Antietam – Where Habitual Bad Intelligence Defeated an Intelligence Windfall

By Jay Holmes

Last week we looked at the habitual bad intelligence that paved the road to the Battle of Antietam in the American Civil War in Paved with Bad Intelligence–The Road to Antietam. This week, we see how it was enough to negate an intelligence windfall.


Pry Farm at Antietam McClellan's Headquarters image by US Army, public domain

Pry Farm at Antietam
McClellan’s Headquarters
image by US Army, public domain


Lee knew that McClellan was highly intelligent and skilled, but that he was also cautious by nature. Lee was also still hoping to inspire an uprising against the Union in Maryland, and he operated with the assumption that he could defeat McClellan by maneuvering more quickly than the Union Army. Then, for uncertain reasons, Lee violated a major rule of warfare. He divided his forces in the face of a superior enemy and sent Stonewall Jackson’s troops to capture weapons and supplies at Harper’s Ferry.


On the morning of September 13, Union troops of the 27th Indiana Infantry rested in a meadow outside of Frederick, Maryland. They serendipitously took their break at a site that had previously been the location of the General Lee’s headquarters.


At that site, Sergeant John Bloss and Corporal Barton Mitchell found a piece of paper wrapped around three cigars. Known as Lee’s “Lost Orders,” the paper was a message containing Lee’s detailed plan of battle, addressed to Confederate General D.H. Hill. The men quickly handed it over to their commander. The Indiana Division’s adjutant general, Samuel Pittman, recognized the handwriting in the message as belonging to his prewar friend Robert Chilton, now the adjutant general to Robert E. Lee.


Lee's "Lost Orders," Order 191 image by Wilson44691, wikimedia commons

Lee’s “Lost Orders,” Order 191
image by Wilson44691, wikimedia commons


Pittman delivered the message straightaway to General McClellan. McClellan boasted that, with the information he now had, he would gladly be willing to go home if he could not defeat Lee. This “boast” was in fact a hedged bet. If, with the intelligence windfall he had in hand, he could not produce a resounding victory, he should have gone somewhere less pleasant than “home.”


The new information wiped out Pinkerton’s terrible intelligence assessment. McClellan now knew that Lee’s army was dangerously divided into five sections and stretched out over a 35-mile area that was split by the Potomac River. McClellan was twelve miles from the nearest Confederate unit at South Mountain. He was in a position that all commanders dream of in their wildest drunken moments. In their sober moments, they never dare to hope for such generosity from the capricious gods of war.


Alan Pinkertan, Abraham Lincoln, and General McClellan image Library of Congress, public domain

Alan Pinkertan, Abraham Lincoln, and General McClellan
image Library of Congress, public domain


McClellan, poised to become the great Napoleon-like general that he always knew he could be, did what Napoleon never would have done. He waited. Then he waited some more. His division commanders grew restless. Then they grew anguished. Elation fermented into quiet disgust. Finally, after eighteen hours, McClellan gave the order to move.


By now, much of Lee’s army was concentrated in favorable high ground near Antietam Creek. Lee had used the time granted him to send forces to plug the pass at South Mountain. His troops had set up defensive positions there and slowed McClellan’s advance.


Antietam Battle Map image by Hlj, public domain, wikimedia commons

Antietam Battle Map
image by Hlj, public domain, wikimedia commons


The Union Army finally approached Lee’s Confederate Army on September 16. Stonewall Jackson’s troops had still not returned from Harper’s Ferry to Lee’s position, and Lee had less than 40,000 men, their backs to the Potomac.


McClellan’s 75,000 well-rested troops could have conducted a successful flanking maneuver against the Confederates. If McClellan had fallen off his horse or gotten drunk, they likely would have. Instead, McClellan allowed his uncertainty about the intelligence to confuse a clear and reasonable battle plan. McClellan delayed the attack until the following morning.


On the morning of September 17, Union Army General Joseph Hooker led the assault against the now well-entrenched Confederate forces. Rather than concentrating a reasonable portion of his forces against a single point of the Confederate line, McClellan allowed the battle plan to devolve into consecutive piecemeal attacks.


Confederate General Jackson and his troops finally arrived in time for Jackson to earn the nickname “Stonewall” for his defense of the Confederate flank. By the end of the day, both armies had suffered terrible casualties. The dead, wounded, or missing numbered 12,000 on the Union side and 10,000 on the Confederate side.


The balance of losses left McClellan with an even greater numerical advantage, in that a larger percentage of his army was still capable of battle. Over 25,000 of his army were fresh troops that had not yet been engaged.


McClellan's undeployed Union troops near Pry Farm House image by Alexander Gardner, public domain

McClellan’s undeployed Union troops near Pry Farm House
image by Alexander Gardner, public domain


Lee, on the other hand, had no fresh troops remaining. The Confederate lines had held, but they were overall in worse condition than the Union troops. McClellan could still have captured or killed Lee and his army.


With victory staring him in the face, rather than pressing his advantage, McClellan agreed to a truce for both sides to recover their wounded and bury their dead. When night fell, Lee thanked God and withdrew from the field as quickly and quietly as he and his army could. He salvaged enough of his forces to return to defend Virginia, preventing McClellan from having a straight shot through to Richmond. George McClellan had squandered a golden opportunity to deal a crippling blow to the Confederacy.


Union Army burial crew at Antietam image US Army, public domain

Union Army burial crew at Antietam
image US Army, public domain


Lincoln was disappointed in McClellan’s performance, but, unlike McClellan, he knew how to seize an opportunity. The victory at Antietam Creek gave him public relations momentum. On September 22, Lincoln announced his Emancipation Proclamation.


The Proclamation would not take effect until January 1, 1863, and then, it was conditional. Only slaves in Confederate territory were freed. Slaves in the four Union slave states still remained in bondage. Since the Confederate States were not inclined to obey any Union proclamations, only around 40,000 slaves in captured territory were actually freed at the time of the Proclamation. However, the real impact of the bloodiest day in US history was that Lincoln was able to score a monumental diplomatic victory. After the victory at Antietam and the Emancipation Proclamation, no European nation was willing to support the Confederacy in a war to defend the institution of slavery.


Bloody Lane at Antietam filled with Confederate dead image by Alexander Gardner, US Army, public domain

Bloody Lane at Antietam filled with Confederate dead
image by Alexander Gardner, US Army, public domain


Due to poor intelligence and the mishandling of intelligence, Lee miscalculated the sentiments of Maryland, and McClellan dawdled away a windfall opportunity. Lee allowed himself to anticipate a States’ Rights event in Maryland, and the false analysis that men would throw themselves in for the Confederates. His failed intelligence caused him to launch a campaign that he had little chance of winning. McClellan’s refusal to accept and act on the best intelligence kept him from completely crushing Lee’s army and marching on Richmond. Nearly three more years of bloody war remained to be fought, but the fate of the Confederacy was sealed. It was a case when a perfect intelligence windfall was defeated by habitual misuse of intelligence.


Antietam National Cemetary image by Acroterion, wikimedia commons

Antietam National Cemetary
image by Acroterion, wikimedia commons

Paved with Bad Intelligence–The Road to Antietam

By Jay Holmes

September 17, 1862, is remembered by US military history students as the bloodiest day in US history. It should also be remembered as a critical lesson to all members of the US intelligence community and the US military. Even a perfect intelligence windfall can be defeated by habitual bad intelligence.


Antietam National Cemetary image by Acroterion, wikimedia commons

Antietam National Cemetary
image by Acroterion, wikimedia commons


On December 20, 1860, the South Carolina state government voted to secede from the Union, beginning the American Civil War with a bloodless political act.

Many Southern politicians guessed that their states, too, could happily secede and slip away from the Union without suffering much loss. Wealthy Southern plantation owners thought that by seceding, they could continue to use slavery as their primary economic tool. Most Southerners did not own slaves or plantations, so the secession concept was marketed to them under the banner of “States’ Rights.” By May 1861, eleven Southern states had voted to secede and had formed the Confederate States of America.

President Lincoln, like a majority of Northerners, was opposed to slavery, but he thought that he was not in a position to declare an end to the practice. Slavery was still legal in the Union border states of Missouri, Kentucky, Maryland, and Delaware, and Lincoln did not want those four states to secede and join the Confederacy.

On May 24, 1862, the US government signaled its determination to reverse the secession of the Southern states by sending an army across the Potomac River.

With the capture of Alexandria, Virginia, the US Army improved the security of nearby Washington D.C. and established a valuable base for operations against the Confederacy.

For the Confederacy, it was critical to prevent a Union capture of its capital, Richmond, Virginia, and the surrounding area, including the agriculturally rich Shenandoah Valley. In July, when the Union army moved south from Alexandria, the Confederacy concentrated all the forces it could muster for a counterattack.

On July 21, 1861, at Manassas Junction, the Confederates soundly defeated an overconfident and poorly organized Union Army and sent it into retreat to Alexandria. The battle is commonly referred to as the Battle of Bull Run.


Manassas National Battlefield Park image by ARSNL, public domain

Manassas National Battlefield Park
image by ARSNL, public domain


The Union defeat at Manassas shocked the overconfident Northerners. For the general public in the South, the victory proved the superiority of Southern military abilities and indicated certain victory and independence for the Confederate States.

The Confederacy was hoping for foreign assistance from cotton-consuming countries such as France and England and from neighboring Mexico. The victory at Manassas helped their diplomatic efforts.

While the general public in the South loudly celebrated the victory at Manassas, most of the South’s senior military leaders were not quite so willing to underestimate the North’s military abilities or political determination to retake the Confederacy. With each passing month, more Confederate leaders realized that time was not on their side, and that the Union would eventually organize itself sufficiently to use its vastly superior resources in manpower and industry to win the war.

The Confederate leadership thought that their best strategy was to keep the Union busy on as many fronts as possible in order to ward off a major Union invasion of the South. They reasoned that, if the Confederacy lasted long enough, it would eventually receive enough foreign assistance to ensure its long-term independence. The single greatest diplomatic obstacle for the South in receiving foreign assistance was that they were seeking recognition and aid from nations that had already outlawed slavery. Those nations took a dim view of slavery in the Confederacy.


General Robert E. Lee public domain, Library of Congress

General Robert E. Lee
public domain, Library of Congress


By the summer of 1862, the South’s need for foreign aid was becoming more urgent. Confederate General Robert E. Lee thought that defensive victories on Southern ground would never be enough to gain the image of legitimacy that the Confederacy needed to acquire that aid. With the agreement of Confederate President Jefferson Davis and his cabinet, Lee devised a plan to invade Union territory in Maryland and West Virginia. They hoped that Maryland would respond to a Confederate invasion by joining the Confederacy, bringing much-needed conscripts and material wealth.

On September 2, 1862, Lee’s confident Army marched happily into Maryland. They might have been less cheerful if they had known that Lee’s plans were based on an extremely bad intelligence assessment of the conditions in that state. Although most Marylanders did not actively oppose Lee’s Army, they did not lend assistance or join his forces. The “liberation” of Maryland was not going as planned.

President Lincoln recognized Lee’s invasion as a serious problem, but he also recognized a great opportunity. The Union’s Army of the Potomac now had 75,000 well-equipped soldiers. That Army was well trained by its popular commander, General George McClellan. McClellan loved that Army, and they loved him. Morale was high, and the troops were ready and willing to face Lee’s soldiers.


General George McClellan public domain

General George McClellan
public domain, wikimedia commons


While Lee moved his army forward on a foundation of faulty intelligence, the Union forces had their own intelligence issues. In 1862, there was nothing like a “CIA,” or even a fledgling “OSS.” McClellan relied on Alan Pinkerton and his informal intelligence service. Pinkerton efficiently spied for McClelland.

Although Pinkerton’s men were able to gain access to Confederate information, Pinkerton lacked any basic ability to reasonably assess that information. He repeatedly overestimated the size of Lee’s forces. President Lincoln and the Union War Department never believed Pinkerton’s information, but McClellan did, and he operated accordingly. When McClellan maneuvered his army to oppose Lee, he did so under the assumption that he was facing a Confederate army numbering over 100,000 troops, when, in fact, Lee had 54,000. And so it was that two well-trained armies, both equipped with terribly inaccurate intelligence estimates, marched to battle.

Next week, we will look at the Battle of Antietam and how a perfect intelligence windfall was defeated by habitual intelligence mishandling.