Better intelligence turns tide of battle for the North
Historians maintain that Gen. Robert E. Lee and the Army of Northern Virginia lost the Battle of Gettysburg in large part because of the lack of an effective intelligence-gathering capability. This was due to the separation of the cavalry under Maj. Gen. J.E.B. Stuart during the campaign.
What has received less attention is the extensive intelligence apparatus that the Union army had available to help it defeat the Rebel army.
After the Army of the Potomac’s defeat at Chancellorsville in May 1863, Union Maj. Gen. Joseph Hooker knew that he had little time to prepare for another engagement with Lee’s army. For this purpose, he needed to determine the strength, disposition and intentions of the enemy. At the same time, he wanted to ensure that Gen. Lee learned as little as possible about the plans and operations of the Army of the Potomac.
To accomplish these objectives, Hooker had considerable resources in place, including the provost marshal department and its recently established Bureau of Military Information, the Cavalry Corps, the Signal Corps, the U.S. Military Telegraph, special units, and spy networks. Provost marshal
Gen. Marsena Patrick, provost marshal of the Army of the Potomac, was responsible for military intelligence and counterintelligence operations. These duties included directing a team of scouts and spies. He also interrogated Confederate prisoners of war and deserters, as well as escaped slaves or “contrabands” to gather information about the enemy.
Scouts conducted reconnaissance, and spies operated behind enemy lines. Patrick’s counterintelligence duties included tracking down spies within Union lines and local citizens who served as guides for enemy raids and incursions.
When Hooker took command of the Army of the Potomac in early 1863, he ordered Patrick to establish a military intelligence unit. Known as the Bureau of Military Information (BMI), its mission was to collect information about the enemy derived from all available sources, evaluate and process this data, and report the resulting intelligence to the army commander. The bureau
Gen. Patrick chose veteran regimental commander Col. George H. Sharpe, a veteran regimental commander, to direct the bureau, and put him in charge of collecting and analyzing data about the enemy’s strength, disposition, movement and morale. The 35-year-old Sharpe was a Yale-trained lawyer from the Hudson River town of Kingston, N.Y. Sharpe had two capable assistants, John C. Babcock, a civilian, and Capt. John McEntee.
Working as an architect in Chicago when war came in 1861, John Babcock enlisted in the Sturgis Rifles. Allan Pinkerton, the head of Maj. Gen. George B. McClellan’s secret service operation, had recruited Babcock as a mapmaker and an interrogator of prisoners and deserters, skills that proved valuable in future assignments.
Sharpe assigned Babcock as his primary analyst and report writer. The BMI commander selected his other assistant, Capt. McEntee, to lead scout and spy teams in the field, and also to serve as an interrogator and report writer. These three men assumed the responsibility for developing the BMI into an effective intelligence organization.
The BMI would have ample opportunity to demonstrate its proficiency during Lee’s invasion. In addition to its own capabilities, it relied on various other resources to collect information, particularly the cavalry. The Cavalry corps
The cavalry had vital intelligence and counterintelligence roles to perform in addition to its combat mission. These included gathering information for use by the commander and screening the army’s movements from the eyes of the enemy. These roles increased in importance when the army was on the march, and the cavalry’s mobility was a key factor in performing these tasks.
Early in the war, the Union cavalry’s ability to conduct intelligence and counterintelligence operations was limited, because Federal authorities failed to promote the cavalry’s development and military commanders often inhibited its role in the field.
The situation had begun to improve as Lee’s invasion of the North got under way in early June 1863. Gen. Hooker had revamped the cavalry into a single unit in February, about the same time he established the BMI. The reorganization helped create a muchneeded sense of identity among the horse soldiers. The cavalry consisted of a three-division corps with newly promoted Maj. Gen. Alfred Pleasonton in command. U.S. Signal Corps
The units of the Army of the Potomac communicated with each other in a variety of ways, one of which was the “Signal Corps’ wigwag” system, which employed flags during the day and torches at night to send messages by code. In addition to sending and receiving messages, Signal Corps duties included intercepting and translating enemy messages, observing their movements, and engaging in exploring and reconnaissance.
Equipment included flags of different sizes and colors, torches, fuel and other paraphernalia. Since the Federals and Confederates used essentially the same signal code to transmit messages, at times both sides employed ciphers with prearranged keys to secure the contents. The Signal Corps supplemented flag signals with a system of field telegraphy. Portable batteries and magneto-electric generators facilitated use of the telegraph for tactical purposes. Military Telegraph
In addition to the Signal Corps, the U.S. Military Telegraph Service supplied the Army of the Potomac’s communications requirements. The Telegraph Service, essentially a civilian bureau adapted for military purposes, had as its primary mission to ensure that strategic and administrative communications were available to commanders. The Signal Corps, on the other hand, mainly supported tactical operations.
From an intelligence perspective, the telegraph permitted the Army of the Potomac to exchange information with other commands and the government in Washington. The service employed ciphers to enhance the secrecy of communications in the event lines were wiretapped. Special units
The Army of the Potomac had other means for gathering information and denying the enemy knowledge of its strength and movements. In particular, there were sharpshooter units whose main function in combat was to serve as skirmishers forming a defense line in front of the army while recon- noitering enemy positions. They also confronted enemy skirmishers who were attempting to reconnoiter Union lines. Most notable of these special units were the 1st and 2nd United States Sharpshooters, otherwise known as Berdan’s Sharpshooters after their founder and commander, Col. Hiram Berdan.
Another unit with special qualifications available to the Army of the Potomac during the campaign was the Loudoun Rangers. In June 1862, Secretary of War Edwin M. Stanton recruited Samuel C. Means, a successful businessman from Waterford, Va., to organize the independent Loudoun Rangers and assigned him as commander. The Rangers’ mission was to serve as scouts and guides for regular Army units and to counteract Confederate raiding parties in the Northern Virginia area, particularly Mosby’s Rangers.
Couriers, guides and escorts assigned to the Army of the Potomac also performed information-gathering responsibilities. Several units performed essential duties for army headquarters, including the 2nd Pennsylvania Cavalry, two companies of the 6th Pennsylvania Cavalry, and detachments from the 1st, 2nd, 5th and 6th U.S. Cavalry. They scouted the best routes for movement of the army and kept watch for enemy spies and informers operating in or near the Union encampment. Spy networks
ThemovementawayfromtheRappahannock River in Virginia in June 1863 to friendlier regions in Maryland and Pennsylvania meant that the Army of the Potomac could depend more on the local populace for information. During the campaign, a number of civilians actively observed Lee’s troops and informed the Union Army about their movements.
Maj. Gen. Darius N. Couch, the Department of the Susquehanna commander in Pennsylvania, established one group, and Maj. Gen. Robert C. Schenck, 8th Corps commander in Maryland, also sent out civilians in search of Lee’s army. Other operations were being run out of Washington and Baltimore.
These components of a reorganized and upgraded Union intelligence system were in place by mid1863, when the Confederate army began a full-scale invasion of the North. Unquestionably the absence of intelligence because of Stuart’s separation from the main Confederate army undermined Lee’s ability to implement his strategy and tactics. In contrast, Union Maj. Gen. George G. Meade, who had replaced Gen. Hooker, had a sophisticated intelligence apparatus in place that assisted him in gaining a decisive victory at Gettysburg.
Thomas J. Ryan is president of the Central Delaware Civil War Round Table.
Gen. Joseph Hooker’s reorganization of the Union cavalry and an intelligence bureau helped the Union army win a victory at Gettysburg.