Until Edwin C. Fishel’s The Secret War for the Union was published in1996 the history of Civil War military intelligence was mostly a collection of uncorroborated cloak and dagger tall tales featuring daring spies and dangerous missions packaged in flowery Victorian prose. In these spy thrillers, however, the truth rarely survived first contact with the enemy. To understand the true nature of Civil War military intelligence requires an examination of its three most challenging characteristics. First, military intelligence operations (called “secret service” during the war) were often ad hoc affairs carried on without much direction or oversight from higher authorities. The second challenging characteristic centers on the types of intelligence sources available in nineteenth-century warfare. These included spies, army scouts, regular cavalry units, and balloonists. In addition, the use of visual signaling systems and the telegraph both provided intelligence to commanders and offered an opportunity for the enemy to obtain intelligence by intercepting signals and decrypting those that were encrypted. A final very important source of intelligence came from the interrogation of enemy prisoners of war and deserters and from local civilians and refugees. Correctly assessing the accuracy and value of that information—the third and final challenging characteristic of Civil War military intelligence—probably caused the most headaches because the line separating the truth, the half-truth, and everything but the truth was often unclear or non-existent. Enthusiastic but untrained officers and civilians made this process less effective. To successfully overcome or at least neutralize the challenging characteristics described above, both sides—to varying degrees—experimented with ways of systematizing information collection and analysis and professionalizing intelligence personnel in the hopes of increasing the efficiency and effectiveness of intelligence operations. McClellan famously used the Pinkerton Detective Agency to manage his intelligence operations. General William Rosecrans was an organizational wizard when it came to military intelligence operations. Rosecrans systematized the collection, reporting, and analysis of information gleaned from scouts, spies, newspapers, signal intercepts, deserters, prisoners, and civilian refugees. This information trove then went to Rosecrans’ staff who condensed the reports into a daily digest called Summaries of the News. Rosecrans also benefited from the services of Colonel William Truesdail’s Army of the Cumberland Police operating in occupied Nashville, Tennessee. Truesdail’s Army Police oversaw spying, scouting, and counterintelligence missions, conducted criminal investigations, apprehended Union deserters, infiltrated Confederate smuggling rings, and seized contraband. In October 1862, Grant tasked General Grenville M. Dodge with creating an intelligence organization for the upcoming campaign against Vicksburg, Mississippi. By mid-1863, Dodge had over 130 scouts and spies at work in Mississippi, Tennessee, Alabama and Georgia. The most proficient military intelligence organization of the war, however, was the Army of the Potomac’s Bureau of Military Information (BMI). Created by Major General Joseph Hooker after McClellan’s departure in 1862, the BMI became the war’s first all-source intelligence service, which collected information from spies, scouts, cavalry reconnaissance missions, balloon and signal tower observations, captured correspondence, signal intercepts, enemy newspapers, and interrogations of enemy prisoners, deserters, refugees, local civilians, and slaves. In Confederate armies, officials left intelligence matters to individual field commanders. Foremost among them was Robert E. Lee, who functioned as a one-man intelligence staff for the Army of Northern Virginia. He employed scouts and spies for specific missions, though he never completely trusted them, orchestrated counterintelligence operations, initiated covert actions, and even tapped into the Signal and Secret Service Bureau’s Secret Line before the Gettysburg campaign. Many of Lee’s officers emulated his approach. One final characteristic makes the study of military intelligence during the Civil War difficult. The secrecy and discretion required of those who produced or managed military intelligence created a shroud of secrecy, and most operatives scrupulously avoided leaving paper trails, denying the enemy—and historians—the means of unmasking them.
The Life of a Spy - In Nine Tableaux, by Thomas Nast
Harper's Weekly October 24, 1863
Before publishing his groundbreaking monograph, The Secret War for the Union, Edwin C. Fishel bemoaned the lack of scholarly interest in Civil War military intelligence operations. “Intelligence historians don’t give damn about the Civil War,” he complained, “and Civil War historians don’t give a damn about intelligence.”  Nevertheless, he also knew scholars had good reason not to take it seriously. Until his book appeared in 1996, the “true” history of Civil War military intelligence was mostly a collection of uncorroborated cloak and dagger tall tales featuring daring spies and dangerous missions packaged in flowery Victorian prose. In these spy thrillers, however, the truth rarely survived first contact with the enemy. As a result, the dubious nature of what passed for intelligence history seemed unworthy of serious consideration by both intelligence and Civil War historians. Fishel’s work, however, showed that giving a damn could reap significant rewards.
To understand the true nature of Civil War military intelligence requires an examination of its most challenging characteristics, keeping in mind nineteenth-century military theorist Antoine-Henri Jomini’s warning that though “it is unquestionably of the highest importance to gain this information,” actually getting it was “a thing of the utmost difficulty, not to say impossibility.” First, military intelligence operations (called “secret service” during the war) were often ad hoc affairs carried on without much direction or oversight from higher authorities. Most field commanders, however, needed little incentive to gather intelligence for, as Union general Daniel Butterfield so eloquently put it, “We cannot go boggling around until we know what we are going after.” Nevertheless, no official army intelligence manual existed for hundreds of newly minted and woefully inexperienced Civil War officers whose smart new uniforms were often the only soldierly thing about them. A self-taught crash course in the manual of arms and company drill was commonplace, and these and other more pressing needs crowded out serious consideration of the intelligence function. Not even the U.S. Military Academy at West Point spent much time exposing cadets to intelligence collection and analysis, leaving it to the genius of the man on horseback to figure it out on the fly. Though some gained valuable experience during the Mexican War, many Civil War officers—even those with a West Point pedigree—learned the intelligence business on the job, making it up as they went along and relying on wits and guts to get them through.
The second challenging characteristic centers on the types of intelligence sources available in nineteenth-century warfare. As in all wars, espionage was an important method of acquiring information on the enemy. In the Civil War, this consisted of spies employing guile and deception to gather information for transmission to a waiting commander, knowing all too well that a blown cover meant a date with the hangman. Trapped behind enemy lines by the war’s ebb and flow, both Southern Unionists and Confederate sympathizers became prime spy candidates. Operating on their home ground, noted a Union officer, meant these people knew well “its men—its condition—its movements, feelings, habits, and everything else.” Whether motivated by patriotism, the lure of adventure, or the pay (sometimes $500 per mission—or around $13,000 today—for the most proficient spies), men and women, blacks and whites signed on to practice the world’s second oldest profession. These included such figures as Elizabeth Van Lew, Samuel Ruth, Rebecca Wright, Charles S. Bell, Pauline Cushman, Isaac Silver, Ebenezer McGee, James George Brown, and Philip Henson. In addition, numerous African Americans—both free and slave—risked all to help save the Union and destroy slavery, including Harriet Tubman, John Scobell, Mary Richards Bowser, Robert Smalls, Charlie Wright, and countless others.
The secrecy and discretion required by the job, however, makes identifying them and uncovering what they did a substantial challenge. “Much of my experience,” a Confederate scout observed, “was acquired when I was alone with God.” Always fearful of detection, however, even keeping God in the loop could be dangerous, so most operatives scrupulously avoided leaving paper trails, denying the enemy—and historians—the means of unmasking them. Only a handful of secret service personnel published accounts of their service and, unfortunately, these mostly fictionalized accounts dominated the history of the intelligence war and indelibly shaped the public’s overall perception of it. Most notably, the exciting exploits of Rose O’Neal Greenhow, Belle Boyd, Allan Pinkerton, and Lafayette Baker dominated the war’s intelligence narrative and gave the impression that spying was the most important means of gaining intelligence. Upon closer inspection, however, these operatives-turned-authors were far better at stealing the limelight than pinching enemy secrets. Even her biographer called Boyd “the most overrated spy” of the war. Fishel slammed Pinkerton’s memoir for containing “a high proportion of fiction” and dismissed Baker’s account for having “the literary merit and the believability of the dime novel.” Nevertheless, these spellbinding offerings formed what Fishel called the “magnolia blossom school” of Civil War intelligence literature, a collection of uncorroborated tales that captured the public imagination and, in so doing, obscured other important aspects of the intelligence story. “[S]pies who wrote memoirs are invariably more famous,” observed historian Peter Maslowski, “but were often less important than those who did not.”
One figure nudged from the spotlight was the army scout. During the war, commanders on both sides deployed scouts to gather information, usually as individual operatives or in scouting units like, for example, Young’s Scouts (Union) in the Shenandoah Valley and Coleman’s Scouts (Confederate) in Middle Tennessee. Scouts were often volunteers from the ranks or intrepid civilians motivated by patriotism, a sense of duty, and/or the pay. Depending upon their effectiveness and reliability, scouts could earn $60 a month or more, which was a significant improvement over the paltry $13 a month earned by army privates. The thrill of adventure also enticed many eager young men seeking escape from the drudgery of camp life and endless drilling. When his captain asked for volunteers for “extra dangerous duty,” Archibald Rowand did not hesitate. “I looked at Ike Harris and Ike looked at me,” he recalled, “and then we both stepped forward.” But their excitement was soon checked. “They took us to headquarters and gave us two rebel uniforms,” he continued, “and we wished we had not come.” When asked why they volunteered, Rowand replied: “We were boys [and] wanted to know what was the ‘extra dangerous duty.’”
Unlike spies, scouts remained in enemy territory for only a short time and then returned to their base bearing information from, for example, conversations with enemy soldiers or locals, personal observations of enemy activity, or reading captured mail. In addition, scouts acquired enemy newspapers, which became a highly desirable yet easily obtained source of intelligence. Due to lax censorship, war correspondents reported all the news they saw fit to print, regardless of the sensitive military information they might divulge. Even so, commanders had to exercise caution when reading since reporters also embellished and even fabricated stories to sell papers. Nevertheless, newspapers were such a useful source that one Confederate commander ordered his scouts to bring him enemy dailies at least three times a week. Courtesy of his scouts, General Ulysses S. Grant routinely read Richmond newspapers to get the latest on troop movements in the city, the activities of Confederate leadership, and the price of civilian goods, which became a barometer of civilian morale as the Union noose tightened around the Confederacy in 1864-1865. Unable to communicate directly with Major General William Tecumseh Sherman during his March to the Sea in 1864, Grant kept abreast of his subordinate’s romp across Georgia through reports in these same Southern newspapers. Confederate General Robert E. Lee perused Northern newspapers regularly, especially the Philadelphia Inquirer due to the apparent accuracy of its reporting. On one occasion, Lee obtained a copy of the Washington Morning Chronicle that included an official medical report detailing the strength and composition of the Army of the Potomac. In the West, Braxton Bragg often consulted enemy papers and even planted fake stories in the Chattanooga Daily Rebel knowing that Union commanders regularly scanned it for military information.
Although scouts and spies were technically different in how they operated, both faced summary execution if captured plying their trade. “[T]he army scout,” observed one Union operative, “literally takes his life in his own hands [because] he may expect no quarter.” General Orders No. 100 issued by Union authorities in 1863 made clear that spying was “punishable with death by hanging by the neck, whether or not he succeed[ed] in obtaining the information or in conveying it to the enemy.” Scouts captured “within or lurking about the lines of the captor” and who were “disguised” in civilian garb or wearing “the uniform of the army hostile to their own” would also be put to death. Perhaps the most famous execution for espionage occurred in 1863 when Union Brigadier General Grenville Mellen Dodge captured, tried, and executed a Confederate scout named Sam Davis in Pulaski, Tennessee. Before going to the gallows, the young Davis refused to divulge the names of his fellow scouts in exchange for his life. His steadfast loyalty to his cause and comrades has become an iconic moment in Confederate lore and his death transformed the youth into a Southern martyr. However, Davis was only one of many secret service operatives on both sides summarily executed for spying during the war, though the actual number remains unknown. Women scouts and spies, however, seemed to be the only exception to this condign punishment, as evidenced by the fact that high profile spies like Rose Greenhow and Belle Boyd were exiled, not executed. In a notable exception, however, Confederate authorities in Tennessee appeared ready to hang Union spy Pauline Cushman before Federal forces rescued her in 1863.
Information also came from regular cavalry units whose mobility and speed could find enemy formations, determine the location of flanks, detect and track troop movements, examine roads and terrain, and then speedily relay this information to headquarters. For both sides, cavalry reconnaissance missions, especially when in close proximity to the enemy, became a wellspring of combat intelligence throughout the war. “Had [field commanders] been asked to name their most important intelligence source,” Fishel asserted, “the cavalry would have been their choice.” Regular mounted units also performed a key counterintelligence mission by screening the movements of their own army from the enemy’s prying eyes. Early in the war, Confederate cavalrymen like Major General J. E. B. Stuart literally rode circles around the Federals when it came to reconnaissance and intelligence collection but, by war’s end, Union cavalry proved more than a match for their Southern counterparts on that score.
A more novel reconnaissance method required hydrogen gas instead of hay. The potential of aerial reconnaissance by balloon attracted the attention of aeronauts, as they were then called, on both sides, but the Union was the first to operationalize it. Shortly after the war started, balloon enthusiast Thaddeus Sobieski Constantine Lowe climbed aboard the Enterprise and made several tethered ascents over the National Mall hoping to impress President Abraham Lincoln with the potential of military ballooning. On one flight, Lowe used a portable telegraph connected by wire to the White House to inform the president that he could see for miles in all directions. Impressed, Lincoln approved the creation of a balloon corps and Lowe took his contraptions to the battlefront in Virginia and made numerous ascents—sometimes under enemy fire—during the Peninsula, Chancellorsville and Gettysburg campaigns. Although Lowe’s balloons netted important information and on occasion helped direct artillery fire, bureaucratic infighting, accusations of financial mismanagement, and fading army interest killed the experiment by the end of 1863. Federal forces on the Mississippi River floated a balloon in March 1862 to locate Confederate gunboats off Island No. 10, but aside from this instance, Union aerial reconnaissance in the West never got off the ground. Though resource-poor, Southerners managed to float the so-called Silk Dress Balloon constructed from multi-colored strips of silk cloth not, as legend has it, from silk dresses donated by the women of Savannah and Charleston. Like Lowe’s balloon, the more colorful Southern version flew missions during the Peninsula campaign but its capture by Union forces in July 1862 grounded the Confederate aeronauts for good.
Military intelligence also came from the interception of enemy communications. Built from the ground up or perched atop buildings, signal towers provided a platform to observe distant enemy movements but also to transmit messages by flags and torches using a visual signaling system created by Major Albert James Myer, head of the Union Army’s Signal Corps. In the South, Captain Edward Porter Alexander, who was Myer’s assistant before the war, adapted his former superior’s handiwork for use in the Confederate armies. Visual signaling became an important means of communication but one easily compromised since a man waving flags or torches atop an exposed signal tower could be seen by friend and foe alike. This led both sides to devise ciphers to prevent messages from being intercepted and read, though these improvised codes were far from foolproof.
Invented in 1844, Samuel Finley Breese Morse’s telegraph revolutionized civilian communications, but the Civil War would be its first test in wartime. Using the Beardslee Telegraph Machine, the first portable telegraph adapted for use in the battle zone, commanders could hold real time councils of war with distant subordinates, transmit timely reports on battles and campaigns, request reinforcements, move troops within and between areas of operation, or call for needed ammunition during a fight. Civilian leadership also counted on the telegraph to remain informed and to coordinate strategy. At all hours, Abraham Lincoln could be found in the War Department telegraph office waiting for news from distant battlefields.
To maximize the benefits of this new technology, the Union created the U.S. Military Telegraph headed by Anson Stager while Major William Norris oversaw telegraphic communications in the Confederate Signal Corps, though lack of resources and loss of lines to Union forces severely handicapped Southern efforts. Like visual signals, telegraph messages could be intercepted by tapping the lines, forcing both sides to develop cipher systems to protect them. The Confederates employed the Vigenère system, which Union cipher operators cracked, while the Union preferred the Route Transposition Cipher, which apparently defied Southern code-breaking efforts. So important was the need to secure messages from prying ears that Grant employed a full-time cipher clerk and never went anywhere without him.
The last source of intelligence was the least exciting yet one of the most important producers of combat intelligence. Interrogations of prisoners of war and enemy deserters became an important tool for obtaining order of battle intelligence, or information on the enemy army’s basic organization and composition, including the identity of specific corps, divisions, brigades, and regiments and their respective commanders. Knowing the foe’s order of battle, for example, could help determine the disposition, composition, strength, and combat efficiency of his forces. In the hands of a skillful interrogator, enemy prisoners and deserters could unwittingly divulge critical information simply by answering mundane questions about their companies, regiments, or brigades. “Interrogation,” Fishel concluded, “produced a volume of reports exceeding that of all other sources put together.” Eventually, Union intelligence officers in the Army of the Potomac became so proficient at extracting order of battle information that Gen. Robert E. Lee ordered any Confederate soldier captured by the Federals to “preserve entire silence with regard to everything connected with the army” and maintain “that secrecy so essential to success.”
Close questioning of refugees and local civilians also produced useful information on terrain, the location of roads and towns, and the whereabouts of hostile forces, especially during incursions into enemy territory where maps were non-existent. As Union armies penetrated deeper into the South, especially after the Emancipation Proclamation became Federal policy in 1863, commanders found local slaves and “contrabands” (escaped slaves) to be quite knowledgeable—and very willing—informants. Black slaves “repeatedly threaded their way through the lines of the rebels exposing themselves to bullets,” wrote famed abolitionist Frederick Douglass, “to convey important information to the loyal army of the Potomac.” A Union officer serving in St. Louis in 1861 proclaimed that the “German was always ready with his musket and the colored man with his information.” This was not lost on Robert E. Lee. “The chief source of information to the enemy,” he complained in May 1863, “is through our Negroes.”
Collecting information, however, was but the opening salvo in the intelligence war. Correctly assessing the accuracy and value of that information—the third and final challenging characteristic of Civil War military intelligence—probably caused the most headaches because the line separating the truth, the half-truth, and everything but the truth was often unclear or non-existent. Also complicating intelligence evaluation, to borrow a phrase from former Secretary of Defense Donald Rumsfeld, was the nagging persistence of the unknown unknowns— the things we don’t know we don’t know—that sowed uncertainty, encouraged indecisiveness, and compromised intelligence assessments. Jomini advised commanders to “neglect no means of gaining information of the enemy's movements,” but also warned that “Perfect reliance should be placed on none of these means.” More to the point, military theorist Carl von Clausewitz stated that many intelligence reports were “contradictory; even more are false, and most are uncertain.” Moreover, though a lack of information could cause problems, the opposite was also true. With dozens of reports flooding in, Clausewitz observed, “We know more but this makes us more, not less uncertain.” A Union officer serving in Virginia encountered this brutal truth first-hand when he found that his informants had placed a certain Confederate division "in our front--on our left & rear & on its way to P[ennsylvania]." Add to this scenario whizzing minié balls, exploding shells, impenetrable smoke, and the cries of the wounded and the average combat officer would be sorely tempted to take counsel of his fears rather than of his intelligence.
The problems associated with employing enthusiastic but untrained civilians in secret service also complicated intelligence assessment, especially when it came to judging the veracity of the information they collected and ensuring they maintained maximum secrecy on the job. Many civilian operatives were ignorant of military organization, which became especially troublesome if they could not, for example, distinguish between a company and a division marching along a road or determine the identity of enemy units from their flags or insignia. Lack of appreciation for secrecy and discretion, moreover, could also prove disastrous. One Confederate spy attracted suspicion while riding a train through Union-occupied Middle Tennessee because, as one witness testified, whenever the train stopped at a station “out of the window would go her head” to ask those on the platform about the number and location of Union troops in the area. Not surprisingly, this reckless display led to her arrest, but her indiscretion proved more damaging when she divulged to Union officials that she belonged to a smuggling ring and carried secret correspondence for Confederate General Braxton Bragg.
In the East, Federal authorities determined that Belle Boyd and Rose Greenhow were both Confederate spies because they did little to hide their supposedly secret service. Their brazenness got them both arrested and exiled in 1862, thereby ending two promising espionage careers that could have benefitted the Confederacy later in the war.
Lastly, commanders often paid operatives based upon the value of the information they delivered. To the more ethically challenged scout or spy, this meant the tallest tale could net the biggest paycheck, further complicating the task of separating fact from fiction. “As a general thing,” wrote one observer, “scouts are perfectly worthless. They are usually plausible fellows who go out [just past] the picket line and lie on the ground all night under a tree and come back to headquarters in the morning and lie there, giving wonderful reports about the enemy, fearing no contradiction.” As with the citizen-soldiers in the ranks, the armies could only hope that these civilians-turned-scouts would become seasoned veterans in a hurry.
To successfully overcome or at least neutralize the challenging characteristics described above, both sides—to varying degrees—experimented with ways of systematizing information collection and analysis and professionalizing intelligence personnel in the hopes of increasing the efficiency and effectiveness of intelligence operations. When Union Major General George Brinton McClellan took command of the Union army after the disaster at First Bull Run in late 1861, he outsourced intelligence collection to a civilian contractor named Allan Pinkerton, head of a private detective agency and a major figure in the capture of Rose Greenhow in Washington. During the Peninsula Campaign in 1862, one of Pinkerton’s main tasks was determining the size of Confederate forces defending Richmond. To do this, he relied primarily on interrogations of refugees and Confederate prisoners and deserters. He managed to identify all 178 Confederate regiments protecting Richmond but both he and McClellan feared many more regiments remained undetected, which led Pinkerton to routinely double Confederate strength estimates as a precaution. However, even these inflated numbers failed to satisfy his boss, who upped the figures even more. As historian James McPherson noted: “McClellan believed what he wanted to believe—that the enemy outnumbered him and he therefore could not undertake an offensive until he outnumbered the enemy—something that, given McClellan’s psychology, was never likely to happen.” McClellan’s subsequent defeat in the Seven Days battles at the hands of Robert E. Lee showed that even an effective intelligence service might not be enough to overcome the fears and fixations of the man at the top.
McClellan’s instinctive risk-avoidance was once again on display during the Antietam campaign after he obtained—by pure happenstance—a copy of Lee’s Special Orders No. 191, a document outlining the Confederate commander’s basic strategy and revealing the dispersed nature of his army in Maryland. Despite bragging that “I have the plans of the Rebels, and will catch them in their own trap,” the Young Napoleon remained true to form. Reacting slowly and cautiously to the Lost Order, as it was called, in part due to his erroneous belief that Lee still outnumbered him by 40,000 men, McClellan’s delay gave his opponent precious time to escape the trap and fight Union forces to a bloody draw along Antietam Creek. As the saying goes, intelligence does not make decisions in war, only commanders do.
Another Union officer, Major General. William Starke Rosecrans was an organizational wizard when it came to military intelligence operations. To him, wrote historian Steven Woodworth, “War was not an art . . . but a science” to be waged “scientifically and methodically, preparing for every contingency and removing all uncertainty.” To Rosecrans, this meant collecting as much information as possible to lift the fog of doubt and reveal the correct course of action. In early 1863, as his Army of the Cumberland faced General Braxton Bragg’s Confederates in Middle Tennessee, Rosecrans systematized the collection, reporting, and analysis of information gleaned from scouts, spies, newspapers, signal intercepts, deserters, prisoners, and civilian refugees. This information trove then went to Rosecrans’ staff who condensed the reports into a daily digest called Summaries of the News. Given the rugged terrain in Middle Tennessee, topographical intelligence was also a high priority. Lacking adequate maps of the area, Rosecrans filled the void with a system of information maps, which were detailed topographical sketches that, like the Summaries, were regularly updated and disseminated to subordinates in the field.
Rosecrans also benefited from the services of Colonel William Truesdail’s Army of the Cumberland Police operating in occupied Nashville, Tennessee. Truesdail’s Army Police oversaw spying, scouting, and counterintelligence missions, conducted criminal investigations, apprehended Union deserters, infiltrated Confederate smuggling rings, and seized contraband. Truesdail’s men also monitored the mail for enemy correspondence but also to prevent obscene prints and books from reaching Union soldiers. The Army Police spent much time combating the so-called Petticoat System, a group of Nashville women who smuggled medicine, correspondence, and other contraband to Confederate forces hidden in their voluminous dresses. This problem became so bad that Truesdail, in an attempt to make an example of two of these women, sent them to enjoy, as he wrote, the “widely dispensed hospitalities” of a prison camp in Ohio. Truesdail also sought information on Bragg’s army through his so-called spy department which employed over 100 scouts and spies. With all these intelligence assets at his disposal, Rosecrans was arguably one of the best-informed commander of the war. This careful intelligence preparation, moreover, became the foundation of Rosecrans’ carefully orchestrated and cleverly deceptive maneuver campaign that drove Bragg out of Middle Tennessee in the spring of 1863.
Though Union general Ulysses S. Grant pursued intelligence during his early commands, it was not until the disastrous surprise attack at Shiloh in April 1862 that he began to take intelligence seriously. In October 1862, Grant tasked General Grenville M. Dodge with creating an intelligence organization for the upcoming campaign against Vicksburg, Mississippi. By mid-1863, Dodge had over 130 scouts and spies at work in Mississippi, Tennessee, Alabama and Georgia. When Vicksburg fell in July, Dodge’s men had completed over 200 missions, logged thousands of miles, and submitted hundreds of reports on Confederate forces in Vicksburg and in the region. One of his most prolific scouts, Charles S. Bell, carried out thirty-seven missions by himself, sometimes disguised as a Confederate staff officer. On two occasions, Bell delivered critical intelligence to Grant as he maneuvered toward Jackson and then Vicksburg. With the aid of Dodge’s intelligence service, Grant bagged an entire Confederate army, captured the last Confederate bastion on the Mississippi River, and sliced the Confederacy in half at Vicksburg.
The most proficient military intelligence organization of the war, however, was the Army of the Potomac’s Bureau of Military Information (BMI). Created by Major General Joseph Hooker after McClellan’s departure in 1862, the BMI became the war’s first all-source intelligence service, which collected information from spies, scouts, cavalry reconnaissance missions, balloon and signal tower observations, captured correspondence, signal intercepts, enemy newspapers, and interrogations of enemy prisoners, deserters, refugees, local civilians, and slaves. The head of the BMI, Colonel George Henry Sharpe, and his staff systematically collated, analyzed, and attempted to corroborate this mass of information before boiling it down into an intelligence brief for the commander of the Army of the Potomac. Though he deployed numerous scouts and spies, the interrogation of enemy prisoners and deserters for order of battle intelligence was one of the BMI’s most important functions. By collating, comparing, and corroborating information gleaned from hundreds of interrogations, Sharpe could effectively monitor the location, composition, and movements of Lee’s army in Virginia.
The value of the BMI’s expertise with order of battle intelligence became evident during the Gettysburg campaign in 1863. Early in the campaign, Sharpe learned from prisoners that Lee’s army was headed for Pennsylvania, a startling revelation that spurred the Union pursuit. After the mauling Lee’s army suffered on the second day at Gettysburg, prisoner interrogations and Sharpe’s knowledge of the Army of Northern Virginia’s organization led to the discovery that Major General George Edward Pickett’s division was the only fresh division Lee had left. This intelligence influenced Union Major General George Gordon Meade’s decision to stay and fight on the third day rather than retreat. The defeat of Pickett’s Charge the following day revealed the wisdom of that decision and underscored the value of order of battle intelligence.
In July 1864, after Ulysses S. Grant had slugged it out with Lee from the Wilderness and Spotsylvania to the outskirts of Richmond and Petersburg, the BMI discovered that a corps under Lieutenant General Jubal Anderson Early had departed Lee’s army outside the Confederate capital and slipped across the Potomac to raid Washington, D.C. This timely revelation, however, came not from testimony of captured Confederates, but from the unusual absence of prisoners and deserters coming from Early’s division. From this lack of evidence, Sharpe concluded that Early’s command was no longer with Lee’s army outside Richmond and, combined with reports coming from BMI agents in the Shenandoah Valley, was headed toward the Potomac River. Alarmed, Grant rushed reinforcements to the Federal capital and successfully blunted Early’s attack. With successes like these, Sharpe could brag—with justifiable confidence—that his outfit knew “each regiment, brigade, and division” in Lee’s army down to “their officers and locations.” Grant seconded this assessment, telling the War Department: “Deserters come in every day enabling us to keep track of every change the enemy makes.”
During the siege of Richmond and Petersburg in 1864, Sharpe posted BMI scouts along the major railroads between the capital and other parts of the Confederacy to watch for troop transfers. He also expanded the BMI’s reach by coordinating activities and intelligence sharing with other Federal armies operating in Virginia, North Carolina, and the Western Theater. To get information from inside Richmond, Sharpe ordered his chief of scouts, Judson Knight, to open communications with the Richmond Union Underground headed by Elizabeth Van Lew. Her covert organization of Southern Unionists gathered military and political intelligence from the Confederate capital and Van Lew sent their findings through the lines in secret messages encoded with a homemade cipher. One of her operatives, Samuel Ruth, was superintendent of a major rail line in Richmond and provided the Federals with valuable information on railroad timetables, cargoes, and troop transports. After the war, Sharpe testified that "the regular information obtained by our Bureau from the City of Richmond . . . we owed to the intelligence and devotion of Miss E. L. Van Lew." Unlike Greenhow and Boyd, however, neither Van Lew nor her fellow Unionists wrote postwar memoirs for fear that their defeated and embittered Confederate neighbors would exact revenge if they found out.
The fires that burned after Lee’s army evacuated Richmond in April 1865 destroyed many government and army records, leaving only fragments and dim outlines for historians to use in reconstructing and assessing Confederate military intelligence operations. Although bedeviled by many unknown unknowns caused by the conflagration, historians do know that in 1862 the Confederate War Department created the Signal and Secret Service Bureau, a shadowy organization headed by Major William Norris that dabbled in military intelligence operations. Norris had some agents in the field, including J. Franklin Stringfellow, who once delivered news to J.E.B. Stuart that led to a raid on Union Major General John Pope’s headquarters prior to the Battle of Second Bull Run. But the Secret Service Bureau did not organize, systematize, or oversee military intelligence operations for the field armies nor did it coordinate activities or promote information sharing between theaters. Norris’ bureau focused primarily on covert operations and running a clandestine communication network called the Secret Line between Richmond and Confederate agents posted in Washington and Canada.
With regard to the armies, Confederate officials left intelligence matters to individual field commanders. Some officers, however, expended minimal effort on organizing and systematizing intelligence operations and instead trusted their own intuition and improvisational skills when the situation demanded it. Foremost among them was Robert E. Lee, who functioned as a one-man intelligence staff for the Army of Northern Virginia. He employed scouts and spies for specific missions, though he never completely trusted them, orchestrated counterintelligence operations, initiated covert actions, and even tapped into the Signal and Secret Service Bureau’s Secret Line before the Gettysburg campaign. Unlike his Federal counterparts, Lee apparently saw no need for retaining a permanent stable of scouts at his headquarters or creating a more organized and coordinated army-wide intelligence system. Instead, he relied on ad hoc measures and Confederate cavalry to supply information and trusted in his own genius to determine how to use it. For example, when Confederate cavalry failed to keep Lee informed of Union troop movements early in the Gettysburg campaign, he had to take the word of a bedraggled and unfamiliar informant named Henry Thomas Harrison, a scout employed by Lieutenant General James Longstreet who just happened to show up in the right place at the right time with the right information. Harrison’s report spurred Lee into concentrating his dispersed army at Gettysburg, precipitating the collision of the two armies a few days later. Regardless of where it came from, Fishel concluded, Lee could “manufacture conclusions of decisive significance out of very little information or none at all.”
Many Confederate commanders emulated Lee’s overall approach, especially in their reliance on the Confederacy’s very able cavalrymen like “Jeb” Stuart, Colonel John Singleton Mosby, and Lieutenant General Nathan Bedford Forrest to keep them informed. In general, Confederate military intelligence operations, like those in the Union armies early on, were primarily improvised affairs. As the war progressed, however, surviving records do not indicate that the Confederate armies moved toward a more comprehensive, organized, and systematic all source approach to collection and analysis like that embraced by key Federal commanders after 1863. Nevertheless, many believed after the war that the Confederacy had bested the Union when it came to intelligence matters, a flawed perception embellished over the years by the elevation of the Confederate mounted arm to legendary status, the successful surprise attacks at Shiloh and Chancellorsville, and the popular postwar writings of Southern spies like Greenhow and Boyd.
Increased scholarly interest in Civil War military intelligence over the past several decades, however, has helped change this perception and, more importantly, moved the field away from the spy adventure potboiler toward more solid historical studies. Revelations about the significant impact of ULTRA and MAGIC intelligence on the Allied victory in World War II, for example, has undoubtedly spurred interest in examining the influence of intelligence on the outcomes of Civil War battles and campaigns. In addition, recent scholarly emphasis on the Civil War as a people’s war has also drawn attention to the topic. From those who risked their lives gathering military information—including Southern Unionists, Northern Confederate sympathizers, women, and African Americans—to the officers and civilian leaders who interpreted and used it, Civil War military intelligence was, at its very core, a human enterprise shaped by people from all walks of nineteenth-century American life. Therefore, to study the backgrounds, motivations, activities, and fates of those engaged in intelligence work is bottom up history akin to recent treatments of the Civil War’s common soldier. The study of Civil War military intelligence, then, provides yet another pathway into the experiences of the war’s many diverse participants. The shroud of secrecy and mystery enveloping this shadow war, however, makes following their trails a bit more challenging.
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