Civil War Spy Tools

Spies obtained military intelligence during the Civil War sometimes at the cost of their lives. Nevertheless, there were innovative and effective spy tools at their disposal. Both sides found ways to send information through enemy territory that told its leaders about enemy strategies and weaknesses. These tools included seduction, hot air balloons, the telegraph and the cipher.

While women would not technically be considered a spy “tool,” they played as vital a role as any piece of spy technology at the time according to H. Donald Winkler's book, “Stealing Secrets.” Women such as Rose Greenhow, Sarah Slater and sisters Ginnie and Lottie Moon were excellent Civil War spies. Women were not seen as threats, and they could turn to seduction to get what they wanted. According to Winkler, they “tucked coded letters into their skirts, dressed as men, pretended to be grieving widows and seduced enemy officials to get and pass information.”

Both sides used hot air balloons to spy on enemy troops. It marked the first time in U.S. history that balloons were used for military reconnaissance. On Sept. 24, 1861, under orders from the Union army, Thaddeus Lowe successfully alighted at Arlington, Virginia to an altitude of over 1,000 feet and telegraphed intelligence on the Confederate troops encamped three miles away at Falls Church, Virginia. Relying on the information Lowe provided, Union guns were able to fire accurately on Confederate targets. The Confederate army's first successful attempt came on April 13, 1862, when Captain John Randolph Bryan first launched a balloon made from cotton coated with varnish in Yorktown, Virginia.

Spies used ciphers to scramble messages. A cipher could be 26 symbols that substituted for the alphabet. Confederate spy and Washington socialite, Rose Greenhow, for example, used a cipher to encode reports that passed through her Confederate network of contacts. Her most notable achievement came in July 1861 when she transmitted ciphered messages with information on Gen. Irvin McDowell's plans to the Confederates. It helped Confederate troops prepare for Bull Run, the first major battle of the war.

The Military Telegraph Service kept secret information moving during the Civil War. More than 15,000 lines were dedicated solely to the transfer of military intelligence. Additionally, commercial telegraph lines were seized for military use in 1861. “Other than telegraphic espionage, the most dangerous service was the repair of lines, which often was done under fire and more frequently in a guerilla-infested country," Maj. Gen. Andrew Greely wrote in an article published in 1911. "Many men were captured or shot from ambush while thus engaged.”