The Battle of Monterey Pass: The Signal Corps During the Pennsylvania Campaign

In 1854, Albert J. Meyer was commissioned as an Assistant Surgeon in the Army. In 1856, Meyer drafted a memorandum on a new system of signals and obtained a patent letter on it. Two years later the War Department recognized the possibilities of Meyer’s system and appointed a board to examine it. In 1860, the United States Army adopted the Meyer system of signaling. Because Meyer’s system of signaling used flags that seemed to swing around in no particular manner to the untrained person, the term wig wag was given to the flags.

There were two basic wig wag flags, one flag was a red square with a smaller white square in the center, while the second flag was also square but was all white with a smaller red square in the center. A combination of movements of the signal flag represented a letter. The signalmen would wave these flags while the intended party who was observing these flags would look through a telescope calling out the numbers. Another man would translate the numbers and write the letters down using a cipher wheel. Meyer’s code for signaling was used until 1886 when the international Morse code system was used. After 1896, Meyer’s wig wag system was again used until 1912 and was eventually replaced by the Semaphore flag.

A United States Army signal party could be as small as one officer and two privates. Only the officer in charge was authorized to decipher the code relayed from other signal stations. The officer was responsible for encoding and decoding all messages that were transferred to their station. Enlisted men were responsible for flagging the signals and reading the incoming signals but never the translation. Being communications experts was only one of the signalman’s job duties. They also assisted their commanders by performing reconnaissance and surveillance. The signal corps, using a 12 foot staff and 4 foot flag could signal to their stations a distance of 8 miles, except in rainy or foggy weather conditions. On clear days their signals could be read as far as 15 miles. Weather conditions and time of day signified what color flags were used. At night flying torches, which were special torches fueled with turpentine were used to send signals. Telescopes and field glasses were also an essential part of the signalman’s equipment as well as a cipher disc that was used to encrypt the messages. This disc was actually two discs made of either brass or cardboard, one disc contained the alphabet and the other disc contained numeral combinations. By rotating these discs and changing the alignment of the numbers and letters the codes could easily be changed.

The Union Army’s Signal Corps used Jacks Mountain, Indian Lookout on the Catoctin Mountain, Emmitsburg and Monterey Pass and South Mountain during the Pennsylvania Campaign. Due to the communication and observation advantages, both the Union and Confederate Armies needed to obtain and protect their positions using mountain gaps and overlooks. In July of 1864, from High Rock, Union Signal Corps reported that Chambersburg was burned.

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