Spycraft

Stranger Than Fiction: The Revolutionary Submarine “Turtle”

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After a season full of historically-inappropriate spy gadgetry (and almost two full seasons of teasing us with cameos in the TURN opening credits), it was truly refreshing to see one of the most famous and most bizarre inventions of the American Revolution in action on the small screen. I’m talking, of course, about the submarine Turtle, invented by Connecticut patriot David Bushnell in the 1770s.

At first glance, the real-life story of the Turtle seems too fantastical to be true. Even its very design – an odd, bulbous, wooden contraption with a small copper tower, detachable gunpowder kegs, and all sorts of hand-cranks, pedals, screws, and knobs – seems more appropriate to the world of Victorian steampunk fiction than the 18th century. It’s no wonder the Turtle has been an object of cultural fascination ever since news of it trickled into the public consciousness. Even today, you can find all sorts of Turtle paraphernalia for purchase: from t-shirts to 1/32 scale models to pre-made 3-D renderings of the 18th century submarine “ready for your game development.”

But beyond its funky quasi-steampunk appeal, there is a whole lot of historical significance ascribed to the Turtle – and for good reason. The US Navy’s historical division (a.k.a. Naval History and Heritage Command) has put together an excellent summary of the Turtle’s military achievements, which you can read in full on their research website devoted to the tiny wooden sub:

replicaturtle
Life size, fully functional reproduction of the submarine Turtle from the Turtle Project, a collaboration between Old Saybrook (CT) High School and the Naval Undersea Warfare Center, Newport, Rhode Island. The submarine, piloted by Roy Manstan, was launched on 10 November 2007 at the Connecticut River Museum in Essex, Connecticut. Source: Naval History and Heritage Command website.

The submersible Turtle [was] the world’s first combat submarine. Named Turtle because its inventor, David Bushnell, believed the craft resembled “two upper tortoise shells of equal size, joined together,” it saw action in the first days of the American Revolution. Designed in 1771-1775 while Bushnell was a Yale College undergraduate, it embodied the four basic requirements for a successful military submarine: the ability to submerge; the ability to maneuver under water; the ability to maintain an adequate air supply to support the operator of the craft; and the ability to carry out effective offensive operations against an enemy surface vessel.

To achieve these requirements, Bushnell devised a number of important innovations. Turtle was the first submersible to use water as ballast for submerging and raising the submarine. To maneuver under water, Turtle was the first submersible to use a screw propeller. Bushnell was also the first to equip a submersible with a breathing device. Finally, the weaponry of Turtle, which consisted of a “torpedo,” or mine that could be attached to the hull of the target ship, was innovative as well. Bushnell was the first to demonstrate that gunpowder could be exploded under water and his mine was the first “time bomb,” allowing the operator of the Turtle to attach the mine and then to retire a safe distance before it detonated.

That’s quite a long list of firsts! In multiple ways, the Turtle was an engineering marvel ahead of its time. Another remarkable feature of the Turtle was its use of bioluminescent fungi as a light source. No, really! Known both then and now as “foxfire,” the phenomenon of glowing blue-green fungus found in decaying wood is documented back to ancient times, and Bushnell was smart enough to see it as a viable alternative to oxygen-sucking candle flames. (If you love ingenious details like these, then I highly recommend you check out the original description of the Turtle’s form and function as written by Dr. Benjamin Gale in November, 1775. It reads like a science fiction novel!)

Omphalotus_nidiformis
Omphalotus nidiformis: One type of bio-luminescent fungus. Foxfire light is often very dim. This photo is the result of a 30-second exposure!

The Turtle’s Maiden Mission

The fact that the American forces had a fully-functional submarine in their arsenal in 1776 is impressive enough – but on top of that, the Turtle’s wartime mission was remarkably complex, especially for an experimental piece of technology. The Turtle was conceived and built not for reconnaissance or stealthy transport, but to blow up enemy vessels by means of attaching timed underwater mines (i.e. small kegs of gunpowder with special fuses) to their hulls. Once again, from the Naval History and Heritage Command website:

Bushnell had devised Turtle as a means of breaking the British blockade of Boston harbor but because of problems with the vessel… the British fleet had departed from that harbor before Turtle was operational. The first attack on an enemy vessel [the British warship HMS Eagle] by Turtle took place in New York harbor in September 1776. Turtle functioned as anticipated, but the attack… did not succeed. Two subsequent attempts to attack British warships were thwarted by navigational issues and tides. Before Turtle could be re-deployed, it was sunk along with the sloop transporting it by enemy fire on 9 October 1776. Although recovered, Turtle saw no further service. Its eventual fate remains a mystery.

Although it did not achieve military success, Turtle was seen by men of the time as a revolutionary development. In 1785, George Washington wrote Thomas Jefferson: “I then thought, and still think, that it was an effort of genius.” The problem with Turtle, as the former head of the Naval Historical Center, Admiral Ernest M. Eller wrote, was Bushnell’s expectation that just one man could “carry out the combined duties of diving officer, navigator, torpedoman, and engineer, while at the same time fighting tides and currents and propelling the boat with his own muscles.”

While a submarine “practical” for warfare with range, power and reliability had to await the coming of the mechanical age, Turtle was an indispensable first step, which made future developments possible.

In short: The Turtle was a truly Revolutionary submarine, and it led to David Bushnell being credited as the Father of Submarine Warfare.  But why did Ezra Lee’s attack fail? This excerpt from Connecticut History’s excellent article on the Turtle explains it, using Lee’s own testimony:

turtleattack
Drawing of the Turtle in action, attempting to drill into the hull of the HMS Eagle. Source: NavSource Online Submarine Photo Archive (see Further Reading section below)

Later [in life], Lee described his unsuccessful attempt to fasten the mine [to the HMS Eagle]. “When I rowed under the stern of the ship, could see men and deck and hear them talk-then I shut all doors, sunk down, and came up under the bottom of the ship, up with the screw against the bottom but found that it would not enter.” Unable to affix the mine and with daylight upon the water, Lee decided to make for shore before the vessel was discovered by passing boats. But it was too late. Guard boats put off from shore in his direction and soldiers mounted the fort on Governor’s Island to catch sight of the strange craft.

Lee writes that he “let loose the magazine [mine] in hopes, that if they should take me, they should likewise pick up the magazine, and then we should all be blown up together…” Ezra Lee did not lack courage, only experience in a craft no one on earth had ever before piloted in action. The mine did explode, frightening off the pursuing guard boat; Lee escaped with his life and with Bushnell’s machine.

bt turtleSo how accurate is TURN’s use of the Turtle in the Season 2 episode “Providence”? TURN scores much higher than usual regarding historical accuracy when it comes to their use of the Turtle! In case there was any doubt, none of the Turtle’s missions involved Caleb Brewster or any part of the Culper Spy Ring whatsoever; if you look at our TURN Historical Timeline, you’ll find that the real-life Turtle set sail two full years before the Culper Spy Ring was even formed.

That said, the show’s incorporation of the submarine into its alternate history storyline was certainly entertaining, and it very closely paralleled pilot Ezra Lee’s original mission of 1776. (The notable exception being Caleb’s success in blowing up an enemy ship with an underwater mine where Lee had failed!)   The Turtle used in the show is a dead ringer for the meticulously-researched 21st century museum replicas, and Caleb even mentions the use of Foxfire as a light source! Regarding Ben Tallmadge and “Davey” Bushnell meeting at Yale: Tallmadge (Class of 1773) was two years ahead of Bushnell (Class of 1775) at Yale, so their educations did overlap by two years. However, since Bushnell matriculated at the unusually ripe old age of 30 and was therefore twice as old as the average Yale student, he may have had less social interaction with his fellow undergraduates than a typical student — so Tallmadge’s line about how he “didn’t know much” about him makes a lot of historical sense, too.

All the Turtles of the World

Bushnell_Turtle_model_US_Navy_Submarine_Museum
Cutaway model of the Turtle in the US Navy Submarine Force Museum in Groton, CT.

If you want to see (or climb into) a Turtle yourself, Connecticut is a good place to start. The State of Connecticut is pretty darn proud of its submarine heritage: During the Revolutionary War, CT native David Bushnell’s efforts found widespread support among prominent Connecticut patriots like Silas Deane and Governor Jonathan Trumbull, who actually ended up convincing George Washington to support the Turtle venture. Modern-day Groton, Connecticut, the “Submarine Capital of the World,” is home to an active US sub base, the nuclear submarine manufacturer Electric Boat, and a museum that houses the first nuclear submarine in the world, the USS Nautilus.

So it’s little surprise that Connecticut is home to at least three full-size Turtle replicas. Two of them reside at the Connecticut River Museum in Essex; one is a cutaway model you can climb in yourself, and the other is a fully-functional reproduction that embarked on its maiden voyage in November of 2007. Another cutaway model, complete with a mannequin of Ezra Lee inside, can be found at the same Submarine Force Museum in Groton, CT that is home to the USS Nautilus.

The Royal Navy Museum in Gosport, England also has a Turtle replica, although their model is likely an older one, given that it’s much more spherical than the more recent, 21st century American replicas.

Finally, I thought I’d end this post by sharing some modern-day Turtle-related News of the Weird. It turns out that not every replica of the Turtle belongs to a museum; at least one of them belongs to an eccentric artist in New York City who found himself in trouble with the authorities on more than one occasion. Observe:

wcbs ledeNo, this isn’t a parody account of a Loyalist newspaper from 1776 — this incident happened in 2007! Philip “Duke” Riley, an artist with a history of embarking on legally-questionable stunts, built a working Turtle replica out of cheap plywood with the goal of stealthily approaching a British ship in New York Harbor (in this case, the Queen Mary II) in order to take pictures for an upcoming art installation. Riley and his two co-conspirators were promptly arrested after the New York Police and Coast Guard swooped in to intercept the little wooden sub. The New York Times (and plenty of other NY-area papers) published a full account of the bizarre and comical event that, like the Turtle itself, is almost too incredible to believe. The usually-stoic NYT wrote that Riley’s sub “resembled something out of Jules Verne by way of Huck Finn, manned by cast members from “Jackass.””

NYpost 2007aug4If you were feeling charitable, I suppose you could argue Mr. Riley was helping to keep the fascinating legacy of the Turtle alive in his own… unique way. On his own website, which has plenty of additional pictures and video of the submarine launch, he claims his voyage helped expose persistent security lapses surrounding New York Harbor. Whatever your opinion of Riley’s “marine mischief,” at least we got to see a replica of a Revolutionary War submarine on the cover of the New York Post, complete with a snarky headline!

There’s so much for to be said about the history of the Turtle and the brilliant innovation that went into it, but alas, there is only so much we can stuff into one blog post! For more Turtle articles, primary sources, sketches, and other resources, see the Further Reading section below.

-RS

Further Reading/Resources on the Turtle:

US Naval History and Heritage Command: Research page on the Submarine Turtle
This page is the online mother lode of primary source documents concerning the Turtle. Several of these descriptions of the Turtle sound like old science fiction novels — they are some of the most easy-to-read and engrossing 18th century documents you’ll ever come across. Be sure to check out Benjamin Gale’s original description of the Turtle in 1775, and Ezra Lee’s firsthand account of his adventures piloting the Turtle in 1776! You can also read post-war correspondence between George Washington and Thomas Jefferson concerning the Turtle.

Connecticut History article: David Bushnell and his Revolutionary Submarine
Excellent article with more detail on Bushnell and the innovations that made the Turtle unique.

NavSource Online: Turtle Submarine Photo Archive
Collection of photos, diagrams, and sketches of the Turtle from a variety of sources.

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Spycraft in TURN: Nathaniel Sackett’s Anachronistic Gadgets (Or: What year is this again?)

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Here’s a rhetorical question for you, fellow TURNcoats: Why make a show about Revolutionary War espionage when the spy technology you focus on most is from the 15th, 19th, and even 20th centuries?

You might reply: “Well… because it’s fun. And I can make a cool story out of it.” Great! That’s certainly a fair answer. But in that case — why would you try so hard to convince people that your story is fact-based and “authentic” to the 18th century when that argument is pretty much impossible to support?

I found myself asking these very questions while updating the TURN Historical Timeline to reflect the events portrayed in the last few episodes (thought admittedly not for the first time). We had to reconfigure the location of a few things on the Timeline this week in order to fit in more events at the tail end of it – two which occurred in the 19th century and one that even occurred in the early 20th century, well over 100 years after the end of the Revolutionary War! (You can check out the updated version by clicking on the image below, or visiting the Timeline page for additional information.)

TURN Historical Timeline version 2.1. Click to enlarge.
TURN Historical Timeline version 2.1. Click to enlarge.

“Nice gadgets you have there. But what happened to the 18th century?”

Historians might ask themselves “What year is this supposed to be again?” while watching TURN for a multitude of reasons (issues with clothing, uniforms, other material culture, language, false historical claims, premature character deaths, etc.) — but for this post, we’re focusing on intelligence history, which is what TURN is supposed to be about.  Heck, they even changed the official name of the show after Season 1 to clarify that the show is all about “Washington’s Spies”!  Thus far, however, TURN’s treatment of Revolutionary War espionage has been erratic at best.

When it comes to spycraft, Season 1 of TURN definitely started off in the right place, featuring period-correct techniques like Cardan grilles and even the original Culper Spy code — exciting, cunning, and historically-accurate stuff!  And TURN’s opening credits have been teasing us for over a year with a silhouette of the Turtle, the world’s first military submarine that actually debuted in 1776. (I’m saving a fuller discussion about the Turtle for later, in hopes that we’ll see it in the show soon.)

TURN opening credits montage final
TURN’s opening credits feature a number of espionage techniques. Some are accurate to the Revolutionary period; others are not. Clockwise from top left: Invisible ink on eggshells, the 19th century “polygraph” machine, a Cardan grille, and the Turtle submarine. View the full credit sequence here: http://www.youtube.com/watch?v=zLFP6yCHUoA

We’ve also seen the occasional use of invisible inks (or, as they were often called in the 18th century, “sympathetic stains”) – but even that element of Revolutionary spycraft has been given a strange and uneven treatment in TURN. Instead of focusing on the state-of-the-art chemical compound developed by James Jay for the use of Washington’s spies (which is a fascinating true story)  the show seems near-obsessed with the novelty of writing invisible messages through the shells of hard-boiled eggs – a centuries-old technique that the Culper Spy Ring never actually used.

In his book Invisible Ink: Spycraft of the American Revolution, John Nagy sums up the origins and functionality of the “egg method” we’ve seen so often in TURN:

In the fifteenth century Italian invisible ink coverscientist Giovanni Porta described how to conceal a message in a hard-boiled egg. An ink is made with an ounce of alum and a pint of vinegar. This special penetrating ink is then used to write on the hard boiled egg shell. The solution penetrates the shell leaving no visible trace and is deposited on the surface of the hardened egg. When the shell is removed, the message can be read. (Invisible Ink, p. 7)

It’s a fascinating technique, and leads to quite a few dramatic (and highly amusing) moments in TURN. The only problem is that, according to the historical record, the Culper spies ever used the egg method — and neither did anyone else in the Revolutionary War, for that matter.  There is no record of the technique ever being used by either side.

But if Season 1’s use of Revolutionary War spycraft was fairly solid with a few aberrations, Season 2 is just the opposite — with anachronistic techniques far outnumbering the period-correct ones thus far.  Nathaniel Sackett’s “spy laboratory,” with its vials and beakers and fantastical super-weapons, is better suited to a steampunk movie than anything resembling the 18th century.  (So is the bearded, blunderbuss-carrying, leather-trenchcoat-wearing version of Caleb Brewster, but that’s a whole other post in itself.)

Now, in terms of making a storyline easy to follow, creating a centralized place as a sort of “spy headquarters” might make sense for a work of historical fiction, even if such a place never actually existed. However, nearly everything we’ve seen featured in Nathaniel Sackett’s anachronistic “spy lab” is from the 19th century – or even later. Besides the never-actually-used egg method discussed above, both of the most prominent examples of spy technology showcased in Season 2 so far were both invented long after the American Revolution was over:

1) John Hawkins’ letter-copying machine, or “polygraph,” Jeffersonpolygraph (mjaS2e3)which Tallmadge uses to forge a letter in the episode “False Flag.” Patented in 1803 – twenty years after the end of the Revolution – Hawkins’ machine greatly facilitated the arduous tasking of letter copying. Thomas Jefferson bought one for himself which visitors can still see today at Monticello. Jefferson was a huge fan of the innovative device, and he later said “the use of the polygraph has spoiled me for the old copying press the copies of which are hardly ever legible.” Before the late 19th century, the term “polygraph” was used to described copying devices like this one. You can read more about Hawkins’ polygraph machine in the Thomas Jefferson Encyclopedia.

2) Nathaniel Sackett’s bogus “lie detector” from the episode “Sealed Fate.” I’m not even sure where to begin with this one. For starters, the modern-day polygraph or “lie detector” wasn’t invented until 1923. Italian scientists (who always seem to be at the forefront of spy technology!) started experimenting with measuring physical responses to lying and truth-telling in the late 1870s – which is still 100 years ahead of TURN’s Revolutionary War storyline. TURN’s version of Nathaniel Sackett must have been a true visionary to be able to throw together a prototype of a machine that wasn’t invented until after World War I. Too bad they decided to kill him off thirty years too early in the show. (Or as another viewer said on Twitter: “If only Sackett had lived. The Continental Army may have had tanks by 1781.”

Even if the bizarre machine wasn’t supposed to be taken seriously, Tallmadge’s use of the faux-polygraph as a form of psychological torture in order to extract information is just as historically inaccurate as the machine itself. We’ve covered the topic of torture extensively here in the blog.  If you haven’t read the original post, you should, but to make a long story short: Torture was very rarely used as a means to obtain intelligence in the Revolutionary War, in sharp contrast to what we’ve seen portrayed multiple times in TURN.

The infamous
The infamous “lie detector” scene was one of TURN’s featured promo pictures on their social media accounts.

Now here’s the frustrating thing: The American Revolution DID have plenty of awesome and innovative spycraft of its own – from creative concealment techniques to cyphers, masks and grilles, invisible ink, flamboyant messengers, and even “strange but true” experimental technology like the Turtle. It’s not as if the writers of TURN are starved for real-life examples of 18th century innovation.  (I’d like to point out that John Nagy’s book referenced above, which only deals with Revolutionary-era spycraft, is nearly 400 pages long.  There’s a LOT of historical material to work with.) It’s disappointing to see a show that was supposed to focus exclusively on Revolutionary War espionage morph into an anachronistic drama that has little regard for the time period in which it takes place — especially when the series started off on a much stronger footing.

Returning to our updated timeline: Season 2 seems to have left the 18th century behind in several other ways as well. In addition to using “futuristic” spy technology, we’ve recently seen real historical characters killed off decades too early and King George III turned into a drooling, raving lunatic long before his first recorded bouts of mental instability.  For all you viewers who were devastated at Nathaniel Sackett’s untimely death, you’ll be pleased to know that in reality, Sackett survived the Revolution intact, dying at age 68 in 1805.  Indeed, he served the contributed to the cause of American independence in a number of different capacities — in addition to his covert operations for Washington, he also was an active member of the Congressional Committee of Safety and later served as a sutler (merchant) for the Continental Army.

sackettintriguing
In reality, Mr. Sackett still had much to offer the young United States after his intelligence activities were over.

Like we’ve said many times before, here at the blog we understand the necessity of shuffling around some historical events in order to present a dramatic narrative that’s easier to follow. Plenty of events in TURN are off by only a year or two, which is reasonable by most people’s definitions. But as the episodes roll on, we’re finding we need to plot more and more events at the extremes of the historical timeline — including major events that play a central role in TURN’s unfolding storylines.  Regarding intelligence history — which is what the entire show is supposed to be about — the most prominently-featured spy techniques of TURN’s second season were never used in the Revolutionary War at all. The evidence strongly suggests that the writers and producers of TURN are increasing their disregard for the historical record as Season 2 progresses.  That’s not to say, of course, that there’s no hope left — indeed, my personal favorite episode of the entire series, chock-full of excellent historically-informed intrigue, occurred after the halfway point of the first season.  (Episode 6 of Season 1, “Mr. Culpepper,” for the record.)  So while the show is in the midst of a rather disappointing trend, there’s still plenty of time left in Season 2 for things to turn a corner. Here’s hoping the 18th century makes a comeback, and soon!

-RS

Spycraft: Download the Original Culper Code Book

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abe code book
Abraham Woodhull flips through his new code book in Episode 7 of TURN: “Mercy Moment Murder Measure.” For the source of the episode title, look to page 2 of the Culper code book.

218 121, readers! With the debut of the (soon to be “Culper”) code book in last Sunday’s episode of TURN, we can now discuss the real code book here in the blog.  Best of all, we’ve got scans of an original copy for you to use for your own personal correspondence, passing of notes in class, Facebook status updates, and other highly important covert operations. (Can you tell I’ve been waiting for this day since early April?)

Thanks to the wonderful folks at the Library of Congress who have digitized a massive amount of George Washington’s papers, anyone can download an original copy of this particular code book and encrypt messages a la Culper to their heart’s content.

These four pages also provide a fascinating glimpse into 18th century American vocabulary. Obviously, the words included in the code book were words Tallmadge thought the spy ring would use most often in its correspondence. If you use the Culper code to encrypt your own 21st-century letters, you might be surprised at the amount of common words (common to us, anyway) that are not included.

This is just one of multiple original copies of the Culper code book, written in Benjamin Tallmadge’s hand.  I should also point out that “Culper code book” is a modern, not contemporary, title.  Tallmadge, with the same obliqueness he used regarding anything related to espionage, referred to the code book simply as a “numerical dictionary.”

Click on one of the four pages below and then click “view full size” for the largest available size. All images courtesy of the Library of Congress, where this copy of the code book resides.  You might want to keep it readily available for future episodes of TURN… or if you’re feeling REALLY ambitious, you can try to decode one of many original Culper code letters found in the LOC’s online collection of George Washington papers.

(If the image gallery isn’t cooperating, you can also use these links to download the full-size images: Page 1, Page 2, Page 3, Page 4.)

For those of you who haven’t spent hours in an archive familiarizing yourself with 18th century chicken-scratch, a very handy transcription of the entire code book can be found on the Mount Vernon website.  If you ARE, however, feeling confident about your paleography skills, you might try to decipher 277, 617, and other smudged or damaged parts of the manuscript. (Obviously this ‘numerical dictionary’ was well used!)

  • A Note on Codes vs. Ciphers

In certain contexts, the words “code” and “cipher” are often interchangeable, and can carry all sorts of metaphorical meanings. But when it comes to spycraft, their definitions are a bit more black and white. The Language of Espionage glossary on the International Spy Museum’s website contains the following simple definitions:

Cipher: A system for disguising a message by replacing its letters with other letters or numbers or by shuffling them.

Code: A system for disguising a message by replacing its words with groups of letters or numbers.

In other words, ciphers usually involve simple substitution — swapping one letter out for one number, letter, or symbol.  Codes are usually more complicated (e.g. one number could represent an entire word, name, or phrase) and require a code book or other device in order to interpret them.  The Culper code book contains both a code (first three and a half pages) AND a cipher (the simple alphabet cipher used to encrypt words that are not included in the code dictionary).

If you love the nitty-gritty details of spycraft, don’t forget to check out our earlier post on the Cardan system and steganography, featuring the beautiful copper grille seen in the pilot episode of TURN. ipdqs!

LU

Spycraft: The Cardan Grille System

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One of the most exciting elements of the TURN premiere is the debut of 18th century spycraft in the form of a shiny copper grille used by Abraham Woodhull to decipher a secret message hidden within a British letter.  Not only is it a dramatic signal of Abraham’s decision to become involved in intelligence gathering — it’s also an authentic, documented method of spycraft used during the American Revolution!TURN01 - spycraft_4  TURN copper grille

 

 

 

 

 

This particular method of secret  message writing is known as the Cardan system, and the copper plate is a version of a Cardan (or Cardano) Grille, named after Girolamo Cardano (aka Jerome Cardan), who invented it in the 16th century. John Nagy, in his book Invisible Ink: Spycraft of the American Revolution, provides a handy description:

[A] Cardano Grille [was] a sheet of stiff material with irregularly spaced rectangular holes which was placed over the writing paper. The secret message was then written in the holes, the grille or mask removed from the writing paper, and a harmless message was filled in around the secret message to camouflage its being there. To read the message, an identical grille or mask was placed over the writing.(Invisible Ink, p3)

When executed successfully, the “dummy” or cover message would be unremarkable enough to avoid raising suspicion that a secret message was contained within it.  A letter authored by a British or Continental officer full of broken or awkward sentences would almost certainly be scrutinized for secret meanings if intercepted by the enemy.  Even then, it’d be nearly impossible to discern the secret message without possessing the matching grille, which makes the Cardan system a fairly secure one.  You need both pieces in order to decipher the real message.

TURN01 - spycraft_1The system was not without its weaknesses, however. The presence of the grille itself is almost guaranteed to arouse suspicion – as we see in the pilot episode when Abraham pulls the copper grille out of its envelope. Only after discovering the grille does he look around for something to match it with.  (For that matter, the grilles were usually stiff paper or cardboard, and not shiny copper sheets that would attract attention and be more difficult to conceal. Paper grilles are much easier to create, and can be folded or rolled up for easier transport.) Abraham was also pretty fortunate to have discovered the correct orientation of the grille on the first try – since there are four possible ways to position a rectangular grille like the one we saw in the show. There’s a slight chance that the reader might take away an incorrect message if they position the grille incorrectly.

Some people expand the definition of the “Cardan system” to include all shapes and forms of message masks, but Cardano’s original method used rectangular cutouts exclusively. Sir Henry Clinton — the British general who appointed John André as his Chief of Intelligence —  used numerous Cardan grilles and message masks in both personal and official correspondence, even as early as 1776.  Many of them still survive in the Clinton Papers which are housed at the University of Michigan’s Clements Library.  The contents of that collection strongly suggest that we’ll see other variations of “masked” messages in future episodes of TURN — so I won’t discuss those just yet.

The Cardan Grille is one of several 18th century methods of spycraft referenced in the TURN opening credits.
The Cardan Grille system is one of several 18th century methods of spycraft referenced in the TURN opening credits.

During the Revolutionary War, the Americans preferred other forms of cryptography (secret writing) over grilles and masks. The Cardan Grille system is more accurately described as a form of steganography: a specific subset of cryptography that involves concealing a secret message within a larger, unrelated message.

This method of secret writing is an ancient one: both the Cardan grille and the usage of the word “steganography” date back to the 16th century. Just because it’s old, however, doesn’t mean it’s obsolete. Steganography is finding new life in our modern age of computers, with messages being subtly slipped into lines of computer code, or even into the arrangement of pixels in a digital image. (And you might even remember an especially amusing example of steganography that went viral and made headlines earlier this year.)

So there’s no denying it — some forms of 18th century spycraft are still alive and well today. I’m definitely hoping to see more excellent examples embedded into tonight’s new episode of TURN.  Stay tuned for another “First Impressions” post after the debut of Episode 2, and don’t forget to follow @spycurious on Twitter for some live tweets during the show!

-RS

Another example of the Cardan Grille system. (Click to enlarge. Source: Wikimedia Commons.)
Another example of the Cardan Grille system. (Source: Wikimedia Commons)