French Ciphers during the Reign of Louis XIV

Louis XIV's Great Cipher is well-known by Bazeries' codebreaking and his hypothesis about the identity of the Man in the Iron Mask. The present article is an attempt to provide a broader perspective to codes and ciphers during the reign of Louis XIV.

(0) Ciphers used by ambassadors (1650-1676) ... figures 1-99 with diacritics etc. (another article)

(1) Louvois' Code/Cipher (1676) (DE=150/228/280) ... entries up to 300

(1B) Cipher for Envoy to Bavaria (1679) ... entries up to at least 496

(1C) D'Avaux's Cipher (1684) (DE=321) ... entries up to at least 505

(2) Codes/Ciphers (1689) (DE=365/DE=171) ... entries up to about 471; low numbers reserved for single letters

(3) Another Code/Cipher ... entries up to about 417; low numbers reserved for single letters

(4) Louis XIV's Code/Cipher (1690, 1693) (DE=202) ... entries up to at least 420; low numbers reserved for single letters

(4B) Louis XIV's Code/Cipher with Ambassador in Rome (1690) ... entries up to at least 535; undeciphered

(5) Louvois-Lauzun Code (1690) (DE=143/205/297) ... entries up to 451

(5B) Seignelay-Lauzun Code (1690) (DE=CXIII) ... entries up to at least 816 and Roman numerals

(6) Code/Cipher (1691) Broken by Bazeries (DE=34/42/97)... entries up to about 587

(7) An Unbroken (?) Code/Cipher for Catinat (1691) ... entries up to at least 366; Unbroken

(8) A Great Cipher (1690) ... entries up to at least 898

(8A) Two Codes for Peace Negotiation at Rijswijk (1696-1697) with Provision for Code Switching ... 500/378 entries

(8B) Louis XIV's Code for Marquis d'Usson and a Similar Code (April 1702) (DE=311/DE=311/331)... 540/560 entries

(9) An Unbroken Code of Catinat (September 1702) ... entries up to at least 464

(10) Code between Guelders and Rheinberg (November 1702) (DE=21/87/135) ... entries up to at least 383

(11) Code related to the War of the Spanish Succession (ca.1702-1704) (DE=4u) ... two-digit, letter-digit, letter-letter combinations

Louvois' Ciphers Preserved in BnF fr.6204

Observations on Codes/Ciphers during the Reign of Louis XIV

(1) Louvois' Code/Cipher (1676)

(DE=150/228/280) Mémoires et correspondance du maréchal de Catinat, Tome II (1819) (Google), p.343-352, includes a code of October 1676, which was sent by Louvois, Minister of War, to a M. de Bonnais. While this is a relatively small code of 300 entries, it has its merit in its non-alphabetical arrangement of entries (i.e., it is a two-part code). The following is a part of its decoding table.

Generally, it assigns three numbers to single letters and two numbers to syllables (consonant+vowel). A few frequent words are assigned one to three numbers. Eleven numbers are reserved as nulls.

Louvois' Code Management Instructions

Louvois' instructions accompanying this code is no less interesting than the code itself. The code was to be kept sealed until further instructions were received from the King, unless the receiver was attacked by an enemy (at the time, France was at war with the Dutch, allied with the Imperialists (Wikipedia)), in which case the receiver was to report the news with the code. The packet was also to be opened when letters, encoded with a code different from the current one, were received from a place attacked by an enemy. In any case, when the receiver opened the packet, he was to report the reason to Louvois. Except for these specified cases, the receiver must not open the packet and must be ready to return it when Louvois required it at the end of the campaign, even if it would be given him again.

The instructions show the French court was aware that unnecessary use of a cipher would compromise its security.

The war with the Dutch ended in 1678 with the Treaty of Nijmegen. From 1688 to 1697, France was again at war (the War of the Grand Alliance, recently called the Nine Years' War by scholars).

(1B) Cipher for Envoy to Bavaria (1679)

An image of a letter of 15 November 1679 from Denis de La Haye-Vantelet, French envoy to the Bavarian court at Munich, is available on a website for France-Bavaria cooperation.

It has entries up to at least 496, probably representative of letters and syllables plus a few names/words.

The following is my provisional transcription.

Le Mr? de Bauiere auoit
362 388 445 369 200 399 15 374 363 364 435 3?14
naturellement l'ame basse et timide
461 263 346 403 361 431 413 347 336 314 367 200
Il auoit este eleue par une mere
399 286 374 460 38 247 224 388 394 388 374 376
austrichienne plure passionnee pour
235 200 388 374 244 224 457 38 378 385 406 45 496
la Maison d'ou Elle sortoit que
239 379 39 350 265 223 239 30 330 201 306 351
pour les propres enfans M. le Duc
356 235 374 458 350 284 365 333 255 333 235 45 227
de Bauiere Maximilien auoit
354 318 365 445 369 315 435 306 283 237 306 318
reconnu par la suite po des temps
418 235 466 200 399 286 374 235 288 398 394
que la Maison d'Austriche apres
263 316 286 337 420 337 311 383 365 458 241

The content is interesting in its unkind remarks about the late Elector of Bavaria (Wikipedia), who had died in May 1679 and whose mother was from the House of Austria.

(1C) D'Avaux's Cipher (1684)

(DE=321) The cipher used in a letter (DECRYPT-WEB) of comte d'Avaux, French ambassador in The Hague, to Louis XIV dated 9 January 1684 was recovered by George Lasry (George Lasry, "Deciphering a Letter to Louis XIV from his Ambassador to the Dutch Republic, le Comte d'Avaux, 1684" in HistoCrypt 2021 (pdf)).

The cipher is similar to Bethune-D'Estree Cipher (1689) below. Actually, the breakthrough came when Lasry, who had found that d'Avaux's letter of 1688 employed Bethune-D'Estree Cipher (1689), tried a possibility that "instead of A, B, C, being 20, 22, 24 as in the 1688 code, the letters of the alphabet start from 10, that is, A=10, B=12, C=14." He proceeded with the assumption of a similar code structure. When a partial plaintext was obtained, he found that the letter is a famous one in Dutch history of this period.

The above-mentioned letter, intercepted and now at the Dutch Royal Archives (KHA Prins Willem III, XIII-I), caused sensation when published by the Prince of Orange.

The War of the Reunions (1683-1684) (Wikipedia) had broken out by the French troops taking some towns in the Spanish Netherlands. It was like a continuation of the War of Devolution (1667-1668) and the Franco-Dutch War (1672-1678), in which Louis XIV was the aggressor trying to push the northern and eastern borders to a defensible line. The Spanish had declared war on France in the hope of inducing their allies to join forces. Prince William of Orange, leader of the Dutch since 1672, was willing enough, but Amsterdam, ever critical to the authority of the prince, was against any involvement in the war. William accused the town of being in secret communication with d'Avaux. At this timing, d'Avaux's letter of 9 January 1684 was intercepted (by the Governor of the Spanish Netherlands according to the Prince's account). On 16 February, William disclosed the deciphered letter to expel the delegates from Amsterdam. (Baxter (1966), William III, p.190)

According to Lasry, in this letter, d'Avaux detailed his dealings with the burgomasters of Amsterdam, who wanted concrete assurance from Louis XIV. The Governor of ths Spanish Netherlands provided the decipherment to William. (I wonder whether the codebreaker was the author of the treatise on the art of deciphering described in another article.) The deciphered text was published in several pamphlets including an initial version with incomplete decipherment, an updated, more complete version, and even an English version. D'Avaux in turn published a pamphlet on "La fausse interpretation qu'on a voulu donner à sa Depesche volée", in which he claimed that the text was deliberately distorted for propaganda purposes and even provided his version of some sentences in question.

Lasry confirmed that the text published by the Dutch was correct by comparing it with his own decipherment. While William was not always law-abiding, it is now established that he did not forge anything on this occasion.

(2) Codes/Ciphers (1689)

Bethune-D'Estree Cipher (September 1689)

(DE=365) The code used in a letter of 6 September 1689 from the Marquis of Bethune (a French emissary to Poland) to Cardinal D'Estree had entries at least up to "471 se", with low numbers up to about 64 being reserved for single letters. While the assignment of numbers are not alphabetical, words with the same initial letter tend to occur in the same row (i.e., the same ones digit). Possibly, the original cipher did not provide separate tables for encoding and decoding but only introduced some irregularity in a one-part code. The sign "+" represents "s".

A line placed below a figure indicates some imperfection or varied termination but these are occasionally neglected. For example, "335" is "Cardinal" but with an underline under "5", it may read "Cardinau" to form part of the plural form "Cardinaux". Similarly, "181 Pologne" may be used to form "Pologn-ois" and "177 France" to form "Franc-ois". "221 service" may read "servi" to form part of "servir." This feature identified by Wallis is clearly seen in the Great Cipher (1690) below.

This cipher was also used in letters of comte d'Avaux, ambassador in the Hague in 1688 (Lasry (2021)).

Teil-Louis XIV Cipher (July 1689)

(DE=171)A letter of 8 July 1689 by Callet de Teil, a judge of the Parlement sent to Poland, to the King of France used a code which is similar to but different from the one above. It had entries at least up to "471 fi". Numbers 14, 16, 18, 20, 24, 28, 30, 34, 36, 38, 40, 44, 46, 48, 50, and 52 are nulls. 10, θ, and κ delete the preceding number. 6', 8', and 9' repeat the preceding number. Symbols like ч ... ч delete everything in-between.


By arranging the elements in a table in which figures run vertically and code elements run horizontally, the regularity of the code can be seen. More over, it is clear that the Teil-Louis XIV Cipher of July 1689 has a very regular assignment, with proper names assigned in the last two and half columns. The Bethune-D'Estree Cipher of September 1689 starts the alphabetical arrangement in the middle of the table.

See another article for more details of these codes.

These were both broken by English mathematician John Wallis. Although more than 450 entries of these codes was superior to 300 for Louvois' code of 1676, these codes have weaknesses compared to the latter. In particular, lower numbers were reserved for single letters and probably Wallis first attacked sequences of such low numbers. Further, the arrangement of these two codes was not completely random but had some regularity in that entries with the same initial letter tend to appear in the same row.

(3) Another Code/Cipher

John Wallis and the idea of a universal library has a photo of the last page of one French cipher Wallis deciphered. As with the above, it has symbols to "signify what is between is to be deleted"and a symbol to "delete that next before it." The arrangement and size are also similar to the above.

371381391 temoi401 tout411 temps
374384 ca394 ce404 ci414 co
375 et385395405415 entre
376386 France396 faveur406416 faveurable
377 il387 jour397 interest407 intention417 imperieux
378 mariage388398 Moscovie408418
379 proposition389 Prince399 par409 pouvoir419
380390 royaume400410420

(4) Louis XIV's Code/Cipher (1690, 1693)

(DE=202) Louis XIV's secret instructions to Castaignere, French ambassador in Constantinople, dated July-August 1690 printed in Paul Rycaut, History of the Turks (Google), p.453 ff, use a code with figures up to 420. The present author partially decoded the letters and reconstructed the code (see another article). It is similar to the above. In particular, lower numbers are reserved for single letters and bigrams etc. having the same initial letter have the same ones digit.

The same code is used in Louis XIV's dispatch of 9 June 1693 printed in David Kahn, The Codebreakers, p.168. (Actually, the present author used this as a clue to decode the 1690 encoded instructions.)

Some statistics of the 1690 letters in code may be useful.

In plaintext French, the most frequent letter is "e", followed by "a", "s", "i", "t", "n." In those letters encoded in this code, the most frequent code group is 53 (s, 48 times), followed by 202 (de, 43 times), 59 (u, 33 times), 98 (re, 30 times), 185 (la, 28 times), 38 (n, 28 times), 50 (r, 27 times), 14 (e, 25 times), 2 (a, 25 times), 3 (a, 23 times), 54 (s, 23 times), 167 (pa, 22 times), 51 (r, 21 times), 83 (en, 20 times). The relatively low rank of "e" can be explained by the fact that syllables such as "be", "ce", "de", ... are assigned their own code numbers.

Two-group sequences occuring 6 times are 119 59 (vo u), 298 80 (ti on), 3 59 (a u), 331 38 (co n), 59 54 (u s), 98 50 (re r) and those occurring 5 times are 14 51 (e r), 167 53 (pa s), 202 185 (de la), 59 51 (u r). (data)

(4B) Louis XIV's Code/Cipher with Ambassador in Rome (1690)

Louis XIV's secret instructions to Charles d'Albert d'Ailly, Duke of Chaulnes (Wikipedia), French ambassador in Rome, dated 10 July 1690, use a code with figures up to 535. The letter is presented on a French website.

Chaulnes had been sent to Rome in 1689 upon the death of Pope Innocent XI (Wikipedia), who had been opposing Louis XVI's measures to control the episcopal sees in France (see Gallicanism and droit de régale in Wikipedia).

The letter, partly in cipher, has not been deciphered. In part, it reads:

... vos lettres des 8, 12 et 17 juin qui m'informent de toutes les diligences que vous avez faites pour 201 459 170 523 172 381 433 201 10 508 141 140 527 523 132 309 493 386 306 403 201 203 403 30 142 et 309 433 27 509 102 433 22 306 180 204 201 ....
dont mesme vous me mandiez que 65 23 89 458 493 507 524 180 325 et que vous croyez 370 106 457 170 513 10 306 201 509 443 107 83 356 310 481 469 523 170 409 433 172 137 313 20 488 446 22 190 42 62 523 434 170 309 477 379 152 491 132 523 20 300 457 307 535 306 180 124 122 396 65 327 65 381 488 172 487 142 70 371 170 201 168 48 47 535 200 107 130 51 488 310 370, 2x 306 172 434 22 488 141 458 22 3x 141 485 22 306 180 306 170 434 22 170 180 152 491 77 190 182 196 107 508 488 312 141 142 98 436 23 10 446 481 306 408 140 355 356 172 449 509 524 98 404 12 32 141 140 506 524 172 20 190 ceux qui ont assisté à l'assemblée de 1682 et ....

Frequent symbols:

170 14x
22 12x
306 12x
488 10x
180 9x
172 8x
10 7x
201 7x
12 6x
433 6x
523 6x
23 5x
141 5x
190 5x
434 5x
20 4x
107 4x
446 4x
481 4x
509 4x
32 3x
47 3x
65 3x
77 3x
89 3x
98 3x
122 3x
140 3x
142 3x
152 3x
309 3x
310 3x
381 3x
409 3x
491 3x
508 3x
524 3x

Bigrams: 306 180 4x; 22 306 3x; 12 32 2x; 523 172 2x; 118 434 2x

Full Data: frequency, frequency (in descending order),

While I was writing this section, discussion of this code started in Klausis Krypto Kolumne.

(5) Louvois-Lauzun Code (1690)

(DE=143/205/297) Harry Thompson, The Man in the Iron Mask prints in the appendix a letter in a French cipher that John Wallis could not solve (see another article). It is one of the letters from Louvois to Lauzun in Ireland (27 May 1690), written about a month before the Battle of the Boyne. The following is a portion of it.

J'accuserais par cette lettre la reception de celles que vous m'avez fait l'honneur de m'escrire ....
.... vous recommandoit de continuer a en(voyer) sa (Majeste) tousjours de mesme 176 134 89 65 132 34 3 200 84 379 360 281 140 26 366 262 102 192 79 76 291 15 37 297 110 243 45 401 422 317 121 69 205 26 23 221 143 303 359 88 156 79 4 41 275 403 409 237 97 316 406 216 383 180 65 394 40 421 7 216 310 381 375 244 433 222 39 419 173 132 146 340 65 385 196. ....

This has a number as high as "862" but, apart from this single instance, 478 is the highest number.

Wallis could not decipher this, probably because numbers for single letters were not assembled in lower numbers but scattered around the whole, as in the 1676 code above.

(Norbert Biermann solved this by finding the key in the archives in 2020. The cipher has entries up to 451, in which not only syllables and words/names, but also letters are mixed in random order. (In the ciphertext printed in the Japanese edition of Harry Thompson, not only is the single highest number "862" a typo for "262", but also the second highest number "478" is a typo for "348.") For details, see Norbert Biermann, "'I Suspect Somewhat of Peculiar in His Way of Ciphering'" (Universität der Künste Berlin, DOI).)

(5B) Seignelay-Lauzun Code (1690) Broken by John Wallis

(DE=CXIII) While John Wallis could not break Louvois' code used in four letters to Lauzun, he managed to break the code used in a letter to Lauzun from Seignelay, Secretary of State for the Navy after the death of his father Colbert. Unlike the Louvois-Lauzun Code above, the arrangement of the entries are generally alphabetical. A slight complication is the use of Roman numerals as well as Arabic figures. Thus, "CIX" is "coste", while "109" is "avec". (Wallis deciphered this as "avec." Norbert Biermann's paper (2020) quoted above shows where Wallis' deciphering was different from the actual reading found in the deciphered copy.)

(6) Code/Cipher (1691) Broken by Bazeries

(DE=34/42/97) Seven letters from Louis XIV or Louvois to General Catinat were encoded with a two-part code with entries 1-587. The code was broken by Etienne Bazeries, the achievement leading to a hypothesis about the identity of the legendary Man in the Iron Mask (see another article).

As with the 1676 code, the arrangement is non-alphabetical and single letters are scattered among the whole. It assigns one (q) to seven (e, i/j, n, s, t) numbers to single letters and one to three numbers to syllables (consonant+vowel). Frequent words are assigned their own numbers. (But "un/une" is not given its own entry.)

Some statistics of a letter encoded in this code (Louis' XIV to Catinat, 14 September 1691, see another article) may be useful.

The most frequent numbers are 42 (de, 110 times), 22 (en, 107 times), 124 (les, 97 times), 125 (ne, 85 times), 145 (la, 80 times), 97 (de, 74 times), 34 (de, 66 times), 503 (pour, 63 times), 337 (la, 62 times), 117 (ra, 61 times), 9 (re, 61 times), 47 (que 60 times). The most frequent two-group sequences are those for "les en" (14x), "en ne" (12x), "mon arm" (12x), "que vous" (12x), "fi cu" (10x), "de la" (10x), "cet te" (10x), "don ne" (10x). (See statistics: (1) encoded text, (2) frequency (descending order), (3) two-group frequency, (4) two-group frequency sorted by frequency.)

(7) An Unbroken (?) Code/Cipher for Catinat (1691)

Mémoires et correspondance du maréchal de Catinat (1819), p.283, also includes a coded letter from Feuquières (Wikipedia), dated "De Pignerol, ce.25 janvier 1691." This appears to be encoded with a different code from that of Louis XIV and Louvois.

Émile Burgaud, Étienne Bazeries, Le Masque de fer (1893) (see another article) claims that Bazeries (in the third person) deciphered this (p.272), though no information on the content is disclosed. (The reference to "Veillane", a place taken by the French (p.19), could have been drawn from Mémoires (1819) and p.57 says no one including "the author" (probably referring to Burgaud) had been able to read it.)

The highest number used is 366 (hence called a small cipher in Le Masque de fer). The most frequent numbers are 91 (12 times) and 44, 51, 78 (11 times each). Sequences occuring multiple times are "44 200", "151 310", "301 151" (3 times) and "5 44", "51 63", "51 81", "57 78", "60 52", "60 300", "63 135", "65 91", "78 44", "78 181", "81 91", "91 22", "99 84", "101 193", "101 229", "129 44", "150 301", "156 99", "157 91", "210 51", "229 255", "235 60", "255 243", "300 57", "310 235", "317 101" (2 times).

De Pignerol, ce.25 janvier 1691.
72 22 57 280 355 296 32 217 181 229 78 44
200 300 106 175 51 151 15 99 84 316 129 205 21
68 31 71 317 101 188 44 347 210 51 81 91 157
91 22 98 56 300 5 254 93 156 84 184 22 104 78
4 37 52 177 44 250 192 60 300 57 78 188 212
275 147 72 241 146 200 54 257 280 145 41 111
179 205 82 134 27 60 63 44 200 52 222 194 101
24 84 21 93 78 44 200 99 72 224 252 266 5 44
234 333 147 100 310 235 243 4 9 145 188 122
47 237 99 84 122 78 47 80 51 336 60 52 150 301
151 310 235 60 247 32 71 164 200 65 56 150
113 263 177 19 184 50 199 144 91 42 151 343
156 99 71 165 301 151 310 56 278 25 355 42
164 24 32 258 47 334 65 21 63 59 65 91 22 60
52 266 214 144 150 263 129 44 101 113 90 22
164 21 310 148 51 168 46 263 195 32 56 25 366
125 51 63 22 83 188 4 78 110 85 72 310 328
280 300 266 216 197 129 44 138 21 83 82 32 34
90 263 251 28 40 46 144 110 47 157 91 44 210
51 81 91 21 172 322 22 200 147 84 241 71 106
51 237 47 101 229 255 243 350 59 213 68 56 60
300 57 234 4 71 143 76 51 341 91 251 132 257
43 84 57 78 235 21 249 86
65 32 5 240 113 101 193 263 25 150 301 151
310 100 91 113 78 150 71 37 181 101 229 255
243 311 91 43 51 241 57 154 300 90 91 184 108

78 181 318 191 60 81 237 322 46 280 153 78
113 51 310 200 333 114 283 362 44 184 181 172
27 243 292 341 343 56 231 154 81 71 177 156
154 250 143 91 156 99 133 59 52 353 71 78 181
65 63 113 280 258 88 266 317 183 271 110 200 5
44 51 63 135 24 279 178 60 25 99 47 63 135 145
243 310 136 304 65 91 317 101 193 235 60 342
103 190
Je suis, monsieur, très-véritablement et avec beaucoup de respect, votre très-humble et très-obéissant serviteur,

(8) A Great Cipher (1690)

Wikipedia has an image of a part of a great cipher from 1690, which has a number as high as "898 le Baron de". As with the above, entries beginning with the same letter tend to have the same ones digit. Four numbers are assigned to vowels and "&" and two numbers are assigned to consonants and frequent syllables ("luy 848 239", "ma 868 298").

Further, the same number can indicate several variant forms. For example, "15" is "genera,l,ux", meaning either "genera", "general", "generaux"; "249" is "oc,casion", meaning "oc" or "occasion"; "822" is "quart,ier,s", meaning "quart", "quartier", "quartiers", "quarts". This characteristic is also seen in ciphers from the Napoleonic age.

(8A) Two Codes for Peace Negotiation at Rijswijk (1696-1697) with Provision for Code Switching

Two extant codes from 1696-1697 are described in Jörg Ulbert, "Zur Verschlüsselung französischer Ministerialkorrespondenzen" in Geheime Post (2015). It was for use during negotiations for the Peace Treaty of Rijswijk (Wikipedia) (1697).

Figures are used to represent single letters, syllables, and words. One of the two codes had entries 1-500 and the other had entries 1-378.

These two codes were intended to be used alternatively in the same message. They are given identifying numbers "379" and "720", which can be used to indicate to the recipient which cipher is used first. See another article.

(8B) Louis XIV's Code for Marquis d'Usson and a Similar Code (April 1702)

(DE=311) Lambeth Palace Library preserves French coded letters of April 1702 deciphered by the British (MS 930, no.9-10 and no.4).

Letter from Versailles, 4 April 1702

This appears to have been written by a minister of the Sun King.

This code employs a very similar scheme to that of the code used in 1690 and 1693 (see above). Low numbers are for the most part reserved for single letters (ordered alphabetically). Numbers 110 and upwards must have been arranged in a table as shown in the image below, in which the code numbers run line by line, while the entries in each column are generally arranged alphabetically. This allows one and the same table on a sheet of paper to be used for both encoding and decoding, while introducing some irregularity to the arrangement.

From the placement of the sequences ca-ce-ci-co-cu and qua-que-qui-quo-quu, the original table may have ended with 539, to which some additions may have been made in the margin.

In addition to the numerical code, the letter employs several roman numerals (such as xxi, xviii, xlvii (undecoded) for some names).

The most frequent code groups in the letter are: 92 ("s", 123 x), 311 ("de", 82 x), 91 ("r", 79 x), 510 ("ce", 59 x), 516 ("que", 59 x), 247 ("re", 56 x), 30 ("e", 56 x), 22 ("a", 55 x), 184 ("la", 48 x), 190 ("au/av", 40 x) (data).

Letter from Louix XIV to Marquis d'Usson, 5 April 1702

(DE=311/331) This is very similar to the code used in the letter of the day before. The top-left portion of the nomenclature (i.e., the code part) even seems to be identical between these. Except for 596(quelque), which may be an error for 546, the range of code numbers must have been 1-559. (See the placement of ca-ce-ci-co-cu and pa-pe-pi-po-pu in the image below.) The word "ennemi" (which provided Bazeries with a breakthrough) is given a code number "222."

The most frequent code groups in the letter are: 46 ("s", 50 x), 331 ("de", 44 x), 44 ("r", 34 x), 174 ("le", 31 x), 20 ("e", 26 x), 347 ("se", 23 x), 466 ("que", 20 x) (data).

Historical Background

The War of the Spanish Succession between France and Spain on one part and the grand alliance of England, the Dutch, and the Emprror on the other was about to officially begin by declaration of war in May 1702 (though hostitilies had already begun in 1701 in Italy).

Hanover and Celle (subdivisions of Brunswick-Lüneburg) were on the side of the allies, while Wolfenbüttel (the elder subdivision of Brunswick-Lüneburg) was ruled by brother dukes Anton Ulrich (Wikipedia) and Rudolph Augustus. Anton Ulrich allied himself with the French and planned to take the duchy of Celle. Hanover and Celle prevented this by a pre-emptive strike in the night of 19-20 March by marching into Wolfenbüttel (Ragnhild Hatton, George I, p.88-89).

The 4 April letter was written upon receiving letters of 21 and 23 March after the first report of the march on Wolfenbüttel from another source ("343" not decoded). The recipient appears to be a commander in some places which might be attacked (possibly Marquis d'Usson below). The letter assures the recipient the King's approval of his conduct and tells that the King would write to him his intensions separately.

William III of England, the architect of the grand alliance against France, had died on 19 March (Gregorian calender). The information was not yet confirmed in Versailles and the writer mentions that if the information was wrong, he would start a war at once and anyway the death might not change the plan of the allies.

The King's letter of 5 April is addressed to Marquis d'Usson, who commanded the Duke of Wolfenbüttel's troops etc. and resided at Wolfenbüttel with the character of a minister (Cole (ed.) (1733), Memoirs of Affairs of State Containing Letters (Google), p.411; the marquis is also mentioned in Vault below).

It was written in response to the marquis' letters of 19, 21, and 23 March about the operation of Celle and Hanover. The King promised relief of Wolfenbüttel in case of war He also instructed the marquis to urge the dukes of Wolfenbüttel to maintain the French alliance but indicated some concessions.

(9) An Unbroken Code of Marshal Catinat (1702)

An undecoded letter of Marshal Catinat of 15 September 1702 is preserved in the library of Canton of Aargau, according to the 1 May 2016 entry of a cryptology blog Klausis Krypto Kolumne. It begins as follows.

137 20 393 97 323 41 269 291 10 28 22 254 13 277 88 43 93 30 271 106 61 296 85 40 84 229 328 109 247 101 22 54 56 163 106 305 350 228 30 217 8 33 50 171 188 209 214 335 314 13 198 368 130 433 101 ....

The highest number is 464. The most frequent numbers are 50 (18 times), 28 (17 times), 13, 22 (14 times), 30 (12 times), 84 (11 times), and 14, 393 (10 times). The unbroken code of Catinat (7) appears to be different from this in view of these characteristics. Moreover, numbers 28 and 50 occur only once in the undecoded message of (7). None of the known codes above can solve this, either. The most frequent two-group sequences are: "41 269" (5 times), "13 101", "50 84" (4 times), "50 28", "82 30", "101 22", "183 284", "269 17", "284 13" (3 times each). Of these, all instances of "269" are in the sequence "41 269". The successive occurrences of two-digit numbers may suggest the code is something similar to the one described in (4) above, rather than a purely two-part code as broken by Bazeries. This hypothesis may be supported by the fact that no less than 253 groups out of 591 are lower than 100. (See statistics: (0) frequency, (1) frequency (descending order), (2) two-group frequency, (3) two-group frequency sorted by the second group, (4) preliminary contact analysis, (5) contact chart, (6) frequency histogram in comparison to (8B) above.)

The letter appears to be addressed to Beat Jakob II Zurlauben (Schmeh; Büsser (2008)). (Another Beat Jakob Zurlauben was lieutenant general in the service of France and the owner of the regiment Zurlauben (Wikipedia in German). In 1702, Lieutenant General Zurlauben was in Italy (Vault, p.725, 192, 231, etc.) and the regiment served in Flanders (ibid., p.482, 579, etc.).)

The letter is written at the camp of "Inglesheim", a name not found in today's map. Several possibilities are discussed in the blog, of which one is Ingenheim, which is tolerably consistent with the historical background below.

The letter was written in the last period of Catinat's active career.

Historical Background

Nocolas Catinat was made a marshal of France in 1693 during the War of the Grand Alliance. When the War of the Spanish Succession broke out in 1701, he was in command in North Italy but was transferred to Alsace in September 1701 (Frey, p.86, 479) and established a camp near Metz (Sturgill, p.18, 19).

In 1702, it was proposed that the French should cross the Rhine at Hüningen (now Huningue in France, near Basel) and make a junction with the Bavarian forces, the new ally of the French. Duc de Villars considered the combined forces should march on the right bank of the Danube in cooperation with the army in the Italian front but was frustrated by the cautious attitude of Catinat. (Vault, p.20-21)

In the meantime, Catinat had taken a position near Ingenheim (near Strassburg, between Saverne and Haguenau) on 17 August (Vault, p.363, 824) and decamped on 30 August (p.366). He attempted at a diversion in favor of Landau under a long siege by marching down the Rhine via Drusenheim to Roeschwoog (p.366, 370) but, when informed that Landau was taken on 9 September by the Imperial forces under the Margrave of Baden, he decamped on 11 September (p.372) and withdrew to a camp near Strassburg on 14 September, with the right near Schiltigheim (a few kilometers north of Strassburg) and the left at Eckbolsheim (p.373).

Almost at the same time as the fall of Landau, the Elector of Bavaria showed his hand and took Ulm by surprise (Churchill, p.637). But the communication between Bavaria and the French was made difficult by the vigilance of the Imperialists (Vault, p.374). (As an example, the Imperial minister in Switzerland armed his servants to catch messengers and couriers (Churchill, p.637-638, Vault, p.839, Sturgill, p.21).) In a despatch to the King on 14 September, Catinat could only report the seizure of Ulm by information of merchants (Vault, p.379). At this time, Beat Jakob II Zurlauben in Zug, Switzerland, was an intermediary for handling correspondence between the French ambassador in Solothurn, Switzerland, and Ricours or Ricous, French minister to the Elector of Bavaria, through hostile territories (Büsser, p.75).

Learning the fall of Laudau, the Elector was concerned with the security of his own territory and countermanded the march of a detachment to join with the French. However, his messenger to Catinat to inform of this change of plan was captured (Sturgill, p.20-21, cf. Churchill p.637-638). It was only on 20 or 22 September that an officer arrived at Catinat's camp and informed him of the Elector's order that his detachment should go no further than Stühlingen (Vault, p.374-375; Sturgill p.22). Worse still, although Catinat used cipher in his letters, the Elector did not and the intercepts revealed his plans to the allies (Vault, p.374).

Finally, Villars was given command of forces to cross the Rhine and won a victory at Friedlingen (near Basel) on 14 October against the Imperial forces under the Margrave that marched up the Rhine. Although the French and Bavarian forces could not yet effect a junction, this opened a path between the Elector on the Danube and the French on the Rhine (Lynn, p.276).

(By the way, the day before, Villars reported wasting seven hours with his secretary in trying in vain to decipher a letter he received from Ricous, which employed a small cipher different from the cipher between the Elector and Catinat, of which Villars had a copy (Vault, p.404, 414, 839, 841-842, 858; the note on p.841 says the latter part of the letter in the archives (Archives du dépôt de la guerre, original, vol.1582, no.97) is not deciphered).)

Catinat soon resigned for retirement (Frey, loc. cit.).

References for this Section

Klaus Schmeh, Wer knackt diesen verschlüsselten Brief von Nicolas de Catinat?, 1 May 2016, Klausis Krypto Kolumne (blog entry) ... images are available

Bernard (ed.) (1819), Mémoires et correspondance du Marechal de Catinat de la Fauconnerie, Tome III, Livre X (Google) This prints a letter from the Elector on 23 September 1702 on p.174.

Vault (ed.) (1836), Mémoires militaires relatifs à la succession d'Espagne sous Louis XIV, Tome II (Google)

Nathalie Büsser (2008), "Salpeter, Kupfer, Spitzeldienste und Stimmenkauf: die kriegswirtschaftlichen Tätigkeiten des Zuger Militärunternehmers und Magistraten Beat Jakob II. Zurlauben um 1700 für Frankreich", Schweizerische Gesellschaft für Wirtschafts- und Sozialgeschichte (pdf) ... see esp. p.75 and note 32

Linda Frey and Marsha Frey (ed.), The Treaties of the War of the Spanish Succession, An Historical and Critical Dictionary

Claude Sturgill, Marshal Villars

John A. Lynn, The Wars of Louis XIV 1667-1714

Winston Churchil, Life and Times (2 vols.), Book One, George G. Harrap & Co. Ltd. (London, 1947 ed.)

ViaMichelin ... Searchable map

(10) Code between Guelders and Rheinberg (November 1702)

(DE=21/87/135) Lambeth Palace Library preserves a French coded letter of 20 November 1702 deciphered by the British (MS 930, no.5, no.6). Addressed to Monsieur de Rogon, at Guelders, from Rheinberg, 20 November 1702, it conveyed instructions to a commander of dragoons.

Unlike the codes used by the King in April (see above), it employed two-part principles (i.e., random arrangement of entries). However, it had less than 400 entries (up to at least 383) and even the word "ennemi" had to be spelled as "190(en)-232(ne)-156(mi)" (twice). The British decipherer succeeded in reading it for the most part.

Historical Background

At the beginning of the War of the Spanish Succession, the French held all the major towns along the Meuse and the lower Rhine (with an important exception of Maastricht) and even the Dutch city of Nimwegen was threatened. However, the Duke of Marlborough commanding the allied forces completely turned the table. In September, shortly after the news of the capture of Landau from the French reached, Venloo fell. Roermond, Stevensweert, and, further up the Meuse from Maastricht, Liège were captured by the end of October. On the Rhine, Kaiserswerth had been captured from the French in June and Marlborough arranged for a winter siege of Rheinberg. Now, the control of the Meuse and the lower Rhine was in the allies' hand but the town of Guelders, fortified and protected by marshes, between the rivers was still held by the French (Churchill, p.606).

As of early November 1702, the allies went into winter quarters except for those besieging Rheinberg, which fell in February 1703 (Churchill, p.605, 604).

(11) Code related to the War of the Spanish Succession (ca.1702-1704)

(DE=4u) Another cipher is found in BnF Clair. 452 (f.200), which is a collection of documents from 1702-1710.

Unlike other ciphers at the time, this is not an ordinary numerical cipher. It employs numbers up to 100 (not 99), and other letter-letter or figure-letter combinations for letters, syllables, words, word elements, and names.

The nomenclature begins with names related to the Spanish court (Princess of Ursins, Cardinal Portocarrero, etc.). The entry "La Reyne d'Angleterre" indicates this belongs to Queen Anne's reign (1702-1714). French generals (Villars, Villeroy, Bouflers, Tallard) in the War of the Spanish Succession are listed. This must have been made before the Battle of Blenheim (1704), after which Tallard was a prisoner in England. The entry "le roy des romains" indicates that this was before Joseph became Emperor in 1705, after which the King of Romans was vacant for some decades.

Louvois' Ciphers Preserved in BnF fr.6204

I learned of BnF fr.6204 (Gallica) in Biermann (2020) (DOI) quoted above. The volume, titled "Recueil de chiffres diplomatiques (1688-1713)", contains dozen ciphers. Some are annotated as Louvois'. The others may also belong to the War Minister, given that all share the characteristics of Louvois' ciphers. That is, letters/syllables/names are mixed in random arrangement.

In these ciphers (at least in all of the enciphering tables), the alphabet includes "K".

no.1, no.2 (DE=68/229/242) "Chiffre commun entre M. de Louvois et M. de Maumort et M. le comte d'Avaux" (1688)

(f.1-2 for deciphering; f.3-4 for enciphering) Eelements up to 628.

Many numbers are defined as cancelling symbols: "annulantes cest a dire qui rendent nul le nombre qui les suit" and "annulanes cest a dire qui rendent nul le nombre qui les precede."

no.3, no.12 (DE=13/46/219) "Chiffre commun entre M. de Louvois et M. Tirconel" [ca.1688-1691]

(f.5-6 for enciphering; f.23-24 for deciphering) Elements up to 547 (excluding blank entries up to 625). The section "noms propres" includes Waterfort (346), Kinsale (114), Lymmerick (3), etc. (Tyrconnell, Lord Deputy of Ireland, supported the deposed Jamaes II after the Glorious Revolution, but died of a stroke in August 1691.)

There are "nulles" as well as "annulantes qui rendent nul le nombre suivant."

no.7 (DE=143/205/297) "Chiffre commun entre M. de Lauzun, M. de Louvois et M. le Premier"

(f.13-14) Elements up to 451. This is the cipher used in 1690 that John Wallis could not break (see above).

There are "nulles" as well as "annulantes cest a dire qui rendent nul le nombre suivant."

The ciphers from 1696 and 1701 presented below all have a similar format with a double frameline.

no.4 (DE=37...) "Chiffre avec M. d'Usson" (14 September 1701)

(f.7-8 "a Dechiffrer") Elements up to 830 (excluding blank entries up to 1000). The random arrangement mixing letters, syllables, and words is in contrast with the alphabetical arrangement in the cipher used in a letter from Louis XIV to M. d'Usson (see above). That is, Louvois used a stronger code than the King.

Some names are erased: "l'Esl[ecteu]r de Mayenne" (153), "M. le Maral de Boufflers" (177), "Le Duc d'hannovre" (212), "l'Evesque de Munster" (256), "l'Eslr de Treves" (267), "le Pce Eugene" (309), "l'Eslr de Baviere" (323), "M. le Maral de Catinat" (336), "Dannemarck, Dannois" (350), "le Duc Antoine[-Ulrich?]" (398), "M. le marg. d'Usson" (411), "le Duc de Wolfenbutel" (444), "l'Eslr Palatin" (477), "Eslr de Cologne" (618), "le Roy de Pologne" (650), "Suede, Suedois" (657), "l'Eslr de Brandenbourg" (701), "les ministres de la cour de vienne" (711), "le Duc de Zell" (720), etc.

no.5 (DE=597/811/783) "Chiffre avec MM. les maréchaux de Tallard et de Marcin"

(f.9-10 "Pour Chiffrer") Elements up to at least 886 (M. de Ricous).

The alphabet includes "&", "ns", "nt", "rs", "st."

There are "nulles" as well as "annullent le nombre precedent" and "annullent le nombre suivant."

no.6 (DE=250...) "Chiffre avec M. Bouchu" (3 December 1701)

(f.11-12 "a Dechiffrer") Elements up to 820 (excluding blank entries up to 1000).

no.8 (DE=104/617/766) "Chiffre avec M. le maréchal de Villeroy" (1 June 1701)

(f.15-16 "a Chiffrer") Elements up to at least 843 (null).

The alphabet includes "&", "ns", "nt", "rs", "st."

There are "nulles" (but not cancelling symbols).

no.9 (DE=31/290...) "Chiffre avec M. le maréchal de Boufflers" (19 January 1701)

(f.17-18 "Table a Dechiffrer") Elements up to 834 (excluding blank entries up to 1000).

no.15 (DE=34...) "Chiffre avec M. le duc de Vendosme" (1 May 1696)

(f.29-30 "a Dechiffrer") Elements up to 813 (excluding blank entries up to 1000).

no.16 (DE=400/411/423) "Sixieme Clef a Chiffrer"

(f.31-32) Elements up to at least 711 (ue). Numbers 720-999 are nulls.

The alphabet includes "&", "ns", "nt", "rs", "st."

no.13, no.14 (DE=78/161/346) "Chiffre remis par M. de St-Maurice" (22 June 1713; made in March 1711)

(f.25-26 "Pour Chiffrer"; f.27-28 "Pour Dechiffrer") Elements up to 495.

The alphabet includes "&."

There are "nulles" (but not cancelling symbols).

no.10, no.11 (DE=48/210/568) anonymous cipher

(f.19-20 for enciphering; f.21-22 for deciphering) Elements up to 927.

The alphabet includes "&."

There are "nulles" as well as "annullent le nombre precedent" and "annullent le nombre suivant."

Observations on Codes/Ciphers during the Reign of Louis XIV

Numerical cipher without use of arbitrary symbols appears to have become the standard in France in the early 17th century (see another article). Thus, the codes/ciphers during the reign of Louis XIV used 300 to about 900 numbers to represent letters, syllables, and frequently used words and names.

Three diplomatic codes from 1661, 1675, and 1676 use two-digit figures with diacritics (see another article), the practice not seen in later ciphers known to me.

The 17th century saw introduction of two-part code, whereby entries are not arranged alphabetically and thus separate tables are provided for encoding and decoding. It is often said to have been devised by Antoine Rossignol (1600-1682), who served Louis XIII as well as Louis XIV as a codebreaker. He must have known from his own experience that codebreaking would be made more difficult by irregular arrangement of entries.

However, the non-alphabetical arrangement was not always fully implemented. For example, the above ciphers of (2) 1689 and (4) 1690-1693 had single letters in alphabetical order in low numbers. Moreover, the arrangement of syllables and words was not completely random but those with the same initial letter tended to follow one another with an interval of ten. Probably, the original cipher was arranged on a sheet as in the images shown above, which allows the single sheet to serve for both encoding and decoding purposes. (So, technically, it is a "one part" code.) The regularity allowed John Wallis, an English mathematician, who deciphered many French ciphers during the English Civil War as well as after the Glorious Revolution, to guess that, for example, a certain code number indicated a name beginning with a D.

On the other hand, as early as (1) 1676, Louvois had a cipher that appears to adopt a completely random arrangement of not only words but also single letters, both mixed together. Indeed, Wallis could not decipher Louvois' dispatches of (5) 1690, which is probably based on such a random arrangement, and others of (6) 1691 were only broken at the end of the 19th century.

In addition to common techniques such as homophonic substitution (having more than one symbol) and nulls (insignificant symbols), Wallis' deciphering of the (2) 1689 cipher and (3) another cipher shows that the French also used a symbol to delete a preceding symbol and another symbol used in a pair to delete everything in-between.

Use of a symbol to represent several variants (as in those of (2) 1689 and (8) 1690) is a feature that would be also seen in French ciphers in the Napoleonic age. While there should be a line placed below a figure for disambiguation, these were occasionally neglected, according to Wallis.

Wallis observed in 1689 the French "change their cyphers so often, and study every time to make them harder than before". In 1697, he said in his autobiography "of late years, the French Methods of Cipher are grown so intricate beyond what it was wont to be, that I have failed of many; tho' I have master'd divers of them." (see another article) Notwithstanding his testimony, later ciphers were not necessarily better than previous ones, as noted above.

Why did Louis XIV use a weaker one-part code as late as (8B) 1702 and (4) 1690/1693, when a securer two-part code was known at least as early as (1) 1676. I was made aware of an explanation by comments by Norbert Biermann in Klausis Krypto Kolumne. The two-part codes of (1) 1676, (6) 1691 (the one broken by Bazerie), and possibly (5) 1690 concern Louvois (Wikipedia), Minister of War in 1662-1691. On the other hand, one part codes such as (2) 1689, (4) 1690 were used by diplomats, presumably under Colbert de Croissy, Foreign Secretary (Wikipedia). Rivalry between the ministers may have prevented the principle of two-part code from being shared with ambassadors.

Codes/ciphers tend to be preserved by those who broke them. Inspection of John Wallis' papers would be desirable to obtain further insights on French ciphers during this period.

Related Articles:

S. Tomokiyo, "French Ciphers during the Reign of Louis XIII"

S. Tomokiyo, "Ciphers Early in the Reign of Louis XIV"

S. Tomokiyo, "French Ciphers at the time of the Fronde"

©2015 S.Tomokiyo
First posted on 26 March 2015. Section (9) added in May 2016. Sections (8B)(10) added in June 2016. Section (8A) added in August 2018. Section (1B) added in September 2018. Section (4B) added in February 2019. Section (11) added in September 2020. Section (12) added in February 2021. Last modified on 15 October 2021.
Cryptiana: Articles on Historical Cryptography
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