Wigwag Signals

Civil War signal flags needed to be seen, yet visibility could invite interception.

Albert J. Myer proposed his visual signaling system to the Army in 1856. The Army dates its adoption to June 21, 1860, with Myer becoming its first signal officer.

Information unfolded over time

Wigwag used one flag to carry ordered movements representing numerals, grouped to stand for letters. The information emerged over time, making the order of movements part of the message.

Flag colors were selected for contrast against the background, helping observers distinguish the movements. The National Park Service also describes varying staff length to improve readability. A color visible against one background might be less distinct against another.

One generic flag repeats along a timeline, with successive motion marks.
An ordered sequence carries information through time.

Seeing and understanding were separate

The National Cryptologic Museum notes that both armies knew the system, so visible messages could be intercepted.

In the NPS account, rotating a cipher disk changed the correspondence between letters and numeral combinations. Encryption sought to protect meaning while transmission remained visible. An observer's ability to see a flag did not establish that they could decipher its message.

Correspondence leads to visible transmission, branching toward a recipient and a possible observer.
Changing correspondence sought to protect meaning without concealing transmission.

Exposure brought another danger

In a letter transcribed by the National Museum of Civil War Medicine, Julius M. Swain described observing enemy movements without exposing his station's flag to sharpshooters. The account does not establish that he encrypted those messages.

Nov 5th 2026 Taylor S.

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