it was Jackson’s) had recrossed the Potomac well upstream from Harpers Ferry. It was possible that Lee’s army was “skedaddling,” as he wrote to Mary Ellen. It was certain that Lee’s army was divided, but the proportions were unknown, and the fact that Lee had risked such division was an indication of his army’s superior strength.

Nevertheless, McClellan for once seemed determined to strike a blow. Buoyed by these reports, by reinforcements, and by the evidence they gave of his power with the administration, McClellan began to consider an offensive that would rescue Harpers Ferry and “catch” Lee’s army before its elements could recombine or recross the Potomac. On September 13 McClellan ordered Pleasonton’s cavalry, with a division of Burnside’s IX Corps infantry behind it, to break through the Confederate cavalry defending the passes through Catoctin Mountain and find out where and how Lee’s army was positioned.

Those operations were already under way when a dispatch arrived at his headquarters from General Alpheus Williams, temporarily commanding the XII Corps. An enlisted man, Corporal Barton Mitchell of the Twenty-seventh Indiana, had found an envelope lying on the ground that contained three cigars and a copy of Special Order No. 191, issued by General Lee on September 9, which laid out in detail the planned movements of Lee’s divided army over the past five days.

The finding of this lost order was a turning point in the campaign and an event so unlikely, and so charged with ironies, that it has become historical legend. It was an unearned intelligence coup for McClellan, whose generalship was marked by abysmal incompetence in gathering and handling intelligence. It was a catastrophic piece of bad luck for Lee, which wrecked his plan of campaign and gave the cautious and slow-moving McClellan the confidence to assume the offensive and advance with greater energy and determination than he had ever shown.

McClellan got his hands on the orders late in the morning of September 13 and instantly recognized the opportunity they afforded to catch and defeat Lee’s army. He dashed off a dispatch to Lincoln at noon in which he boldly declared, “I have all the plans of the Rebels and will catch them in their own trap if my men are equal to the emergency. I now feel I can count on them as of old.” He told the president that the army was already in motion “as rapidly as possible.” It is evidence of his exalted self-confidence that he would promise so much to a president who always demanded more speed and harder fighting than McClellan was willing to deliver. When General John Gibbon, commander of I Corps’ “Iron Brigade,” stopped in at headquarters later that afternoon, McClellan told him that Lee had committed a serious blunder in dividing his army and that with that information, “if I cannot whip Bobbie Lee, I will be willing to go home.” If Gibbon and his comrades would give him two days’ hard marching he would “pitch into [Lee’s] centre” while his army’s wings were divided, the way Napoleon I had beaten the Austrians at Castiglione in 1796.²²

In his conversation with Gibbon, in his telegram to Halleck, and in the orders he later issued to Franklin, McClellan declared his intention to achieve a “decisive” result. That word “decisive” seems to imply an intention to seek a Napoleonic triumph, in which the opposing army is virtually destroyed and the war effectively won. Gibbon certainly understood it that way: after speaking to McClellan, Gibbon told his men that they would soon get the Rebels “in such a tight place they could never get out.”²³

But McClellan had a different understanding of what, under the circumstances, would count as decisive victory. It is telling that he used the Battle of Castiglione as an analogy to his current operation. In that campaign Napoleon’s army, besieging Mantua, was outnumbered by Austrian forces advancing to the city’s relief. Napoleon maneuvered deftly to keep the Austrian forces divided, then concentrated a superior force to defeat the largest relief column at Castiglione. However, the result was neither tactically nor strategically decisive. Castiglione merely compelled one Austrian relief column to retreat. The siege would continue for six months, during which Napoleon had to fight seven more general engagements to repel Austrian relief operations.

From McClellan’s perspective, any action that compelled Lee’s invading column to retreat from Maryland would be “decisive,” because it would confirm his standing as the indispensable man and enable him to become “master of the situation” in the ongoing struggle to control Lincoln’s administration. If he could confront Lee at Boonsboro before Jackson could complete his conquest of Harpers Ferry, he would compel Lee to choose between fighting McClellan’s superior force and a withdrawal to Virginia. Knowing what he himself would do in Lee’s place, McClellan was drawn to the thought that Lee would retreat—hence his supposition that he might have to “catch” Lee before he got away.

McClellan would still have to guard against Lee’s boldness. The lost order was four days old, and in that time Lee might well have altered his plans. Intelligence had indicated there were large enemy forces at ­Martinsburg—were these new troops, or was this merely belated news of Jackson’s Corps? If the latter, were they en route to Harpers Ferry or poised to rejoin Lee? To the cautious McClellan it was inconceivable that Lee would have so divided his army unless he had indeed disposed of superior forces. The 120,000 estimate he reported to Halleck had no basis in any report from scouts or informants, and it significantly, perhaps purposely, exaggerated the estimate of 100,000 reported by Pleasonton. However, even at Pleasonton’s estimate, McClellan’s total strength of about 75,000 was weaker than Lee’s. According to the lost order at least half of Lee’s army was concentrated at Boonsboro, twenty miles away by the National Road from Frederick. To assail it, McClellan’s troops might have to first fight their way through the passes of Catoctin Mountain, and then through the steeper, narrower passes of South Mountain, ideally suited to defense. Moreover, McClellan could not throw his whole force against Boonsboro. He had to send a large detachment to the relief of Harpers Ferry, using a separate and parallel route of march twelve miles to the south. That would leave him fewer than sixty thousand to oppose Lee’s estimated fifty-plus thousand in a strong defensive position. If Lee’s force held out, Jackson might be able to rejoin him. Their united force would considerably outnumber McClellan’s, who would then have to choose between defeat by superior forces or ignominious retreat—neither of which would make him “master of the situation” in Washington.²⁴

McClellan’s dispatches to Halleck reflected his ambivalence. At 8:45 PM on the thirteenth he assured Halleck that the whole of Lee’s army was before him and added: “Will soon have decisive battle.” Three hours later, his detailed report was far more circumspect. Although he enjoyed the advantage of knowing how Lee’s force was divided, “they outnumber me when united.” He was moving to relieve Harpers Ferry and expected “a severe engagement tomorrow” but warned Halleck that “we may be too late.” It was vital that Halleck understand that, though he did not “undervalue” the safety of Washington, “upon the success of this Army the fate of the nation depends.” It was a restatement of the fundamental premise of McClellan’s strategy: that the Army of the Potomac must not risk a serious defeat. If he had earlier oversold his prospects of triumph to Lincoln, he was now underselling them to Halleck.²⁵

McClellan’s operational orders reflected a sort of judicious daring. For his own reasons he knew he had to take the offensive, and so for the first time he showed a willingness to meet Lincoln’s requirement that field commanders use their available force, whatever the risk, to achieve necessary military goals. His plan was to attack a detachment under Lee that he believed was not much weaker than the numbers he could bring against it. He would advance more boldly, with greater speed and urgency than ever, yet still at a measured pace that would keep his forces concentrated for mutual support.²⁶

His army would advance in two columns. McClellan himself would command the main force, which would follow the National Road from Frederick to Boonsboro, crossing South Mountain at Turner’s Gap. The cavalry would lead, backed by the Kanawha Division commanded by Brigadier General Jacob Cox, recently attached to IX Corps. The rest of IX Corps would follow, with Hooker’s I Corps coming up behind it. McClellan assigned Burnside to command this advance force (between 25,000 and 28,000), while McClellan brought up the XII, II and V Corps (30,000). With luck this force might catch Longstreet’s wing with its elements divided and defeat it in detail. Failing that, McClellan would at least hold Lee’s strength in front of Boonsboro and prevent his interference with the relief of Harpers Ferry.

In a strategic sense, the relief of Harpers Ferry was the most critical aspect of the operation. If it succeeded it would save 13,000 troops from capture while also potentially giving McClellan the chance for a substantial, perhaps even a decisive, military victory over the separate components of Lee’s army. Conversely, if the relief failed and Jackson seized Harpers Ferry, Lee might be able to reunite his army and confront the Federal army with what McClellan believed were superior numbers. The relief column was entrusted to Major General William Franklin, his old friend and supporter, who commanded two divisions of the VI Corps (13,000) camped just south of Frederick, and a division transferred from IV Corps (6,500), commanded by Brigadier General Darius Couch, which was still some distance behind. McClellan wanted Franklin to cross Catoctin Mountain south of the National Road, then strike for Crampton’s Gap in South Mountain. If his corps broke through the gap, Franklin could then turn south to attack McLaws’s command, which, as the lost order showed, was the only part of Jackson’s Corps north of the Potomac.²⁷

Although McClellan was committing his whole force to the offensive, he also hedged against the risks he was assuming by enjoining Burnside and Franklin to advance with caution. His orders to Burnside were given orally, but the written orders to Franklin indicate the balance between boldness and anxiety that shaped his tactics. He told Franklin he intended to “cut the enemy in two & beat him in detail” by striking Boonsboro quickly and in strength. No considerations “should for a moment interfere with the decisive results I hope to gain.” A degree of urgency was suggested by McClellan’s unwonted demand that they march at daybreak—a more energetic commander might have had them march that evening, even though a night march is more difficult and risky. Nor did McClellan demand that they push their commands forward by forced marches. Instead, McClellan warned Franklin to keep his troops well concentrated, “prevent straggling & bring every available man into action” lest the Confederates surprise him with one of those rapid concentrations at which Lee and Jackson were so adept.²⁸

The ambiguity in these orders is significant. McClellan knew that Franklin was characteristically slow in conducting operations—so much so that McClellan had complained to his wife about it, and considered relieving him of command. Knowing that, McClellan still did not urge Franklin to move with speed but rather encouraged caution and circumspection. The pace of Burnside’s column was similarly regulated to allow its elements to close up for mutual support.

McClellan, moving more aggressively than ever before, had to take what advantage he could of the situation exposed by the lost order. Nevertheless, his aggressive intent was modulated by the fundamental principle that forbade endangering the safety of his own force. He could not catch Lee at a disadvantage at Boonsboro, or break the encirclement of Harpers Ferry, without ordering the advance elements of his command to rush forward and engage the enemy before the main body of the army could come up. But to do that was to expose those detachments to defeat or destruction, and McClellan saw no need to run that risk. If he could confront Lee’s divided force with his own army mostly united, Lee would be compelled to retreat—and that would be victory enough to solidify McClellan’s standing as hero of the hour.

LEE ON THE DEFENSIVE, SEPTEMBER 12–14, 1862

On September 13, Lee was with Longstreet at Hagerstown, tired out by the long journey from Frederick, still suffering from the fall that had disabled him. He had had some notice that McClellan’s army was on the move. On the twelfth, Stuart had informed Lee that Federal troops had occupied Frederick and that he was surprised by McClellan’s relatively rapid advance. The very next day, Stuart reported that Federal cavalry, with infantry support, had broken through the units he had posted on Catoctin Mountain to screen Lee’s withdrawal from Federal observation. Still, Catoctin Mountain was only the first of the two ridgelines that stood between McClellan’s army at Frederick and Lee’s at Boonsboro, and the Federal force that had broken through was not large enough to defeat the defense D. H. Hill’s Division could offer at South Mountain. Lee therefore judged the threat of a large-scale attack was not imminent.

Then at eight that evening, Lee received shocking news. By a coincidence almost as outrageous as the finding of the lost order, a Maryland civilian and Confederate sympathizer had been at McClellan’s headquarters when the dispatch was being read. Although the civilian did not know what the dispatch contained, McClellan’s enthusiastic outcry, “Now I know what to do!,” and the flurry of orders that followed, suggested the find was significant. The civilian rode away and made contact with Confederate cavalry. By five in the evening the news had reached Stuart. Whether or not Stuart guessed that McClellan had seen a copy of Lee’s General Order No. 191, the civilian’s report suggested that McClellan had discovered the division of Lee’s army and was moving to exploit it. The burden of Stuart’s message was confirmed by a report from D. H. Hill, that the valley below Turner’s Gap was filled with the campfires of Federal infantry, indicating that McClellan’s main body was moving against Boonsboro.

Lee’s campaign was now in extreme peril. The vanguard of McClellan’s army was approaching Turner’s Gap, less than ten miles from Boonsboro, in a force large enough to overwhelm Hill’s single division defending the center of Lee’s far-flung army. The nearest reinforcement for Hill was the infantry of Longstreet’s Corps, which was some twenty miles away at Hagerstown. On the map it looked possible for McClellan to smash through Hill’s defense, then turn north to attack Longstreet’s heavily outnumbered divisions and threaten the army’s artillery reserve and supply train. At the same time, the VI Corps might break through Crampton’s Gap to relieve Harpers Ferry. If it did, McClellan’s army would be in position to cut the Valley route that supplied Lee’s army, and to interpose itself between that army and Richmond; and that would compel Lee to either assault the Army of the Potomac head-on or make a desperate march through the West Virginia mountains to get around McClellan’s flank.²⁹

All through the evening of September 13 and late into the night, Lee was intensely engaged in building a clear picture of the tactical situation and developing plans to deal with it. Not only did he need current intelligence on the enemy’s movements, he also needed to find out where the several elements of Jackson’s wing were located and how far they had advanced toward the capture of Harpers Ferry. He had had no reports from Jackson for two days. His requests for information, and the responses, were delayed to the pace of mounted couriers riding over the thirty miles of roads and river fords to Jackson, over twenty or more miles of mountain road to Stuart. As reports came in he had to translate the emerging intelligence into plans of action, and orders, for defending the two most vulnerable points on his line: Turner’s Gap, and McLaws’s position on Maryland Heights.

It was still possible to avoid catastrophe if prompt action was taken to delay McClellan’s advance. McClellan would have to attack through the South Mountain gaps, which were ideally suited to defense. D. H. Hill’s Division, with support from Stuart, was positioned to defend the northern gaps on the roads to Boonsboro. They would have to hold off McClellan’s main body long enough for Longstreet’s infantry to come to their support. With his northern elements reunited at Boonsboro, Lee could fight a delaying action that would enable Jackson to complete the conquest of Harpers Ferry. Should things go badly, Longstreet’s Corps would still have a line of retreat to Virginia, via Sharpsburg and the fords at Shepherdstown.

Lee therefore ordered Hill to defend the South Mountain gaps to the last extremity, and Longstreet to join Hill by a forced march from Hagers­town. Jeb Stuart and two of his three brigades were still in the Turner’s Gap area, and Lee wanted them to stay there and assist in prolonging Hill’s defense. But Lee’s orders were badly worded—perhaps the result of physical exhaustion, the lingering effects of his injuries, and the strain of sudden crisis in the dark of a long day. Stuart thought Lee wanted him to defend Crampton’s Gap, and he rode off southward with his whole command—except for one regiment, the Fifth Virginia, left behind by mistake.

Since the outcome of this defensive operation was most uncertain, Lee also thought it prudent to get the army’s slow-moving wagon train, with its reserves of ammunition and equipment, out of harm’s way. He ordered the trains and the army’s artillery reserve back to Virginia via the six-mile road that ran south from Hagerstown to Williamsport.

Lee was also gravely concerned about the threat posed to McLaws’s Division by VI Corps’ advance on Crampton’s Gap. He had had no reports from McLaws for two days and did not know whether he had succeeded in capturing Maryland Heights or was still embattled on his front and unaware of the threat approaching from his rear. So far as Lee knew, the only defense in Crampton’s Gap was Munford’s cavalry brigade: a few hundred troopers with short-range carbines facing thirteen thousand infantry with heavy guns. If Franklin crashed through the cavalry screen he could wheel south through Pleasant Valley and hit McLaws’s position on Maryland Heights from the rear. If Harpers Ferry was still holding out, McLaws would be isolated and trapped between the garrison and Franklin’s corps.

Lee did what little he could to aid a command with which he was completely out of touch. He sent several dispatches to McLaws, warning of the approaching danger and suggesting possible lines of retreat, by which McLaws could evade Franklin and rejoin the army at Boonsboro or Sharpsburg; but he cautioned that his suggestions were subordinate to whatever orders McLaws might in the meantime receive from Jackson.

MCLAWS’S SITUATION WAS less dangerous than Lee feared, but still precarious. On the morning of September 13, McLaws’s assault brigades had advanced against the Federal defense line on Maryland Heights. Instead of a strong and well-entrenched force of infantry and artillery, they found a scratch force of 1,600 Federals, most of whom belonged to the 126th New York, whose men had only been in uniform for three weeks and had barely learned the manual of arms. The position did hold a powerful artillery battery of three heavy rifled guns and four short-range smoothbores—but they had been posted to fire on enemies approaching via the river valley, and could not be used to defend against an attack from the north. This inadequate and badly conceived defense was the responsibility of Colonel Miles, who had been advised to strongly fortify Maryland Heights and had done nothing about it. When the Confederates charged, the New Yorkers broke and ran, spreading disorder among the troops behind them. The veteran thirty-second Ohio tried to hold the line, but it soon fired away all of its ammunition. Colonel Ford, who commanded the outpost, sent to Miles for reinforcements, to which Miles responded, “You can’t have another damned man. . . . If you can’t hold it, leave it.” Ford spiked his guns and rolled them down the slope, then led his survivors across a pontoon bridge and into Harpers Ferry.³⁰

The loss of Maryland Heights cut off the garrison’s route of escape to the north and was sufficient in itself to make Harpers Ferry untenable once McLaws planted his artillery on the heights. Miles was also hemmed in on the southeast by Walker’s Division, which had seized Loudon Heights, and Jackson’s twenty thousand were approaching from the northwest, threatening to envelop the garrison. Miles concentrated his entire force in a perimeter around the town of Harpers Ferry and established a defensive line on Bolivar Heights. But the position was so tight that every part of it could be swept by Walker’s and McLaws’s guns. Miles did nothing to disrupt Jackson’s deployment, which would bring overwhelming strength to bear against Bolivar Heights.

Nevertheless, despite Miles’s incompetent defensive measures, McLaws’s command was still in some peril. The original garrison of Harpers Ferry was larger than Lee or his generals had anticipated, and the arrival of General White’s command from Martinsburg had raised their number to nearly thirteen thousand. A force of that size, if it had determined leadership, could hold out for days, despite the advantages of number and position enjoyed by the Confederates. Colonel Miles was not a very determined leader, but even he believed that the garrison could hold out for one more day. On the night of the thirteenth he sent a staff officer, Captain Russell, through enemy lines with a message to McClellan, describing his situation and warning that if relief did not reach him first he would have to surrender on September 15.

If Franklin broke through Crampton’s Gap on the fourteenth, and moved swiftly against Maryland Heights, McLaws’s command might well be trapped between the hammer and the anvil.