During the American Revolution a complicated system of hidden Spy networks, interpersonal relationships, scientific knowledge, personal cunning, guile and risk taking helped win the war.
It’s hard to imagine that the fate of the American cause would rest so heavily in the hands of a tailor, an enslaved double agent—or a judge’s wife who sent surreptitious signals on her laundry line. But as General Washington struggled to win a war with an army that was perpetually undermanned, undertrained and undersupplied, he relied increasingly on his unseen weapon: a secret intelligence network. Throughout the war, Washington’s spies helped him make bold, canny decisions that would turn the tide of the conflict—and in some instances, even save his life.
Washington’s underground spy network helped Americans win their revolution. Secret agents, invisible ink, ciphers and codes—the gritty and dangerous underworld of the colonial insurgency is replete with intrigue: letters written in invisible ink.
A rare female agent who went by the mysterious moniker Agent 355; and the gruesome execution of the patriot spy Nathan Hale. General Washington was deeply involved in intelligence operations.
From the beginning of Washington’s meteoric rise, intelligence gathering helped shape his military career. He first learned to use on-the-ground information from Native Americans and deserting French soldiers during the French and Indian War. Intelligence, he learned, could make the difference between victory or death.
In 1775, when the Second Continental Congress chose Washington as commander in chief of the Continental armies, Washington appointed a soldier named Thomas Knowlton to organize the war’s first spy unit. The roughly 130-man group, known as “Knowlton’s Rangers,” played a key role in the 1776 battle of Harlem Heights in New York, scouting out the British advance guard. In the blazing musket fire of the skirmish that followed, Knowlton was killed, his place in history cemented. Even today, the seal of the U.S. Army intelligence service bears a “1776” stamp, in honor of his unit.
The Revolution
During the Revolutionary War, both the British and the Americans used invisible ink. The British used both organic fluids and common sympathetic inks. Major John Andre, the chief British intelligence officer, had agents put a letter in the corner of their correspondence to inform the recipient as to how the hidden secret message could be developed; for example, an “F” was placed in the corner of letters that could be revealed by fire, an “A” for those that needed the application of an acid.
But George Washington wanted something more, an ink that could only be revealed by a unique, specially formulated reagent. Sir James Jay answered the general’s call. Jay, brother of American patriot John Jay and a physician that dabbled in chemistry, created a “sympathetic stain,” which he supplied to Washington. Washington would then pass it on to the Continental Army’s spymaster, Major Benjamin Tallmadge who in turn provided it to the members of the famous Culper Spy Ring: Abraham Woodhull and Robert Townsend. To avoid suspicion, Washington instructed his spies to write seemingly banal letters between the lines of their secret messages, or to inscribe them “on the blank leaves of a pamphlet. . . a common pocket book, or on the blank leaves at each end of registers, almanacks, or any publication or book of small value.”
Ciphers and secret codes were used to ensure that the contents of a letter could not be understood if correspondence was captured. In ciphers, letters were used to represent and replace other letters to mask the true message of the missive. The letter’s recipient utilized a key--which referenced corresponding pages and letters from a well-known book, such as Entick's Dictionary--to decode the document’s true message. Some spy groups even created their own pocket guide to serve as a cipher’s key. Similarly, some letters were written in intricate secret codes where numbers and special characters replaced letters, a method most notably practiced by the Culper Spy Ring.
Invisible Ink
One form of secret writing used by both the British and American armies was invisible ink. During the Revolutionary War invisible ink usually consisted of a mixture of ferrous sulfate and water. The secret writing was placed between the lines of an innocent letter and could be discerned by treating the letter with heat or a chemical substance. The recipient placed the paper over the flame of a candle or treated it with a chemical reagent, such as sodium carbonate, which would reveal the letter’s hidden contents.
James Jay, the brother of John Jay and a physician practicing in England at the time, created a chemical solution out of tannic acid to be used as an invisible ink, and supplied quantities of the stain to the colonists. George Washington himself instructed his agents in the use of what was referred to as the "sympathetic stain," noting that the ink "will not only render. . .communications less exposed to detection, but relieve the fears of such persons as may be entrusted in its conveyance." Washington suggested that reports could be written in the invisible ink "on the blank leaves of a pamphlet. . . a common pocket book, or on the blank leaves at each end of registers, almanacks, or any publication or book of small value.”
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"Secret Reviled"
Congratulation, you decifered one of Washingtons Spies Invisible ink!
FINAL LOCATION N 40° 41.898 W 074° 31.302