Tactical Signals Intelligence Originates in World War I

Published with Permission by:
Lori S. Tagg, Command Historian,
US Army Intelligence Center of Excellence, Fort Huachuca, AZ.

After the invention of the radio in the 1890s, the first widespread use of the technology for military communications occurred during World War I.  The ease of intercepting radio messages quickly spurred advances in encryption and decryption of codes and ciphers.  The Military Intelligence Division in Washington recognized the importance of this discipline and quickly established Herbert Yardley’s Code and Cipher Section.  Likewise, shortly after arriving in France, Brig. Gen. Dennis Nolan, the American Expeditionary Forces (AEF) G-2, was forced to acknowledge that the US was woefully unprepared to exploit signals intelligence.  When British intelligence informed him that it had identified two-thirds of the enemy’s divisions through the intercepting and decoding of Germany’s radio messages, Nolan acted immediately.  On July 28, 1917, he tasked Capt. Frank Moorman to form the AEF’s Radio Intelligence Section (RIS), also known as G-2 A6.

Moorman, a 40-year-old Coastal Artillery officer serving as the acting director of the Signal School at Fort Leavenworth, had served in the Military Information Division in the Philippines and had temporarily worked with Parker Hitt, the Army’s foremost authority on codes and ciphers.  When Moorman arrived in France, however, he understood little more than his mission: to read and decipher German radio messages.  Starting from scratch, Moorman soon built a successful collaborative network that provided the AEF with reliable intelligence throughout the war.

Lt. Col. Frank Moorman and his staff of the Radio Intelligence Section, AEF Headquarters (INSCOM photo)

The US Army’s Signal Corps, which had responsibility for Army code compilation and communications security, figured prominently in Moorman’s network.  The Signal Corps’ own Radio Intelligence Service, later renamed the Radio Section, established, operated, and maintained listening stations close to the front lines.  Personnel manning these stations intercepted and copied enemy radio messages around the clock.  The Signal Corps turned recorded messages over to RIS personnel at each Army headquarters for deciphering and analysis using keys provided by the G-2 A6. The most difficult codes and ciphers and potentially important messages were passed further up the chain to Moorman’s section.

The US Army’s first foray into tactical signals intelligence quickly surpassed the efforts of its Allies.  Its eight listening stations intercepted more than 72,000 messages and 238,000 telephone calls.  Additionally, personnel located enemy radio stations, constructed net diagrams, intercepted and located radio signals from airplanes ranging for hostile artillery, policed US Army telephone lines near the front for operational security, and distributed American trench codes.  They also helped develop enemy order of battle through traffic analysis by using call signs and knowledge of German communication protocols.

One early success occurred in December 1917, when the RIS intercepted a transmission indicating the enemy planned a barrage in an area where a US division was co-located with the French.  The RIS passed this intelligence to front line headquarters just in time to allow the Allies to unleash a counter-battery attack that effectively prevented the Germans from carrying out their plan.  Examples like this quickly won over skeptical commanders who initially distrusted the value of code and cipher work. However, it also exposed a vulnerability for future warfare. Moorman cautioned that the system developed for use in World War I was successful primarily because of the static nature of trench warfare.  Its value decreased when the enemy became mobile and the RIS could not maintain close contact long enough to establish the listening stations and install the necessary equipment.

In 1920, Moorman spoke to the officers of the Military Intelligence Division in an effort to pass on insights relevant for the future.  He recalled that his most pressing problem was obtaining adequate personnel: “The difficulty in finding men who could actually think without a guardian was surprising.  It is hoped that one of the aims of the future will be to develop this ability in men chosen for code and cipher work.”

Another obstacle the RIS faced was educating outside personnel about the process of code and cipher work.  “What [headquarters] wanted us to do was pick out the important messages, decode them, and let the rest go.…It was a matter of considerable difficulty to make them see that we had to work them out and that the Germans did not tag their important messages before sending them.”  Additionally, educating troops about the importance of safeguarding their own communications was paramount.  Moorman warned, “It is a sacrifice of American lives to unnecessarily assist the enemy in the solution of our code.”  Too often, soldiers mishandled codes and refused to “[observe] the ‘foolish’ little details that the code man insists on.”  Moorman correctly predicted that all these issues would endure in the future.

US Army’s First Code and Cipher Bureau Created June 10, 1917

Published with Permission by:
Lori S. Tagg, Command Historian,
US Army Intelligence Center of Excellence, Fort Huachuca, AZ.

When Ralph Van Deman established the War Department’s intelligence organization shortly after the US entered World War I, he was faced with building his section from nearly nothing.  Although his background was more in the field of counterintelligence, he readily recognized the need for an office dedicated to cryptology.  He received numerous letters from amateur cryptologists offering their services, but he was intrigued by one person in particular: a bored State Department telegraph operator named Herbert O. Yardley who had deciphered a communication between President Woodrow Wilson and his aide in two hours.  Putting aside concerns about Yardley’s age—he was only 28—Van Deman chose him to create the Army’s first code and cipher bureau, known originally as the American Cryptographic Bureau but most popularly as MI-8.  Yardley reportedly remarked that “it was immaterial to America whether I or someone else formed such a bureau, but such a bureau must begin to function at once.”

Yardley was commissioned a First Lieutenant in the Signal Corps on June 29, 1917 and was given two civilian assistants.  Over the next year, MI-8 grew rapidly to 165 military and civilian personnel working in five subsections:  Code and Cipher Solutions, Code and Cipher Compilation, Secret Inks, Shorthand, and Communications.

Code and Cipher Solutions examined communications from commercial telegraph and cable companies, intercepted radio traffic, and seized mail.  Every suspicious missive, military or civilian, ended up on the desks of this subsection.  In addition to written communications, the section analyzed atypical items like postage stamps, musical scores, religious amulets, even a pigeon’s wings. The amount of work was overwhelming, especially after the US Navy stopped its cryptology efforts and let the Army take the lead.  During the course of the war, the subsection read more than 10,000 messages and solved 50 codes and ciphers used by eight foreign nations. This included the celebrated case in which Capt. John Manley deciphered a coded message found on Lothar Witzke (aka Pablo Waberski), a suspected German spy and saboteur.  Manley’s solution to the code sealed Witzke’s conviction for espionage.

The Code and Cipher Compilation Subsection established secure communications for 40-plus military attachés and hundreds of intelligence officers in the American Expeditionary Forces (AEF).  Its services were critical for several reasons.  First, the Army’s 1915 telegraph code book had been stolen during the Punitive Expedition and had yet to be updated.  Additionally, British cryptologists informed the War Department that German telegraph operators on U-boats were able to copy US messages sent to the AEF and its allies via the transatlantic cables.  Because breaches in US communications would ultimately compromise the whole Allied effort, the subsection revised the entire War Department code and cipher system.  In conjunction, the Communications Subsection operated round-the-clock, averaging the secure transmission of more than 100 sensitive and classified messages per day.

The Secret Ink Subsection established two laboratories specifically for MI-8 use.  Chemists succeeded in developing an iodine vapor reagent for all types of secret inks.  As a result, the MI-8 uncovered communications directing sabotage, which allowed the War Industries Board to implement tighter security measures.  At its peak, the subsection was reviewing more than 2,000 items weekly. As more sophisticated methods to conceal messages were developed, the subsection continually worked on new reagents.

The Shorthand Subsection was an impromptu addition to the organization.  Military censors provided MI-8 with a number of messages believed to be in code but were found instead to be written in shorthand.  The subsection cultivated a community of experts in more than 30 shorthand systems used worldwide.

MI-8’s work was at times exciting and often fruitless, but personnel persevered.  In a series of post-war articles, Capt. Manley stated, “…it is the business of a Cipher Bureau never to allow its interests or energies to flag, for although a thousand suspicious documents may turn out…to be entirely innocent or insignificant, the very next one might be of the greatest importance.”  Manley also stressed that the organization successfully uncovered cases of nefarious activities but also cleared the name of several innocent civilians wrongly accused of spying for Germany.

Although employing relatively simple deciphering methods using little more than pen and paper, MI-8 constituted a significant development for military intelligence during World War I.  Brig. Gen. Marlborough Churchill, the Army’s Director of Military Intelligence, predicted in 1919, “Code attack is indeed still in its infancy.  It is capable of rapid and incalculable development.” Consequently, both the State and War Departments continued MI-8’s efforts as the Black Chamber in the post-war period. Soon thereafter, cryptology evolved into more sophisticated codes and ciphers requiring the invention of mechanical devices that would dominate both Allied and Axis code operations during World War II.

Lieutenant Herbert O. Yardley created the Army’s first code and cipher organization.  By the end of World War I, he had been promoted to Major and oversaw all cryptologic efforts for the US delegation to the Peace Commission in Paris.