Intelligence in the Civil War
Intelligence's New Tools
Thaddeus S. Lowe, a 29-year-old balloon enthusiast, went up about 500 feet on June 18, 1861, looked down upon Washington, and, via a cable linking his balloon gondola to the War Department, telegraphed a message to President Lincoln: “The city, with its girdle of encampments, presents a superb scene….” It was the first wartime air-to-ground communication ever recorded in America. By linking the balloon to the telegraph, Lowe transformed what had been a novel contraption at country fairs into a tool for a new kind of intelligence gathering: real-time aerial reconnaissance.
The demonstration had been arranged, not by military officers, but by Joseph Henry, first Secretary of the Smithsonian Institution, and an enthusiastic supporter of the use of balloons in war. With a note introducing Lowe, Lincoln nudged Lieutenant General Winfield Scott, commander-in-chief of the U.S. Army. The army soon accepted the new tool, forming the U.S. Army Balloon Corps. In March 1862, when Major General George B. McClellan began his campaign up the Virginia peninsula, Thaddeus Lowe, bearing the title Chief Aeronaut, went along. He had three balloons and what he described as an “aeronautic train, consisting of four army wagons and two gas generators.”
At 3 o’clock one morning, Lowe went up and stayed aloft until daybreak, “observing the camp-fires and noting the movements of the enemy” around Yorktown. Brigadier General Fitz John Porter went up next, getting, from 1,000 feet, an unprecedented view of an American battlefield. As soon as he landed, Porter rounded up generals and mapmakers and drew up maps showing the Confederates’ fortifications, based on what he and Lowe had seen while aloft.
Lowe made frequent flights to obtain tactical intelligence. On June 14, 1862, for instance, he went aloft near Richmond carrying a map on which he noted, in red, “some of the most important earth works seen this morning.” The map had been prepared by John C. Babcock and “E.J. Allen S.S.U.S”—the cover name of Allan Pinkerton. The initials stand for “Secret Service, United States,” Pinkerton’s name for the organization he formed while working for McClellan.
As the Union began to make routine use of the new surveillance system, the Confederates reacted. They shot cannons at the balloons, but artillery, aimed by formulas involving trajectory from cannon to land target, could not easily become antiaircraft guns. Confederate artillery officers soon learned that when they shot their guns, they became targets of fire directed by Union artillery spotters in the balloons.
Then, in the age-old rhythm of intelligence, an espionage innovation produced a counter innovation: The Confederates started camouflaging encampments and blacking out their camps after learning that Union balloonists counted campfires for estimates of troop strength. To fool daytime observers, Confederates painted logs black and arranged them to look like cannons jutting from defenses. They were dubbed “Quaker guns” and “wooden ordnance.”
The Confederates raised balloons a few times. But the South did not have adequate equipment for producing large amounts of hydrogen gas or rubber. The first Confederate balloon was made of varnish- covered cotton and was filled with hot air. An observer drew a map of Union positions near Yorktown, but had trouble controlling the balloon. The next Confederate balloon was made of colorful swaths of silk (inspiring the legend that the balloon’s fabric consisted of ball gowns donated by patriotic Southern belles). Filled at Richmond’s municipal gas works, the balloon was tethered to a locomotive, which took it to an observation site. The balloon later was moved by a tugboat and taken down the James River. The tug ran aground, and Union troops captured the balloon.
Richmond map used by Lowe on June 14, 1862, prepared by John C. Babcock and “E.J. Allen”
Both sides soon gave up the use of balloons: the South because of the lack of resources, and the North primarily because Lowe and his balloons could not find a bureaucratic niche in the U.S. Army. Lowe resigned in May 1863, and the U.S. Army Balloon Corps was disbanded soon after.
The telegraph, however, went to war and stayed in the war. The Union particularly saw the value of the telegraph and used it as the key component in what would be the first modern military communication system. Field telegraph units linked commands and were connected to hilltop signalers who sent messages by flags in daylight and by torches at night.
For most of the war, Union Army telegraphic messages were handled by the civilian-staffed U.S. Military Telegraph (USMT), which connected battlefields with far-flung generals and with the War Department in Washington. On a typical day, the USMT operators handled 4,500 telegrams, some more than 1,000 words long. During operations at Fort Monroe, on the Virginia peninsula, the terrestrial network even had an underwater branch that carried messages across Chesapeake Bay to a land connection at Wilmington, Delaware. The underwater link was a recycled, 25 milelong segment of the original Atlantic Cable, which had briefly connected America and Britain in 1858.
The Confederacy also used the telegraph for tactical communications in the field and for messages between Richmond and military commands. Like the Union telegraphers, Southerner operators usually encrypted messages. The Confederates’ preferred encryption system was known as the Vigenere substitution cipher, named after Blaise de Vigenere, the 16th-century French diplomat who developed it. The encipherment depended upon the use of a keyword used to set up a matrix in which a letter acquired different equivalent each time it was used in a message. Union codebreakers cracked the code because Confederates usually employed only a few keywords and encrypted only important words.
For example, in a warning message sent to a general by President Jefferson Davis, the text read: “By this you may effect O—TPGGEXVK above that part—HJOPGKWMCT— patrolled…” The Union cryptanalyst, beginning with guesses, deciphered the first jumble of word as a crossing and the second as the river (words were often encrypted without spaces between them). Knowing the basic Vigenere system, he then worked out the keyword as CompleteVictory, and with this, he could break subsequent messages until the keyword was changed. Keyword changes, however, did not guarantee message security; for by knowing that a keyword had to be 15 letters long, Union cryptanalysts had a solid clue when they tried to break a message. (Union cryptanalysts also helped to break up a Confederate counterfeiting ring based in New York City.)
The cipher system, which gave Confederate telegraph operators strings of letters combined with plaintext, impaired message transmission. The operators, who had no idea what they were sending, often made mistakes. They sometimes garbled messages so thoroughly that only fragments reached decrypting officers.
Both sides learned to tap telegraph lines. Federal operators tapped General Albert Sidney Johnston’s headquarters in Bowling Green, Kentucky and were undetected for a month when they tapped the Confederate line between Chattanooga and Knoxville. Most message intercepts, however, came not through taps, but via the capture of enemy telegraph stations. Once in control of a station, the captors could not only intercept messages, but also send false ones. Robert E. Lee found telegraphing so untrustworthy that he ordered his officers to “send no dispatches by telegraph relative to … movements, or they will become known.” Federal telegraphers scramble words in prearranged patterns, making Union message relatively secure. (The technique was known as “routing code.”)
Much battlefield signaling involved flags and torches rather than telegraph operators. The wig-wag system, as it was known, was developed by a U.S. Army officer, Major Albert James Myer. While he was a medical officer in the 1850s, Myer used his knowledge of sign language to develop the wigwag’s two-part numerical code. A motion of a flag or torch to the left indicated 1, to the right, 2. Each letter of the alphabet was represented by a combination of lefts and rights. As Myer pointed out in his manual, once a “signalist” learned the system, he could use “a handkerchief or hat held in the hand above the head … or any white or light cloth tied to a gun.”
One of the young officers who had worked with Myer was Lieutenant Edward Porter Alexander. When the war began, Myer was still in the U.S. Army, and Alexander was about to become a captain in the Confederate Army. At Manassas in July 1861, Myer, attached to a balloon unit, did not have a chance to put his system in operation. But Alexander did, setting up a wig-wag station on a height still called Signal Hill. Alexander, who spotted the glint of an artillery piece and signaled a crucial Union maneuver, helped the Confederates win the battle—thanks to Myer.
Because both North and South used essentially the same wig-wag system, the signal principles were mutually understood. By training powerful telescopes on rival signal stations, each side could intercept the other’s messages and then try to decrypt them. Once, Confederate signal operators intercepted a message that read, “Send me a copy of Rebel Code immediately, if you have one in your possession.” The Confederates quickly changed their codes. Intercepting and decrypting went on continually. During a campaign around Charleston, the Confederates had 76 signalists at work, twelve of them assigned to reading enemy traffic.
Myer developed a cipher disk, as did the Confederates. The disks were used for important messages. The transmitting station initiated the message by wig-wagging the cipher combination that he would use. The receiving operator received the enciphered message, then deciphered it with the cipher device, which typically consisted of two concentric disks. Numbers on the outer disk indicated flag wags (2122, say, for right, left, right, right). These numbers aligned with letters on the inner ring.
The idea of signaling with flags inspired the sending of other visual messages. Reports of “clothesline” and “window-shade” codes made Confederate and Union officers suspicious of ordinary objects for their possible covert meanings. One documented clothesline code showed whether Confederate forces had withdrawn (empty clothesline) or were being reinforced (three pieces hung out).
In terms of espionage, the signal units of the two sides differed considerably. For the Union, signal intelligence was kept separate from the running of agents and other espionage activities. The Confederacy’s Signal Corps had a clandestine unit, the Secret Service Bureau, whose missions included infiltration of agents into the North. Major William Norris, chief of the Signal Corps, ran the Secret Line, the underground link used by Confederate couriers and agents traveling between the North and South.
The dual nature of the Confederate Signal Bureau was demonstrated at least twice during the war. A Secret Line operative set up a window-shade signal station in a Washington building for communicating with an intelligence officer across the Potomac. The operative was captured, but insisted he was an officer in the Confederate Signal Corps. Held for a time on suspicion of spying, he was later released and returned to the South. In another incident, a Confederate Signal Corps officer was captured while attempting to set up a signal station behind Union lines. The officer “was taken in citizen’s dress,” a Union report noted, although “the rebels have a uniform for their signal corps.” Records show that he was sent back to the Confederacy in an exchange of prisoners of war. So, as a signal officer, he did not meet the fate of a spy.
From Signalman to Weatherman
Albert J. Myer
Albert J. Myer’s lifelong devotion to communications dated back to his youth when he was a telegraph operator in New York state. He graduated from Buffalo Medical College in 1851. His doctoral dissertation was entitled “A New Sign Language for Deaf Mutes,” reflecting his interest in silent signaling.
In 1854, he became an assistant surgeon in the Army and was sent west where federal troops were fighting Indians. Inspired by the sight of Indian smoke signals and hand communications, he developed a “wig-wag” communications system that used flags by day and torches by night. He was campaigning for the Army to adapt his system when the Civil War began.
Myer shifted from surgeon to signal officer, with the rank of major, and was promoted to colonel when the Signal Corps was created in 1863. He clashed with superiors over the administration of military telegraphy, which was not under his control. After eight months in the fledgling Signal Corps, he was assigned to the Military Division of the West Mississippi, where he served for the rest of the war.
When Congress reorganized the Signal Corps in 1866, Myer once more became chief signal officer. He was head of the Signal Corps from 1867 until his death in 1880. During his tenure as chief, he helped to create the U.S. Weather Bureau, which was placed within the Signal Corps. Under Myer as its first director, the Weather Bureau started issuing reports that used the word “forecast” for the first time. Myer became a permanent brigadier general just before his death. Fort Myer, across the Potomac from Washington, D.C., is named in his honor.