The Signal Corps
An Innovative Technology of War
Wig Wag: The Army's "talking flags"
Codes and Ciphers
Flags, Torches and Telescopes
Myer's Manual of Signals stated that with a 12-foot staff and 4-foot flag, signals "are easily read at a distance of 8 miles at all times, except in cases of fog or rain. They are read at 15 miles on days and nights ordinarily clear."
Special torches, fueled with turpentine, were used to send signals at night. One torch was placed in the ground. A flying torch was mounted on the end of the signal staff. By moving the flying torch form side to side relative to the motionless foot torch, the "1" or "2" could be read.
Telescopes and field glasses were an essential part of a signal party's equipment. Union officers were accountable for their equipment and were under strict orders not to let any fall into enemy hands.
A Signal Party on Duty in the Field
Only the officer understood the code, and he was responsible for encoding and decoding messages. The enlisted men would flag the signals and assist in reading incoming signals which were given to the officer for translation. Signalmen were selected by examinations and were generally more educated. Commissioned officers were tested in reading and writing, composition, arithmetic, chemistry, natural philosophy, surveying and topography.
Not only were they expected to serve as communicators, they also assisted commanders with reconnaissance and surveillance by virtue of their location at high points on the terrain and their mobility. The life of a signalman could be behind the lines enjoying good food and the comfort of a commander's headquarters—or in advance of the army exposed to the elements in remote and isolated locations, experiencing hardship and danger.
Signal Stations During the Battle
Gloskoski's Elk Mountain station sent the most famous signal of the battle. Late in the afternoon this party observed Lt. General A.P. Hill's division of Confederates approaching the battlefield after its long march from Harpers Ferry. The Elk Mountain station sent an urgent message to Gen. Burnside, "Look well to your left. The enemy are moving a strong force in that direction."
Confederate signalman were also active during the battle and official maps of the battlefield indicate a CSA signal station was located behind the West Woods.
Did You Know?
Alexander Gardner's photographs of Antietam were the first ever images to show dead soldiers on the field of battle. A New York Times article about the photographs said it was if the "dead had been laid at our doorsteps." More...