Communications during battles were supplemented on
the field by signalers with flags, helping to coordinate movements of the armies to
approximate more closely the events of the 1860s.

The system was the work of the Signal Corps
Association–Re-enacting Division, which has been providing 19th century
communications infrastructures for re-enactments since the early 1980s, said Walt Mathers,
the group’s adjutant.

Mathers has been researching the history of U.S.
military communications for nearly 20 years, with help from the staff of the National
Security Agency at Fort Meade, Md., near his home in Glen Burnie, Md.

The telegraph first did military service in the
Crimean War, from 1853 to 1856, where American observer George B. McClellan saw it in
operation. McClellan, while commanding the Army of the Potomac during the Civil War,
created the Signal Corps.

The new medium let commanders communicate quickly
with Washington, and President Lincoln lingered at the War Department’s telegraph
office, waiting for the latest dispatches from the field. But the Signal Corps’
greatest innovation, Mathers said, was perhaps the development of insulated twisted copper
wire that, unlike conventional bare steel wire of the period, could be laced through trees
or draped over fences to provide tactical communications across a battlefield.

The Signal Corps’ flying telegraph units, using
wagons and pack mules carrying reels of insulated wire, could string lines and set up
operators almost as armies shifted positions, giving commanders in the rear nearly instant
communication with officers at the front.

The military telegraphs did not use Morse Code,
Mathers said. “When we send in plain text, we normally use a Federal two-element
system” called Army Dot Code.

It may sound like a Web address, but Army Dot Code
was an electronic adaptation of the binary language already in use with flags. In flag
signalling, much like ASCII code today, each letter is represented by a series of 1s and
2s. The letter B, for instance, is 1221. When using flags, a 1 is signalled by moving the
flag from an upright position down to the signaler's left. A 2 is made by moving the flag
down to the right. In Army Dot Code, dots and spaces are substituted for 1s and 2s.

Both armies used flags for signalling throughout the
Civil War. They were simpler than telegraphs, but operated only in a line of sight. And if
a signaler's own troops could see him, so could the enemy.

The telegraph system at the Gettysburg re-enactment
was historically accurate, Mathers said. Reproduction equipment, including keys and
sounders, were handmade by Edward Trump of Fairbanks, Alaska. The system was set up using
a common ground return. In the 1860s, telegraphers found they could operate over a single
wire if they used the ground to conduct current to complete a circuit. Wires were
connected to galvanized iron rods pounded into the ground, allowing transmission of
signals over a single wire for several miles.

The link between contemporary technology and the
fields of Gettysburg is forged of iron stronger than that of any cannon or telegraph
cable. The American Civil War, which opened with many soldiers armed with muzzle-loading
smooth-bore muskets and saw the adoption of breech-loading repeating rifles, spurred
development in other areas, as well.

The first system of field hospitals was begun, and
surgery and the treatment of disease and wounds advanced rapidly. The first aerial
observations were made using hydrogen balloons. Ironclad warships and even the submarine
saw their first deployments. In many ways, the Civil War marked the start of the modern
Army and Navy.

The greatest difference between the original Civil
War system and the recreated version was also an advantage for the modern cousin—the
1990s network linked both Confederate and Federal commands. Partly because of that
advantage, the re-enactment was better organized than the original battle.