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Long after the end of the Civil War, Henry S. Tafft tried to enlighten some fellow veterans about his service in the fledgling Union Signal Corps. Signal officers, the retired captain claimed, were charged with  “opening communication, scouting, reconnaissance, acting as aides to the generals upon whose staffs they were serving, and supplying information to the commander of the army and navy, until it came to be generally understood that the signal officer was the repository of everything worth knowing, being both omniscient and omnipresent, and was besieged for news accordingly. He was prepared at any moment, night or day, to undertake the most hazardous service.” The signal man, Tafft added, was also sworn not to divulge the meaning behind the “mysterious motions” of the signal flags.

The main responsibility of signal men, of course, was to communicate messages—from one part of a battlefield to another or from ship to ship—through the use of special flags and a secret code. As essential as such a system might seem to be, the United States had never tested one in battle prior to July 1861, when a former U.S. Army officer employed a “Wigwag” system of signals on behalf of his new Confederate employers in the First Battle of Bull Run. With the help of enlisted men (whom he described as being “so stupid that I have to knock them down & stamp & pound them before I can get an idea into their heads”), Captain Edward Porter Alexander—a man known today almost exclusively for his skill as an artillerist—constructed a series of towers near Manassas Junction that gave him a clear view of the surrounding landscape. During the ensuing battle, Alexander detected a developing Union flank attack from one of these heights and signaled the infantry, “Look out on your left; you are turned.” (Alexander, whose signaling work helped assure the Rebel victory at Manassas, later credited Union signal men for delaying—and possibly thwarting—a Confederate assault on Little Round Top during the Battle of Gettysburg.)

Alexander owed his expertise to the system’s creator, Alfred J. Myer, a onetime U.S. Army surgeon with whom he had served in New Mexico prior to the war. Myer sold his idea to the U.S. government, which made him a major and the Army’s lone signal officer in June 1860. Unfortunately for Union Maj. Gen. Irvin McDowell, Myer was unable to bring his flags to Manassas in time for the war’s opening battle, depriving the Union command of a valuable intelligence tool—and Alexander of what could have been an intriguing battle of wits with his former mentor.

Myer’s invention was timely: The telegraph was too slow and unreliable for tactical use, while the sheer size of Civil War battlefields would soon make the use of couriers risky at best. In Myer’s system—which both sides adopted—signal teams (usually an officer and one or two enlisted men) established stations in specially built towers or tall trees. The tools of their trade included a telescope and field glasses (for receiving messages from other stations), collapsible poles, turpentine-burning torches for use at night and flags ranging from 2 to 6 feet in width. Signal men chose their flags—either white with a red square in the center, red with a white square, or black with a white square—based on their surroundings (bright sky, thick woods, etc.) and began each message holding the flag in an upright position. Each subsequent wave or series of waves corresponded to a letter or series of letters in a previously established code. Short messages could be sent and received within 10-15 minutes, and most could be decoded accurately within a range of seven or eight miles.

Neither the Confederate Signal Corps (established in May 1862) nor its Union counterpart (established the following year) allowed for much of a staff. Officers were trained in small signal schools, then assigned to units from which they would draw and train enlisted men to assist them. Service in the Signal Corps was not a free pass from the dangers of the firing line: While the signal man’s high perch made him an ideal spotter for friendly gunners, it also made him a conspicuous target for enemy sharpshooters and artillerists. Service aboard ships was especially dangerous during bad weather.

Signal Corps duty required nerve, and the men with the flags had the respect of the men with the rifles.


Originally published in the December 2006 issue of Civil War Times. To subscribe, click here