A Historical Recount of Antietam: Part 1
The Battle of Antietam is the most widely remembered and popular conflict in the American Civil War, and it's not difficult to understand why. The high water mark of the Confederacy, the bloodiest single day in American history, the General's Mutiny - the entire battle is positively dripping with pathos and personalities. Scenes such as the storming of Yates' Bridge are etched into the public's consciousness through dozens of books and movies, the Antietam Adress is quite possibly one of the most well-known speeches given by an American politician ever, Robert E. Lee being forced to evacuate by his own men immortalized in painting and prose. Unsurprisingly, it's also been the subject of much debate, both today and from the moment it happened, as the events at Antietam were of immense political importance and only grew more so with time. It plays a central role in the mythology of the War Between the States, both for the North and South, and is the subject of considerable mythology and alt-history, what-if's and what-could-have-been's endlessly discussed.
With all of the above, in many cases
what actually happened can almost be overwhelmed, and the purpose of this treatise is to lay out the exact events that occurred at the Battle of Antietam, why they happened, and how much of it truly rested on a knife's edge, and how much is that perception myth/wishful thinking?
The Leadup
The first year of the Civil War had largely been one of success for the Confederacy. The Western Front had been a mixed bag and the beginning of the Union blockade was concerning, but the Union's attempt to seize Richmond and bring an early end to the rebellion had ended in dismal failure. In particular, General Robert E. Lee had led his army on a stunning series of successes against McClellan and Pope, sending both fleeing back North in tatters through the Seven Days Campaign and the Second Battle of Manassas. Through this spree of victory, he had won the Confederacy its first real sense of breathing room since the war had begun, and Lee was determined to take advantage of the moment.
There were multiple reasons to take the offensive and attack the North, despite the risk it posed. The simple matter of fact was that the CSA couldn't win the war by sitting back and defending - it needed to force the Yankees to give up and earn foreign recognition, and despite Lee's promising victories neither of those things were happening. The South was severely outmatched in both population and industry - if the northerners were allowed to turn the war into one of attrition, their victory was inevitable. By taking the offensive, Lee believed he would be able to win over the slave states that had sided with the Union (such as Maryland and Kentucky), further rattle the North's populace and undermine Lincoln, as well as prove to foreign interests that the Confederacy's cause was viable, as it had become increasingly clear the 'King Cotton' strategy was not going to work. It would be a risk, but Lee believed the war would be lost for sure by playing it safe, so despite reluctance on the part of the government* and his troops, a significant amount of which would stay behind in Virginia, the AoNV marched north.
(This isn't actually true, Davis fully supported the strategy, but in this ATL Antietam is primarily known as Lee's greatest failure and he is somewhat unfairly considered its sole architect even by historians)
Meanwhile, the Union army was trying to piece itself back together after the disasters of the previous campaigns. They were demoralized, disorganized, and rudderless - and as they soon found out, in a time such weakness could ill be afforded. Word of Lee's invasion soon reached Washington, and President Lincoln came to the realization that he could not potentially afford another Pope taking the reigns. Instead, he turned to General George McClellan. Despite personally disliking the man, Lincoln believed that his popularity with the soldiers and organizational talent would serve to get the army back into fighting shape, and hopefully on the defense McClellan's caution would prove a less inhibiting trait. And indeed, the general set about reforming the army of the Potomac with gusto, eager to validate himself after his (perceived) unjust usurpation from total command after the Peninsular Campaign.
One of the decisions McClellan had to make while reforming the army was the status of the IX Corps, currently under the command of Brigadier General Sebastian Yates, who stood out compared to the rest of his peers, universally army veterans. Yates' only previous military experience, in contrast, was acting as an aide to a Colonel stuck in Texas during the Mexican-American War, and it was frankly through the political connections of his father (a prominent lawyer) that he had been granted command of a Rhode Island regiment. A quintessential political general, in other words, and certainly not an ideal figure to be controlling nearly 20,000 men, the third-largest Corps in the army. That being said, there were also a number of factors speaking in Yates' favor. Most prominently was the fact that there wasn't really anyone suitable available to
replace him - indeed, Yates himself was a replacement for General John Reno, who had fallen ill during Second Bull Run and then fallen off his horse while trying to ride through the sickness. Shuttling in an inexperienced replacement at the last second would be a dubious improvement, and at least Yates knew his men. That being said, there was also Sebastian's combat record, which was actually quite impressive even at the time. His conduct in North Carolina and Second Bull Run had been consistently praised, with Yates showing both tactical insight and personal bravery in several engagements as he climbed through the ranks. Most prominently, however, would be the Battle of Chantilly: tasked to command the Union rearguard after the disastrous clash at Bull Run, the political general led a daring flanking attack on Jackson's exposed forces through a vicious thunderstorm, giving the rebel forces a rough whipping and achieving the only real success Pope saw during his command, a feat for which Yates was lauded in the North's papers despite the limited actual scope of the victory. His conduct was also substantiated by praise from generals who had previously met him, such as Burnside and Kearny.
So despite McClellan's misgivings, in the end he decided to leave Yates in command, hoping that by sticking his Corps under Burnside in the 'Right Wing' of the army any disaster borne from inexperience could be avoided. The Right Wing was something of a dog house, actually, with Burnside being tasked to lead three Corps under Yates, Kearny, and Hooker - all generals that seemed to reside in McClellan's disfavor. Kearny in particular had earned his ire due to starkly different philosophies in leadership and bitter condemnation on Kearny's part over McClellan's actions during the Peninsular campaign, while Hooker was an infamous rank-climber who had opposed McClellan politically and openly desired his position. Ambrose Burnside wasn't necessarily a
friend of the general, but he had strongly opposed Pope's command and was patently unambitious, a cautious general that would cool the hot-heads under his command and not undermine McClellan to any real extent. The rest of the generalship he was more comfortable with, Porter and Franklin especially being close allies while Sumner and Mansfield were old men not viewed as serious threats to his authority.
McClellan still strongly believed himself to be outnumbered by Lee, but with considerable political pressure to prove himself and needing to halt the invasion, he devised an uncharacteristically aggressive strategy to hit Lee while his forces were spread out in the initial stages of the attack, correctly divining that the southern general's aggressiveness would lead him to split his men to hit multiple targets at once. However, worried that too hasty an advance would lead to a defeat in detail and apparently unconcerned with information leaks alerting Lee to the plan, McClellan strongly urged his generals to keep their advance slow, careful, and meticulous.
Burnside, upon receiving these orders, set about discussing strategy with his three major subordinates, and it's here where things started going off the rails for McClellan's grand strategy. The way he had structured his army meant that all of its most aggressive leaders were concentrated in the Right Wing, and they almost immediately completely disregarded his commands. Believing McClellan's troop estimates to be wildly unrealistic, the trio resolved to hit the rebels as quickly and as hard as they could, eager not to replicate the mistakes of the previous campaigns, and when faced with such complete unanimity from his officers (and their admittedly convincing arguments) Burnside acquiesced to their urging and ordered a forced march the next day, making for Frederick as fast as feasible ...
The Opening Stages
General McClellan's first indication that things were going awry was a series of communique's sent between him and Burnside late into September 11th. Despite the alleged purpose of the "Wings" being to grant his subordinates greater autonomy and flexibility in the face of the unexpected, an adaptation adopted in an effort to prevent the paralysis in command that had previously afflicted the Union's battles against Lee, the general made sure to maintain constant contact and updates with his subordinates, verging on the excessive. And through these, it soon became clear that the Army of the Potomac's Right Wing was moving considerably faster than its peers, alarmingly so.
Indeed, Burnside had been convinced by his three own subordinates that giving the wily southern general breathing room was a recipe for disaster, and so had embarked his men on a breakneck forced march screened by uncharacteristically aggressive use of northern cavalry with the explicit intention of reaching Frederick as quickly as possible, which was essentially the complete opposite of what McClellan had ordered. Needless to say, he wasn't thrilled, and his mood further soured when Burnside dug in his heels and insisted on continuing his course of action through a series of delightfully passive-aggressive letters. George was quite taken aback by the entire debacle, as he'd specifically selected Burnside as a stolid and unremarkable commander who'd ride herd on his unreliable subordinates. Outright sacking Ambrose was considered, but ultimately McClellan decided against it - the stakes were far too high for the battle, and ordering the dismissal of one of his highest commanders on the first day would be an incredibly poisonous way to begin such an important campaign.
With that possibility dismissed, McClellan was still left in the dangerous situation of having his army out of position and uncoordinated, a situation ripe for Lee to take advantage, or so the general believed. Seemingly unable to bring the Right Wing back into position, McClellan began to vacillate on what to do, switching between either committing to the aggressive push and moving forward the rest of his army or impotently insisting that the Right Wing slow down and be more cautious. Burnside would not be dissuaded, however, and the continued rapid advance saw his force make first contact with the rebels on September 12th past noon.
On the Confederate side, Lee had been informed of McClellan's plan by spies within the Union ranks and was thus aware of the danger his overextended army found itself in. He'd split it up in an effort to secure as much of Maryland as possible, gambling on the Federals response being slow enough he'd be able to crush local resistance and reconsolidate in time to meet them in battle. With McClellan moving forward, however, his plan was at risk, and Lee deployed his screens to buy as much time as possible to finish off his attacks and regroup the army. Sent out to secure the rebel left flank, Wade Hampton led a force of cavalry to hold Frederick and maintain a line of defense on the Monocacy River. While not having nearly enough men to put up a realistic defense against a committed infantry attack, this kind of bluff had proven successful before at unnerving cautious Yankee commanders who found it difficult to tell how much of the southron force was smoke and mirrors.
As luck would have it, however, Hampton's foe wasn't a typical cautious Union commander, but the newly brevetted Major General Sebastian Yates, whose force had been granted the vanguard due to its unusually large cavalry component. Yates had grown frustrated with his superiors' hesitation and gullibility during the previous Virginia campaign, and found success in his risky but aggressive tactics at the battle of Chantilly, so when faced with a rebel force of unclear size guarding a river crossing, he wasted no time in ordering an immediate attack as soon as an infantry Divison had formed up. The rebel cavalry put up a brave resistance, but outnumbered significantly, it didn't take long before they were forced back, first to Frederick, and then to the nearby Mt. Catoctin when Union horse pushed right on their heels. Even then, whilst technically in possession of his ordered strategic objective and receiving reports of enemy forces in practically every direction, Yates smelled blood and ordered yet another attack by his increasingly exhausted men, who nonetheless formed themselves up and once again pushed Hampton's cavalry back, securing the Union a fine strategic position for the next day's fighting.
The sheer pace of the advance caught both McClellan and Burnside flatfooted, with the attack on Catoctin Mountain in particular nearly pushing Burnside to the brink, given the state of the men and possible reports of rebel troops on both flanks. But Yates' gambles paid off, and the massive progress combined with the revelation of local rebel weakness seemed to validate the theory that they'd discovered Lee's vulnerable flank. While McClellan sent orders for the Right Wing to consolidate their position and prepare for a more gradual advance, the trio once again urged Burnside to continue their momentum and seize strategic geographic positions before the Confederates had time to rush reinforcements into position. Most likely encouraged by their previous success, Burnside once again agreed to head the uncharacteristically aggressive advance, forgoing a cavalry screen in favor of covering as much ground as possible in the opening they had.
A breakneck march through the valley was little impeded by a stalling action on Hampton's behalf, the Union soldiers soon came up against South Mountain, which unlike Catoctin the Confederates were dug in and prepared to battle for. It provided a crucial natural barrier that protected the vulnerable and spread out Southern army, and taking it quickly was of extreme value to the Union if they wished to punish Lee in his moment of overextension - something both sides knew well. Believing that the more time they were given the harder they'd be to root out, Yates ordered an immediate assault, but as it began, generals Burnside and Hooker arrived.
Given that the primary source we have on the meeting is Hooker's own recollections, they should be taken with a grain of salt, as the antipathy he held towards Burnside was considerable even after the end of the war.* According to Hooker, the commander of the Right Wing has gotten "cold feet" and wanted to call off the assault even as it started, but at his own recommendation, Burnside was persuaded not to undermine the crucial attack out of paranoia at the admittedly confused situation. It should be noted that the Fog of War was extremely dense due to the sheer speed of the advance, with Yates in particular later admitting to having been acting largely out of gut instinct and informed assumption about the enemy rather than any real intelligence on the rebel army. While something perhaps considered normal or admirable today, this was extremely undoctrinal for the Union Army at the time, and given the context, it's reasonable for Burnside to have been nervous about the sheer possibility for disaster they had opened themselves to, especially given the repeated setbacks of the previous campaigns.
(OTL, the only reason Burnside accepted command of the AotP was because Lincoln told him Hooker was next in line. The mutual rancor would obviously make a historian consider Hooker's account somewhat biased, even though this particular interaction was truthfully told)
In any case, the argument was made that calling off the attack just as it began would crush the army's morale and put them in even more danger, so the only rational course of action was to follow through on the original plan, and with that Burnside gave his consent to the deployment of Yates' reserve to push an opening on the left flank. With this, the desperate rebel defense at South Mountain was broken just hours before reinforcements sent by McLaws could arrive, setting the stage for the most climactic battle of the war, and utter disaster for the Army of Virginia.
Impact
It's difficult to overstate how important these first two days of the Antietam campaign were to its ultimate conclusion. The breakneck and - up to that point - utterly uncharacteristic Union advance caught Lee in a moment of extreme vulnerability, and if the rebels had been given just a bit more breathing room, it's quite possible they might've been able to maneuver into a less horribly exposed posture, from which a less total defeat might've been able to be extracted. The withdrawal of the southern army was a closely contested thing, and a better initial position could've allowed them to escape largely intact and/or inflict more disproportionate casualties on the Yankees in what was already an
incredibly bloody battle.
Thus, while the public's focus inevitably tends toward the dramatic conclusion of the battle, Generals Burnside, Kearny, Hooker, and above all Yates deserve a tremendous amount of credit for their insight and bravery that allowed for such crucial initial success and intel from which a greater overall victory could be attained. Operating on gut instinct in a total absence of actionable intelligence is an
extremely difficult thing to accomplish in a military environment, and it's especially impressive given they were bouncing straight back from the defeat at Second Manassas.
Additionally, the fact that they did this in the face of the more or less explicit opposition of General McClellan undoubtedly had a significant impact on their later actions. It undermined their faith in the general's competence, and perhaps furthered the impression insubordination could be excused should it result in a significant enough victory, as George made to effort to punish his unruly subordinates. While this would set an unfortunate precedent for the American military in the future, it undoubtedly played a major role in the spectacular victory the battle ended in, and McCellan's fall from grace.
As the Army of the Potomac convened to reevaluate their battle plan given new information on the Confederate posture and their recent gains, it was with newfound confidence in their own capability and the possibility that a tremendous victory could be won, should the moment be seized ...
