The Signal Corps:Battlefield Communication–Civil War

Battlefield communication has always been difficult. Before technology, armies relied on bugles, trumpets, drums and regiment flags to signal to the soldiers what was to come next. But as men spread out in fighting, it made these forms of communication very difficult to use.

During the Civil War, these methods continued to be used, but a new type communication system was introduced as well. The new method used flags (and at night, flaming torches) to communicate across distances.

The process wasn’t simple. The Army created the Signal Corps to handle this process. The men needed to carry flags, staffs, and torches. And in each location, they needed a high piece of ground or a lookout tower from which to signal. Because soldiers from both the Union and the Confederacy learned forms of the flag system, the messages needed to be sent in code. To establish the cipher, men carried a disc “dial” system that could change the cipher as needed so that the code could not be hacked.

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The Signal Corps

The flag system for sending signals was created by Albert James Myer (1828-1880). Myer worked in telegraph offices growing up. He was aware that both the Army and the Navy had been looking for improved communication methods. However, the methods attempted had been complex or involved cumbersome equipment. In the early 1850s, there was no agreed-upon system. 

Albert Myer went on to medical school but was still captivated by nonverbal ways to communicate. When he wrote his thesis for medical school, he created a sign language that he felt would be useful for the deaf. From this work, he began to develop a system for the military.

Because Myer’s system was created in the 1850s before the country had splintered apart politically, Myer made no effort to hide his work. In order to test it, he also required volunteers to help out. Though he ultimately fought for the Union, the flag system he worked on was first used by Confederates in the South. Some of those who assisted him retuned to their home states in the South, taking Myer’s ideas with them.

Use of Flags

The concept of a flag being used to signal troop movement sounds simple enough, but the method Myer developed was actually quite complex, partly because every message needed to be encrypted.

In general, there were three basic flag signals used. A wave to the left signaled “one,” a wave to the right signaled “two,” and a wave forward signaled a break between words or messages. Certain flag waves were determined for each letter of the alphabet so that words could be spelled out. For example:
A is one, two, or 1, 2.
B is one, two, two, one, or 1221.
C is two, one, two 212, and so forth.

When spelled out, the messages ranged from “Enemy approaching from the South” to complex messages concerning future strategy.

Signal Corpsmen often sent several messages, one right after the other.  A gun fired once indicated a first message; two shots indicated the start of a second message, etc.

Any very important messages were to be verified. The receiving station was to send back the same message. This process assured the sender that everyone agreed on what the instructions had been. 

Signal Corps Equipment

Signal Corps members carried with them a staff and two flags. During the day, the men knew that the flag color that was most visible was a white flag with a red square. However, if there was snow on the ground, a black flag was used.

The corpsmen also carried a torch to use for nighttime signaling. When using a torch, the operator placed a second torch at his feet as a reference point to clarify the signals. To better receive messages, members of the signal corps all carried high-powered telescopes.

Since both sides based their system on Myer’s idea, they realized that if the enemy could see the signals, they could probably interpret the conversation. One of the tools signal corps members carried was a two-disc device that permitted them to “dial” different codes. By signaling to the recipient what cipher the corpsmen were using, those who needed to would be able to decipher the messages.

How to Attract Attention

The Signal Corps faced some interesting challenges. How does a corpsman attract the attention of someone to whom they want to signal?

Signaling for attention ranged from running back and forth to flag waving. (from “A Manual of Signals: For the Use of Signal Officers in the Field,” 1864.

A government instruction booklet from 1864 explains that attempts to attract attention “should never be abandoned, until every device has been exhausted; and they should be renewed and continued at different hours of the day and night…”

These men often worked in isolated observation towers built for them by the military. By putting the signal corpsmen up high, they were more visible. In areas where the fighting had been going on for a prolonged time, the towers were spaced so that each tower could be seen by the next one. That way messages could travel by relay from tower to tower. If there was no time for building a tower, the men clambered up rocks or climbed trees. In desperate circumstances, signal corpsmen sometimes moves out in front of the troops so more people could see them. Mortality was high.

Signaling for attention ranged from running back and forth to flag waving.

“A Manual of Signals: For the Use of Signal Officers in the Field,” 1864.

Other Ways of Communicating

Anyone who has read the Civil War novel, Killer Angels by Michael Shaara, may remember the opening chapter. A lone rider was assigned to scout the military movements of the other side. Because these “spies” rode alone, they were less likely to draw attention of the other army. This way they could report back as to troop movements. 

The spies (or scouts if they were in uniform) rode through potential battlefield areas. They noted the topography, observed troop movement, and talked to townspeople to pick up any information the locals had gleaned as to the plans of the enemy.

Military orders were sometimes sent by courier. These written notes sometimes went from brigade to nearby brigade, but often they were sent over much longer distances. These missives generally also were sent in an agreed-upon code in case they were intercepted.

Telegraphs Used in Some Places

The telegraph was introduced in this country in 1835-36. By 1861, a private telegraph company, Western Union, had wired the U.S. from coast to coast.

The system used wires that could carry Morse code signals. The telegraph was so popular that the Signal Corps attempted to arrive in an area and string telegraph wires in advance of any fighting. This permitted them to communicate with the nearest headquarters.

Balloon Surveillance

The military was also beginning to look to the air. Thaddeus Lowe, a self-made aeronautics expert, was experimenting with big hot air balloons before the war. In July of 1861, Abraham Lincoln appointed Lowe Chief Aeronaut of the Union Army Balloon Corps.

These hot air balloons were primarily used for general surveillance of an area. Lowe or one of his men rode in the basket with a telescope and report back on the enemy. Balloons were also used occasionally during battles. However, they were difficult to transport, so they often couldn’t reach the location in time.

In a unique combination of two innovative services, Thaddeus Lowe convinced Union Major General George B. McClellan to permit him to attempt to relay information via telegraph—from a balloon. In 1862, the Army of the Potomac led by McClellan pushed south to the outskirts of Richmond. Working behind Union lines, Lowe guided a tethered balloon up about 2,000 feet in the air from which he observed the actions and movement of the Confederates. The balloon carried a telegraph with wires that were strung to the ground, so the telegraph operator traveling with Lowe relayed in signals everything Lowe saw.

Very Different Today

Today our military has access to many ways to observe the enemy. From unmanned drones that fly reconnaissance missions to satellite imagery and infrared sensors that detect enemy presence, modern technology permits battles to be plotted by GPS and tracked and fought via computer in ways that earlier military units could not even imagine.

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For m ore on military communications, see Bugle Calls and the Origin of Taps.

For more about the Civil War, see Elizabeth Thorn: Burying the Dead While Pregnant. Or read about some of the mascots that accompanied the soldiers: Dog Jack, Mascot and Volunteer for the Union Army.

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