The Man Who Broke Napoleon's Codes by Mark Urban

Author:Mark Urban [Urban, Mark]
Language: eng
Format: epub, mobi
ISBN: 978-0-06-203503-5
Publisher: HarperCollins
Published: 2000-12-31T16:00:00+00:00

Dorsenne’s dispatch was crassly enciphered, as bad in its way as the General Montbrun letter of August 1811 that had proven vital to the breaking of the Army of Portugal code. Given the much greater size of the Grand Chiffre, the damage resulting from this inept staff work was considerably less, but damage there was because this note could be used to begin a substantial attack on the Great Paris Cipher. Mixing in and out of code gives far too much away, an effect that is more pronounced in its original French, since the gender of nouns or form of verbs can reveal much.

Taking the second paragraph, which begins “In the letter of 16th March, 1207 announced 516.1264 was giving, … ” it is fairly clear that 1207 is a person. The construction “announced 516” is also interesting, since the normal use of language dictated the word that must follow. Does 516 mean that, or is it just the letter t, a bigram for th or even a blank, with 1264 meaning that?

A little later on, we see “I would humbly assure 73.516.918 will not …” The code 516 is repeated. The sense of this second phrase is clearly something like: “I humbly assure you,” or HM or the King, whoever, “that …” There seems to be a likelihood 516 does indeed mean that. This becomes all the clearer with what follows this code number. In French, “918 ne negligerai aucune occasion,” the tense and person of the verb to neglect makes it apparent that 918 must mean je, or L Examining the passage, it is clearly a good working hypothesis that 516 means that and 918 I.

As he sat struggling with this puzzle, Scovell’s superb grasp of French grammar and syntax was his best weapon. His ability to absorb language was quite remarkable. Having landed in Iberia with Latin and some Italian, he had quickly obtained a sophisticated grasp of Spanish, noting in his journal following an evening’s entertainment with Spanish hosts just a few months later: “I could easily perceive that the double entendre was the grand substitute for real wit.” With French, he had the benefit of having studied the language for twenty years and was therefore able to fill in the blanks in ciphered passages better than almost anyone else at headquarters could have done.

Going back to the first part of the second paragraph of Dorsenne’s letter, if 516 on its own means that, then 1264 is likely to be another individual. Attacking these passages something begins to emerge: that numbers from 1201 up represent many individuals, names of particular armies and places.

It may be recalled that several months before, when the Grand Chiffre arrived at Joseph’s headquarters, it had consisted of a 1750-type cipher table of twelve hundred numbers previously filled out in Paris. In expanding the table to include terms used in Peninsular warfare (by simply gluing on two farther columns of one hundred numbers each) the staff officers responsible had made the mistake of adding their new codes entirely in the columns marked 1201 to 1400.

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