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timeline: 1775
world of influence
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photo: actual spy letter
A letter written in invisible ink by Benjamin Thompson on May 6, 1775
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Espionage and counterespionage were as commonplace during the 18th century as they were in the 20th century during the Cold War. During the Revolutionary War, spies for both England and America obtained and transmitted information about troop movement, supplies, fortifications, and political maneuvers. Loyalists in America (or Tories as they were often called) were happy to provide secret information to the Crown, and British sympathizers with the colonists' cause helped funnel information to the American forces. Even Benjamin Franklin's son William, who was a loyalist, spied on his own father and reported the elder Franklin's activities to the British authorities.

Throughout Franklin's tenure as America's first diplomat to France, he was surrounded by spies. In fact, Edward Bancroft, the secretary to the American delegation, was a spy for Great Britain. Bancroft provided British authorities with a tremendous amount of information concerning the Americans' plans, negotiating points, who they met with, and what was discussed. Bancroft's role as a spy was not made public by the British until almost a century after he died.

The Second Continental Congress created the Committee of Secret Correspondence in 1775, which was charged with gathering intelligence and "corresponding with our friends in Great Britain and other parts of the world" to gain information that would be helpful to the American cause and to forge alliances with foreign countries. Benjamin Franklin was one of the original members of this committee, which was the forerunner of the CIA.

Like modern secret agents, American and British spies during the American Revolution used a number of methods for hiding and transmitting information, including invisible ink, secret codes, blind drops, and other "technology." Here are a few of the methods they used:

Invisible ink: Several kinds of invisible inks were used by both sides during the war. One type was activated with heat and others by various chemicals. The invisible message was usually written between the lines of another letter, which would appear to be totally innocent. Upon receipt, the reader would either heat the letter over a flame or put it into a chemical bath to reveal the hidden message.

Codes: A code would be set up that used letters or numbers to stand for other words. In order to decode the messages, the recipient needed a key or code book. Ciphers were another type of code. In its website, "Spy Letters from the American Revolution," the Clements Library at the University of Michigan describes a cipher method that the notorious Benedict Arnold employed:
Benedict Arnold used a cipher to deliver his messages secretly to John André. The cipher's key was a standard published book, either Blackstone's Commentaries on the Laws of England or Nathan Bailey's Dictionary. When Arnold composed his letters, he first found the word he wanted to write in the key. Instead of writing the word directly in the letter, he wrote down the page number, the line number, and the number of the word counting over from the left. Therefore, each secret word was represented by a series of three numbers.
Other Methods: Letters or messages would be left at a "blind drop," which was a location that was agreed upon in advance, such as a park bench or hollow tree. The message would be left by one person to be picked up later by another. Sometimes messages would be cut into slivers and stored in the hollow stem of a quill. Hollow silver balls or "bullets" were also used to store and carry messages. Not much larger than a musket ball, these balls could be easily concealed, or even swallowed if the messenger were captured.


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