Tides of War, Part Two

The first part of this post appeared on the blog in November 2016. The second part was supposed to come out within a week or two, as soon as I found a little more on the post-war use of analog tide-predicting machines. Unfortunately, the search for “a little more” ended up taking way more time than expected and turning up nothing within easy reach. I’d skip the apology if it wasn’t for the fact that the proper references to Anna Carlsson-Hyslop‘s research (discussed in part one) were buried in the source note at the end of this post. Sorry.

Tide-predicting machines, the first of which appeared in the late nineteenth century, were an elegant mechanical solution to a complex mathematical problem. Used mostly to produce information useful to commercial shipping, during the two world wars they also played an important role in the planning of amphibious operations like the Normandy landings.

That contribution is interesting enough to give them a spot in the history of war, but the basic design of the British machines – using multiple gears to create an analog approximation of a mathematical function – also has an oblique connection to one of the most important technical achievements of the war: the mechanization of cryptanalysis.

Alan Turing is justifiably famous for his role in the breaking of the German Enigma cipher, and particularly for his contribution to designing electro-mechanical computing tools that transformed the process. (Even if popular versions of the story do a terrible disservice to the story by erasing everyone except Turing from the picture. Imitation Game, I’m looking at you.) Less well known are some of Turing’s pre-war flirtations with the mechanization of mathematical problem-solving. Andrew Hodges’ biography describes two projects which Turing took on, at least briefly. The first, during his time at Princeton in 1937, was to use electromagnetic relays for binary multiplication to create an extremely large number that could be used as the key for a cipher. This was, as Hodges puts it, a “surprisingly feeble” idea for a cipher but a practical success as far as constructing the relays was concerned.

The second project was an attempt to disprove the Riemann hypothesis about the distribution of prime numbers by calculating the Riemann zeta-function (for the hypothesis and the zeta-function, read Hodges or Wikipedia. There’s no chance of me describing it properly) by showing that not all instances where the function reached zero lay on a single line, as the hypothesis stated. An Oxford mathematician had already calculated the first 104 zeroes using punched-care machines to implement one approximation of the function. Since the zeta-function was the sum of circular functions of different frequencies, just like Thomson’s harmonic analysis of the tides, Turing realized it could be calculated using the same method. Or, more precisely, the machine could rule out enough values that only a few would have to be calculated by hand.

With a grant of £40 from the Royal Society, Turing and Donald MacPhail designed a machine that, like the tide calculators, used meshed gear wheels to approximate the thirty frequencies involved. The blueprint was completed by 17 July 1939 and the grinding of the wheels was underway when the war broke out at Turing joined the Government Code and Cypher School at Bletchley Park.

Nothing in the work that Turing did at Bletchley connected directly to the zeta-function machine, but, as Hodges notes, it was unusual for a mathematician like Turing to have any interest in using machines to tackle abstract problems of this sort. Clearly, though, Turing had been mulling the question of how machines could be applied to pure mathematics long before he became involved in the specific cryptanalytic problems that were tackled at Bletchley.

Of course, the secrecy surrounding code-breaking meant that no hint of the connection, or any of Turing’s wartime work, would have leaked out to those operating the tide-predicting machines in Liverpool or elsewhere. The end of the war meant a return to usual practice, but their strategic importance remained.

Probably the last analog machine to be constructed was a thirty-four constituent machine built in 1952–5 for East Germany (and now in the collection of the German Maritime Museum in Bremen). The Soviet Union had ordered a Kelvin-type machine for forty constituents from Légé and Co. in 1941 that was delivered to the State Oceanographic Institute in Moscow in 1946, on the eve of the Cold War. Bernard Zetler, an oceanographer who worked on tide prediction at the Scripps Institution of Oceanography in San Diego, recalls that he was unable to visit the machine in 1971 because it or its location was classified. The Soviet tide tables certainly were.

The American Tide Predicting Machine No. 2 remained in use until 1966, but played no role in the American amphibious landing at Inchon during the Korean War. The wide tidal range at Inchon meant that the landing needed good tidal information, but rather than making new calculations the existing American and Japanese tide tables were supplemented by first-hand observation by Navy Lieutenant Eugene F. Clark, whose unit reconnoitered the area for two weeks preceding the landings.

When analog machines like Tide Predicting Machine No. 2 were retired, they were replaced by digital computers whose architecture originated in other wartime projects like the ENIAC computer, which had been built to calculate ballistics tables for US artillery. The world’s navies have not relinquished their interest in tools to predict the tides. Their use, though, has never matched the high drama of prediction during the Second World War.

Source Note: The D-Day predictions are discussed many places on the internet, but almost all the accounts trace back to an article oceanographer Bruce Parker published in Physics Today, adapted from his 2010 book The Power of the Sea. Where Parker disagrees with the inventory of machines commissioned by the National Oceanography Centre, Liverpool (itself a descendant of the Liverpool Tidal Institute), I’ve followed Parker. Details on the work of Arthur Doodson and the Liverpool Tidal Institute come from Anna Carlsson-Hyslop‘s work: the articles “Human Computing Practices and Patronage: Antiaircraft Ballistics and Tidal Calculations in First World War Britain,” Information & Culture: A Journal of History 50:1 (2015) and “Patronage and Practice in British Oceanography: The Mixed Patronage of Storm Surge Science at the Liverpool Tidal Institute, 1919–1959,” Historical Studies in the Natural Sciences 46:3 (2016), and her dissertation for the University of Manchester (accessible through the NERC Open Repository). The scientist suspected of Nazi sympathies was Harald Sverdrup, a Norwegian national who worked with Walter Munk on wave prediction methods used in several amphibious landings. Turing’s experiments calculating the Riemann zeta-function appear in Andrew Hodges, Alan Turing: The Engima (1983; my edition the 2014 Vintage movie tie-in).


Elizebeth Friedman, Cryptographer: Part Two

The first twenty years of Elizebeth Friedman’s career as a cryptographer took her to a private research lab, the US Army and Navy, and the Department of the Treasury’s many law enforcement agencies. The start of the Second World War in Europe brought new challenges, starting with the preservation of American neutrality.

With the Coast Guard
The Coast Guard Cryptanalytic Unit began monitoring messages connected to foreign exchange for the Money Stabilization Board in 1938, watching for signs of imminent hostilities so the Board could freeze the funds of the belligerents. Starting in 1939 they also began picking up coded transmissions connected with the two sides. A presidential memorandum gave responsibility for espionage, counterespionage, and sabotage cases to the FBI, but when the Coast Guard turned their intercepts over to the FBI the FBI asked the Coast Guard cryptanalytic unit to solve the codes. The FBI was a relative latecomer to the code-breaking business, having only hired its full full-time cryptanalyst in October 1939. It leaned on the Coast Guard for cryptographic support. The first chief of its cryptanalytic section, W.G.B. Blackburn, was trained by Elizebeth Friedman.

Once the United States entered the war, cryptanalysis began to look like something of a free for all. In addition to the Army, Navy, Coast Guard, and FBI operations, the Office of Censorship, Federal Communications Commission, Weather Bureau, and Office of the Coordinator of Information (the future Office of Strategic Services) all announced that were setting up their own cryptanalysis programs. Thankfully, within about seven months all involved had agreed to centralize code-breaking activities in the Army, Navy (including the Coast Guard), and FBI. The division of labor split clandestine radio messages in the Western Hemisphere between the Navy and FBI and gave the former responsibility for intercepting clandestine communications in the rest of the world. The Coast Guard cryptanalytic unit, now a sub-section of the Navy’s code-breaking division (OP-20-G) continued to focus on these secret messages. It also grew, first to twelve and then to twenty-three people. Elizebeth Friedman was not the commander of the Coast Guard cryptanalytic unit. That role belonged to a commissioned officer, L.T. Jones. After the war she described herself, with perhaps an excess of modesty, as “just one of the workers.”

The ciphers that reached the Coast Guard for decryption came from both individual agents working in secret and substantial radio stations operating out of German embassies. Messages were enciphered using a range of classic ciphers that either replaced (in a substitution cipher) or shifted around (in a transposition cipher) the letters in the message. Most agents were using hand ciphers, in which the message is enciphered using pen and paper rather than a mechanical device. A few used a mechanical device, the Kryha machine, which created a shifting substitution cipher. Agents in Argentina used the same Enigma machine that the German army and navy used to protect their messages (and whose decryption was most recently depicted, with substantial inaccuracies, in The Imitation Game). The Coast Guard was able to use intercepted messages to reverse engineer the wiring that scrambled each letter in the simpler, commercial Enigma machine – those messages turned out to be from the Swiss army. According to NSA historian David P. Mowry this was “the first instance of Enigma wiring recovery in the United States.” Then, with the assistance of British techniques, the Coast Guard team was also able to decrypt messages sent on the Enigma between Argentina and Berlin.

The traffic that the Coast Guard’s code-breaking operation intercepted was never critical to the war effort. Interviewed after the war, Friedman herself suggested that the unit could probably have been better used on other material, rather than working the problem “to the point of overkill” (in her interviewer’s words). Mowry, who wrote a Top Secret history of the topic for the NSA, judged that the US effort to decrypt German clandestine transmissions from the Western Hemisphere had little or no impact on the conduct of the war. Still, American cryptanalysis ensured that nothing snuck up on US operations. Nor was the Coast Guard work Elizebeth Friedman’s only contribution to the war effort. When the Office of the Coordinator of Information was created, she also developed its first code systems.

A Long and Varied Career
Cryptography has such a long history that it’s sometimes hard to remember that large government code-breaking organizations are such a new development. Elizebeth Friedman entered the field at the moment those organizations were being created. Without schools or training programs, cryptographers were few and far between. While her husband spent his career with the Army and the National Security Agency, creating the institutions that would perpetuate the government’s cryptanalytic programs, Elizebeth worked far and wide. Between when she left Riverside Laboratories and when she retired from government service, she worked for or taught at seven of the sixteen members of the current US Intelligence Community (Army, Navy, Coast Guard, Central Intelligence Agency, Department of the Treasury, Federal Bureau of Investigation, and National Security Agency). Her career was not only remarkable for its scope but also probably unrepeatable. By the time she retired, these agencies were on their way towards the extensive permanent organizations that exist today. Retirement was also not the end of Elizebeth’s involvement in cryptography. She consulted for the International Monetary Fund on creating that agency’s secure communications and published a book, The Shakespearian Ciphers Examined (with William Friedman), on their work studying Shakespeare’s works for hidden codes.

Source Notes: The NSA’s history office commissioned several relevant histories as part of its Second World War series. One by Robert Louis Benson, The History of U.S. Communication Intelligence during World War II: Policy and Administration, covers the various organizations; two others, both by David P. Mowry, cover German Clandestine Activities in South American in World War II and The Cryptology of the German Intelligence Services (available amalgamated here). Some of Friedman’s own comments in an oral history interview with Benson (online here) were also useful.

Elizebeth Friedman, Cryptographer

Elizebeth Smith Friedman. Courtesy NSA Photo Gallery at https://www.nsa.gov/about/photo_gallery/

Elizebeth Smith Friedman. Courtesy NSA Photo Gallery.

In 1999 the National Security Agency induced William F. Friedman and Elizebeth S. Friedman into the agency’s Cryptologic Hall of Honor. Husband and wife, William and Elizebeth were two of America’s leading cryptanalysts – code-breakers* – for almost forty years. They were rarely a husband and wife team: respect for the security restrictions that surrounded code-making and code-breaking meant they could almost never discuss their professional work. US Army public affairs describes William as “a legend in the cryptology world – his painstaking work, prolific writings, and brilliant accomplishments set a standard in the field that has yet to be challenged.” One of the early leaders of the Army’s Signals Intelligence Service and then of the NSA, Friedman’s work was recognized with the Medal of Merit by President Truman and the National Security Medal by President Eisenhower.

Though much of her work was a matter of public record long before that of her husband’s was declassified, Elizebeth Friedman never received the same recognition during her lifetime. Her own path as a code-breaker was far more unusual and circuitous.

First Steps
A graduate of Hillsdale College in Michigan, Elizebeth Smith Friedman was introduced to both cryptography and her future husband when she was hired by Colonel George Fabyan to work at Riverbank Laboratories, an eclectic research center Fabyan operated on his estate. Fabyan believed that Shakespeare’s plays had been written not by William Shakespeare but by Sir Frances Bacon, and so – alongside other, more practical pursuits – Riverbank employed several researchers searching for codes within the texts that would prove Baconian authorship. Elizebeth was one of them, and while William had been hired to work on other projects for Fabyan he soon became involved as well.

During the First World War, the cryptographers at Riverbank were used by the US military to break enemy codes and teach cryptography and William was commissioned into the US Army. Having soured on Fabyan’s approach to the Baconian question he left Riverbank after the war and moved to Washington and to Army’s code and cipher unit. Elizebeth moved with him. After a year working for the Army and another working for the Navy, Friedman resigned to stay home. Her daughter Barbara was born in 1923 and her son John in 1926 (see his birth announcement here). A year later, in 1927, she went back to full-time government work.

Fighting the Rum War
Until the post-Second World War centralization of signals intelligence, any agency involved in law enforcement, national defense, or international affairs might hire its own code-breakers. At the Department of the Treasury, the need was driven by the demands of Prohibition and the fight against the illegal liquor trade. Under the Volstead Act of 1920 it had become illegal to make, import, or sell alcohol in the United States. In response, rum-runners began to smuggle alcohol in from Canada, Mexico, the Bahamas, and the French islands of St Pierre and Miquelon. The rum-runners’ ships were fast and many of them were well-organized in substantial syndicates such as the Consolidated Exporters Corporation of Vancouver, BC. US Customs, the Coast Guard, and the Bureau of Prohibition – all agencies of the Treasury – worked together in an attempt to stem the tide.

In 1925 the Coast Guard began intercepting radio transmissions between rum-running vessels and their organization. With only the help of one part-time decoder, the number of undecoded messages quickly began to build up. Elizebeth Friedman began working on the messages in 1926 and the next year the Treasury Department’s Bureau of Prohibition hired her as a full-time consultant, or special agent. As a consultant, Friedman did not need to conform to standard office hours. Instead, she could collect messages and information from the Coast Guard’s Washington headquarters and take them home to solve the codes.

In 1928 she moved to the Bureau of Customs, then in 1930 to the Coast Guard to form a permanent cryptographic unit for the Treasury. Between 1927 and 1930, Friedman not only decrypted messages sent by the rum-runners but also taught code-breaking to Coast Guard personnel as the agency’s intelligence department expanded from two officers to a well-staffed operation with regional offices in New York and on the Pacific and Gulf Coasts.

Unlike code-breaking for the military or intelligence services, Friedman’s work for law enforcement often came into the public eye. Friedman was frequently called upon to testify in court as an expert on codes and ciphers, in at least one case using a blackboard to offer an impromptu lesson in cryptography to demonstrate how the bootlegger’s cipher functioned. These appearances also led to unwelcome media attention, much of it – Friedman later complained – plain wrong. Her memoirs show a deep distaste for much of the newspaper coverage of her appearances, and particularly for sensationalism and inaccuracy.

CG-100, one of the "Six-Bitters, 15 Feb. 1928. USCG Photo No. 34363 by Joseph N. Pearce.

CG-100, one of the “Six-Bitters, 15 Feb. 1928. USCG Photo No. 34363 by Joseph N. Pearce.

Coast Guard intelligence did not restrict itself to using shore stations to intercept and decode the radio messages being sent by the rum runners. Starting in 1930, the agency also experimented with intercept operations afloat. William Friedman was seconded for two weeks from the War Department Signal Intelligence Division, where he now worked, to the Coast Guard cutter CG-210. A fast 75-foot patrol boat built to chase rum-runners, CG-210 was equipped not only to intercept coded transmissions but also to take direction-finding fixes on the transmitters. While he was aboard, William could provide real time intelligence on the rum-runners’ operations. The operation was successful and soon the Coast Guard equipped six of these fast ships, known as “six bitters,” with intercept and direction-finding gear. Signals intelligence was on its way to becoming, in the words of the Coast Guard Commandant, “the most important single item combating rum [running].”

The Life as an Itinerant Code-Breaker
Compared to her husband, hired by the War Department in 1921 and employed continuously there or at the NSA until his death in 1969, Elizebeth Friedman’s code-breaking career was far more intermittent and circuitous. Though all Civil Service classifications were open to women after 1920, most were in low status positions. The employment of spouses in the Civil Service would become more tenuous when the Economy Act of 1932 prioritized the spouses of Civil Service employees for dismissal in case of cutbacks.

Cryptography, on the other hand, was a wide-open field – there were no formal schools, no professional standards, and no existing hierarchies that might keep Elizebeth out. The area was so new,and so irregular that she could even take her work home. In the field, she was recognized as a leader. Writing in her later years, Friedman recalled that:

with one exception, all of the men younger or older who have worked for me and under me and with me, have been true colleagues and have never been obstructionists in any way … It was likewise true of the court officials and attaches, the judges and the United States Attorneys, the Customs Officials, and numerous other officials with whom I came into contact at the times I was called as an expert witness, that I have never received anything but the utmost courtesy and in many cases often admiration. Their astonishment at the work I had been able to bring to a conclusion which was a powerful means of supporting the battle they were fighting was, I think, the greater, because I was a woman (from her unpublished memoir, page 66)

Beyond the Rum War
The end of Prohibition in 1933 was not an end to the Coast Guard cryptanalysis unit or to Friedman’s career. Though the staff shrunk again to a low of five in 1937, Elizebeth and her colleagues continued to work against alcohol and narcotics smuggling. The start of the Second World War in Europe in 1939 brought fresh responsibilities for preserving American neutrality – and the beginning of a new phase in Friedman’s cryptographic career.

* Strictly speaking, a code obscures the plain text by substituting full words while a cipher substitutes individual letters (or bi- or trigrams), but I’m not being precise in my use of the two words. Likewise for cryptography (the creation of codes or ciphers) and cryptanalysis (the breaking of codes or ciphers).

Part Two of this, on Friedman’s Second World War career, is here.

Source Note: Elizebeth Friedman’s memoirs and numerous photos have been put online by the George C. Marshall Foundation, who also hold her husband’s voluminous papers. Intelligence operations against the rumrunners are discussed in an NSA historical pamphlet and a book published by National Intelligence University Press. The details of Elizebeth Friedman’s career differ between the three; in trying to reconcile them I’ve tended to follow Friedman’s memoir but I make no claims to my correctness.