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Battle of Wits: The Complete Story of Codebreaking in World War II

Free Press/Viking: 2000. 448 pp. $27.50/£20

For decades, the code-breakers at Bletchley Park in the United Kingdom, who battled against the German Enigma cipher, were forbidden to talk about their work. It was only in the mid-1970s that the British government declassified Bletchley Park's role in the Second World War, and for the first time it became clear how code-breakers had made a series of brilliant scientific, mathematical and engineering breakthroughs that had influenced the course of the war.

Several books followed declassification, the first being The Ultra Secret by F. W. Winterbotham, who had been partly responsible for the government's change of policy. Other publications include The Hut Six Story by Gordon Welchman, one of the leading figures at Bletchley Park; The Codebreakers , a collection of essays by other Bletchley veterans; Seizing the Enigma by the distinguished cryptography historian David Kahn; and Station X by Michael Smith, which accompanied an excellent television documentary series of the same name.

These and other books were discussed last year in a Royal Society of Literature lecture entitled “Bletchley in Books”, given by the eminent military historian John Keegan. After examining the various approaches of the many authors, he acknowledged that each book had its strengths, but his conclusion seemed to be that there was still room for the ultimate book about the Enigma story.

By writing Battle of Wits, Stephen Budiansky has taken up the challenge, daring to subtitle his book The Complete Story of Codebreaking in World War II. Indeed, Budiansky does not stop at the achievements of British code-breakers; he also attempts to tell the story of their US counterparts, who struggled against Japanese ciphers.

Budiansky, a mathematics graduate and a science writer on diverse topics, begins by explaining how the First World War renewed American interest in military cryptography. When the United States entered the war in April 1917, it was the 27-year-old hard-drinking, womanizing gambler Herbert O. Yardley who persuaded the war department to create a clandestine cipher bureau, which he then commanded.

Yardley maintained his so-called Black Chamber by setting up a company to act as a front, which was secretly subsidized by the state and war departments.

After the war, he demonstrated that he was still worth funding by cracking the Japanese diplomatic codes and reading their bargaining strategy for the 1921 Washington Naval Conference, which had beeen convened to agree limits on shipping. The Japanese declared publicly that they would settle for nothing less than 7 tons of their own shipping for every 10 tons of British and US shipping, but Yardley knew that their fall-back position was 6.5 tons. He advised the Americans and British to refuse 7 tons, and indeed the Japanese caved in and accepted 6.5 tons.

In 1924, the new secretary of state Henry L. Stimson accidentally learned of Yardley's activities and closed down the Black Chamber, later stating that “Gentlemen do not read each other's mail”. Yardley subsequently embarrassed his former bosses by publishing his memoirs in The American Black Chamber, a notorious bestseller.

Despite Stimson's efforts, code-breaking secretly continued under the leadership of William Friedman, America's foremost cryptographer of the war years. His achievements ranged from his pioneering work on the polyalphabetic cipher to the development of a highly efficient randomization process for encryption. This involved throwing a stack of encoding cards in front of a large fan and then picking them up off the floor.

In parallel with the US history, Budiansky describes the development of British code-breaking. The result is a complex narrative that roams across time and space. However, the pay-off is the ability to compare and contrast the code-breaking efforts of the two nations. For example, whereas the British developed electro-mechanical code-breaking devices known as bombes, the Americans relied heavily on well-established IBM punch-card technology. At the end of the nineteenth century, the American engineer and inventor Herman Hollerith had built machines that combined the punch-card format for storing data with an automatic sorter and tabulator. The idea took off after 1890, when the Census Bureau hired 50 machines to analyse census data. Soon after, punch-card machines were used by a variety of businesses to keep track of their operations. In 1911, Hollerith's Tabulating Machine Company merged with two other firms and became International Business Machines.

Friedman's request for punch-card machines to help break codes was initially refused, even though they were already being used by the military for accounting. Eventually, a newly appointed quartermaster-general, who was more used to traditional accounting techniques, stopped using the machines assigned to him, and Friedman was able to have the lease signed over to his code-breaking department.

Many of the encryption systems Friedman encountered were enciphered codes. First, each word would be encoded as a five-digit number. But this alone is not secure, because frequently occurring number groups can be associated with frequently occurring words. Hence, the Japanese would encipher each number by adding another five-digit number from an effectively random list. The IBM machines could check hundreds of messages looking for repetitions, which indicated the rare occasions when the same encoded word had been enciphered in the same way. Such repetitions were the only way to crack enciphered codes.

Because so much has already been written about Bletchley Park, many readers may find the American sections of the book more interesting. It has been well documented how Bletchley Park gave the Allies an advantage in every arena from the Atlantic to North Africa, but much less has been written about the code-breakers at Arlington Hall — a former finishing-school for girls near Washington — who changed the course of the war in the Pacific.

In 1942, American code-breakers, who had cracked the JN-25 cipher, were able to warn of the planned Japanese attack on America's Midway Islands, which meant that the US Navy was prepared. As a result, the Japanese Navy suffered its first defeat in three centuries. The following year, another code-breaking coup allowed American fighter planes to intercept and assassinate Admiral Yamamoto, commander-in-chief of the Japanese Fleet.

It will be interesting to see how librarians catalogue Budiansky's book. Although he does discuss the technology and science involved, Battle of Wits contains long sections of well-written and fascinating military history. Browsers who discover the book on the history shelves might be surprised to find scientific explanations that can be quite intense. Those who find the book in the science section may be a little disappointed by the lack of scientific emphasis, but they should relish the excellent historical detail that puts the work of Arlington Hall and Bletchley Park into context.

The story of cryptography in the Second World War is one of the great scientific tales of the twentieth century. Budiansky has succeeded in telling it with enthusiasm and insight, delivering a book with style and substance.

Author information

  1. Simon Singh is a science journalist and author of Fermat's Last Theorem, The Code Book and The Science of Secrecy.

    • Simon Singh

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