709.587.300.46.250.741.255.38.545.19 …
si la [guerre] avec l’[Angleterre] avoit lieu il seroit …

Martinique → Versailles · Bouillé’s numerical nomenclator of 1778 · 2 Nov 1787 · read with known key

Damas to the minister of the Navy, 1787

A governor’s plan for war with Britain, enciphered in a cipher nine years old, whose margin names it and which the key of Bouillé’s letters reads unchanged.

Daniel Bourdeau · posted

Method: read with known key · Extent: complete

Contributed by Brice Dudout (solution)

At a glanceKnown key applied · complete

The letter
The comte de Damas, governor general of the Windward Islands, to the Secretary of State for the Navy, 2 November 1787 (no. 501), a signed original that sends news from the British islands.
Where
Archives nationales d’outre-mer, COL C8 B 16, no. 61 (images FRANOM23_C8B_16_0260–0261). The inventory says “Nouvelles des îles anglaises (chiffrée)”.
The cipher
The margin reads “Chiffre du 25 avril 1778”: Bouillé’s numerical nomenclator of 1778–1782, still in use nine years later. It has its own page.
How it was deciphered
Key K6, rebuilt from Bouillé’s glossed letters and frozen, was first checked on this letter: it covers 92% of the groups, the most frequent numbers (361, 817, 607, 250) are Bouillé’s, and “M. le comte de Grasse” is enciphered as in 1779. It read a held-out letter against its modern translation at 0.894 of words, against at most 0.182 for 200 permuted keys.
What it says
If war came, Damas would seize Dominica. He lacks siege and field artillery, orders and money, and he gives the garrisons of the islands.
Still open
Four groups are unresolved (269, 464, 686, 190). The images were not seen here.
Credit
Brice Dudout checked the cipher, applied the key and read the letter, working with Claude Opus 5.5 agents.

01 The letter

In September and October 1787 the Prussian intervention in Holland, backed by Britain, raised fears of an Anglo-French war. Damas sends news from Dominica in clear, then switches to cipher to say what he would do if war came and what he lacks. He does not yet know that France backed down at the end of October. He plans the defence of the islands France held after 1783 (Saint Lucia and Tobago) and thinks of retaking Dominica, which went back to Britain at the peace of 1783 after Bouillé had taken it in 1778. The artillery he lacks had left with de Grasse’s squadron in 1781–82.

02 The cipher and the key

The key is K6 of the Bouillé 1778 page: 490 values from the pencil glosses of seven letters of 1779–80, frozen before any validation. Before reading, the identity of the cipher was checked, and the numbers decipher consistently with it. We re-applied K6 to the transcription on 2 November 2026: 445 of 465 numbers agree with the decryption file and 6 are not in the key; the rest are marked alternates and unresolved groups.

03 The reading

Of the 302 words of the cipher part (463 numbers), 298 are read as sense (98.7%): 281 certain, 5 probable and 12 restored. Every probable or restored word is justified in the notes. For example, 300 is restored as guerre in “si la guerre avec l’Angleterre avoit lieu” because the same phrase recurs below with the glossed 710 for guerre. The full French reading and an English translation are under Full texts.

04 What remains uncertain

Full texts

The transcription and the decryption of every document on this page, so that the reading can be used and checked. Short files are shown here; all are in the repository.

Damas to the minister of the Navy, Martinique, 2 Nov 1787 (cipher part)

If war with England came, Dominica should be seized; Damas lacks siege and field artillery, orders and funds; garrisons of the Windward Islands.

Transcription

transcription.txt

# ANOM COL C8 B 16 no. 61, Damas to the minister, Martinique 2 Nov 1787 (IREL images FRANOM23_C8B_16_0260-0261). Image not included.
# https://recherche-anom.culture.gouv.fr/ark:/61561/zn401hbchfcz
# Margin: "Chiffre du 25 avril 1778". "(du 4 août 1786.)" is in clear inside the cipher. "/" = new paragraph.

709.587.300.46.250.741.255.38.545.19.298.305.496.184.1.185.95.
770.361.817.727.503.1.361.138.45.817.718.817.143.1.361.587.243.
135.430.195.102.292.46.428.;266.57.719.705.52,503.607.817.269.
817.56.250.564.350.110.400.270.44.398.634.,798.677.103.371.443.344.587.
549.266.250.404.44.  88.116.339.126.226.788.17.245.110.848.361.102.
135.665.256.266.361.709.162.590.:211.17.393.286.266.763.317.
187.321.305.162.735.607.107.45.250.377.292.361.369,143.250.278.
361.533.607.243.135.398.361.748.817.305.
/ 208.5.398.339.412.607.817.613.56.687.135.255.525.52.491.279.
622.503.680.827 (du 4 août 1786.) 45.250.182.669.807.245.381.486.
815.361.583.817.44.799.345.292.252.817.,762.45.607.817.241.90.
817.718.705.135.734.632.56.45.270.103.91.246.116.339.585.770,
266.279.24.17.245.88.339.251.321.705.352.808.613.143.270.44.398.
503.754.17.184.1.185.95.339.398,520.57.718.525.52.705.412.545.
361.750.607.817.478.817.361.250.848.636.709.135.627.146.754.23.
361.118.
/ 709.587.710.143.605,298.187.252.56.57.147.17.52.777.207.718.590.
110.848.361.709.17.590.266.777.361.102.135.665.256.88.339.251.317.
56.381.508.17.622.412.102.285.651.361.67.81.412.739.195.1.85.298.
737.23.464.777.182.669.807.245.361.686.266.361.189.607.50.255.
250.190.361.587.216.
/ 607.817.634.361.752.266.831.522.431.150.102.292.23.5.398.339.
620.798.443.251.44.644.718.332.482.775.817.819.226.576.185.,284.
305.754.23.621.770.143.587.631.709.525.451.328.75.777.243.103.358
361.128.244.88.772.23.645.103.666.195.509.607.817.663.23.444.244.848.
/ 428.718.381.663.110.777.740.355.17.705.709.817.417.339.270.95.268.244
393.361.267.246.522.636.195.525.636.718.250.848.328.,807.173.107.
645.103.666.195.666.636.448.56.479.545.453.37.493.17.735.607.817.
271.817.;393.361.752.641.453.81.770.17.,244.393.361.831.453.67.81.331.
339.776.44;451.781.381.116.587.381.38.12.587.775.187.676.694.
Decryption

decryption.txt

# Group-by-group decryption with the frozen key K6 of targets/bouille1778 (same cipher). <n> = group absent from the key.

709.587.300.46.250.741.255.38.545.19.298.305.496.184.1.185.95.
si la <300> avec l' <741> à vo it lieu il se roit int er es sa

770.361.817.727.503.1.361.138.45.817.718.817.143.1.361.587.243.
nt de s em par er de la-dominique pour s a s sur er de la co

135.430.195.102.292.46.428.;266.57.719.705.52,503.607.817.269.
m mu ni ca tion avec la-guadeloupe et vous ver re z par le s <269>

817.56.250.564.350.110.400.270.44.398.634.,798.677.103.371.443.344.587.
s que l' on pren d' dans ce t te isles qu'il fa u dra y employé la

549.266.250.404.44.  88.116.339.126.226.788.17.245.110.848.361.102.
force et l' ar t je ma n que ent <788> e ment d' artillerie de ca

135.665.256.266.361.709.162.590.:211.17.393.286.266.763.317.
m pa gne et de si e ge tout e celle qui et oit ici

187.321.305.162.735.607.107.45.250.377.292.361.369,143.250.278.
est pas se e sou le vent pour l' expédi tion de saint sur l' escadre

361.533.607.243.135.398.361.748.817.305.
de m. le co m te de gra s se

/ 208.5.398.339.412.607.817.613.56.687.135.255.525.52.491.279.
<208> at te n du le s ordres que vous m à ve z an non

622.503.680.827 (du 4 août 1786.) 45.250.182.669.807.245.381.486.
ces par votre lettres pour l' ap provision ne ment des bo

815.361.583.817.44.799.345.292.252.817.,762.45.607.817.241.90.
is de con s t ru c tion nécessaire s <762> pour le s af <90>

817.718.705.135.734.632.56.45.270.103.91.246.116.339.585.770,
s a re m pla cer que pour ce u x qui ma n qu' nt

266.279.24.17.245.88.339.251.321.705.352.808.613.143.270.44.398.
et non seul e ment je n ai pas re cu <808> ordres sur ce t te

503.754.17.184.1.185.95.339.398,520.57.718.525.52.705.412.545.
par ti e int er es sa n te mais vous a ve z re du it

361.750.607.817.478.817.361.250.848.636.709.135.627.146.754.23.
de puis le s fond s de l' artillerie au si m ple entre ti en

361.118.
de paix

/ 709.587.710.143.605,298.187.252.56.57.147.17.52.777.207.718.590.
si la guerre sur vient il est nécessaire que vous envoi e z un équip a ge

110.848.361.709.17.590.266.777.361.102.135.665.256.88.339.251.317.
d' artillerie de si e ge et un de ca m pa gne je n ai ici

56.381.508.17.622.412.102.285.651.361.67.81.412.739.195.1.85.298.
que des pi e ces du ca li bre de qua tre du der ni er objet il

737.23.464.777.182.669.807.245.361.686.266.361.189.607.50.255.
faut en ar un ap provision ne ment de <686> et de bou le ts à

250.190.361.587.216.
l' <190> de la marine

/ 607.817.634.361.752.266.831.522.431.150.102.292.23.5.398.339.
le s isles de sainte-lucie et <831> sont sans fortifi ca tion en at te n

620.798.443.251.44.644.718.332.482.775.817.819.226.576.185.,284.
<620> qu'il y ai t <644> a crain dre quel s soit ent attaque es elle

305.754.23.621.770.143.587.631.709.525.451.328.75.777.243.103.358
se ti en dro nt sur la défen si ve à pres venir un co u p

361.128.244.88.772.23.645.103.666.195.509.607.817.663.23.444.244.848.
de main <244> je leur en fo u r ni rai le s moyens en munitions <244> artillerie

/ 428.718.381.663.110.777.740.355.17.705.709.817.417.339.270.95.268.244
la-guadeloupe a des moyens d' un lon gu e re si s ta n ce sa garnison <244>

393.361.267.246.522.636.195.525.636.718.250.848.328.,807.173.107.
celle de la-martinique qui sont au ni ve au a l' artillerie pres ne peu vent

645.103.666.195.666.636.448.56.479.545.453.37.493.17.735.607.817.
fo u r ni r au plus que hu it cent hommes <493> e sou le s

271.817.;393.361.752.641.453.81.770.17.,244.393.361.831.453.67.81.331.
armé s celle de sainte-lucie deux cent tre nt e <244> celle de <831> cent qua tre vi

339.776.44;451.781.381.116.587.381.38.12.587.775.187.676.694.
n g t à cause des ma la des vo i la quel est notre situation
Reading

reading.md

# Established text (French)

## Clear opening

J’ai l’honneur de vous envoyer la copie des nouvelles qui me parviennent de la Dominique. N’ayant reçu aucun avis de vous, j’y ajoute peu de foi ; cependant j’ai expédié sur-le-champ un bâtiment léger pour Sainte-Lucie et Tabago, afin que les gouverneurs se tiennent sur leurs gardes, sans cependant mettre de l’apparat dans leurs précautions. J’ai fait passer la copie de ces nouvelles à la Guadeloupe et j’ai pris des moyens pour être instruit des mouvements qui pourroient avoir lieu à la Barbade et dans les autres isles angloises.

## Cipher part

Si la [guerre] avec l’[Angleterre] avoit lieu, il seroit intéressant de s’emparer de la Dominique pour s’assurer de la communication avec la Guadeloupe, et vous verrez par les ‹269›s que l’on prend dans cette isle qu’il faudra y employer la force et l’art. Je manque {entièrement} d’artillerie de campagne et de siège ; toute celle qui étoit ici est passée sous le Vent pour l’expédition de Saint‹…›, sur l’escadre de M. le comte de Grasse.

{J’ai} attendu les ordres que vous m’avez annoncés par votre lettre ‹clear: du 4 août 1786› pour l’approvisionnement des bois de construction nécessaires, [tant] pour les {affûts} à remplacer que pour ceux qui manquent ; et non seulement je n’ai pas reçu [d’]ordres sur cette partie intéressante, mais vous avez réduit depuis les fonds de l’artillerie au simple entretien de paix.

Si la guerre survient, il est nécessaire que vous envoyiez un équipage d’artillerie de siège et un de campagne ; je n’ai ici que des pièces du calibre de quatre. Du dernier objet il faut en ‹464› un approvisionnement de ‹686› et de boulets à l’‹190› de la marine.

Les isles de Sainte-Lucie et [Tabago] sont sans fortification ; en {attendant} qu’il y ait [lieu] à craindre qu’elles soient attaquées, elles se tiendront sur la défensive, à prévenir un coup de main ; [et] je leur en fournirai les moyens en munitions [et] artillerie.

La Guadeloupe a des moyens d’une longue résistance ; sa garnison [et] celle de la Martinique, qui sont au niveau, à l’artillerie près, ne peuvent fournir au plus que huit cents hommes [chacune] sous les armes ; celle de Sainte-Lucie, deux cent trente, [et] celle de [Tabago], cent quatre-vingts, à cause des malades. Voilà quelle est notre situation.

## State of the reading

First published decipherment, to our knowledge. Published under Daniel Bourdeau’s rule: 95% of the words read in their sense. Cipher part (463 numbers, 302 words): 298 words read in their sense (98.7%), of which 281 certain (93.0%), 5 probable {x} (1.7%) and 12 restored from the sense [x] (4.0%); 4 unresolved ‹…› (1.3%): ‹269›, ‹464›, ‹686›, ‹190›.

## Justifications

- Probable words {x}, with justification. {entièrement}: ent.788.e.ment, 788 = ièr not attested. {J’ai}: 208, not glossed; same number at the head of Bouillé’s letter no. 259 (“208 l’honneur…”), formula “J’ai”. {affûts}: af.90.s; 241 = af is glossed; 90 not attested. {attendant}: at.te.n.620, 620 = dant not attested.

- Words restored [x], with justification. [guerre]: 300 (“si la 300 avec l’741 avoit lieu”); 710 = guerre is glossed, 300 would be a homophone; the same phrase recurs below with 710 (“si la guerre survient”). [Angleterre]: 741, the only possible country in 1787 against the “isles angloises”. [tant]: 762, forced by “… que pour ceux qui manquent”. [d’]: 808 (“je n’ai pas reçu 808 ordres”). [lieu]: 644 (“qu’il y ait 644 à craindre”). [et] (×4): 244, always between two coordinated terms (“munitions 244 artillerie”, “sa garnison 244 celle de la Martinique”, “deux cent trente 244 celle de…”). [chacune]: 493.e (“huit cents hommes 493.e sous les armes”). [Tabago] (×2): 831, paired with St Lucia as in the clear part (“Sainte-Lucie et Tabago”).

- Unresolved. ‹269›s (“vous verrez par les 269.s que l’on prend dans cette isle”: “measures”, “dispositions”?); ‹464› (“il faut en 464 un approvisionnement”; 464 = “ar” in a 1779 gloss, which gives no sense here); ‹686› (“un approvisionnement de 686 et de boulets”: powder?); ‹190› (“à l’190 de la marine”: arsenal?).
Translation

translation.md

# English translation (cipher part)

If war with England were to break out, it would be worth seizing Dominica to secure communication with Guadeloupe; you will see from the […] being taken on that island that force and skill will be needed there. I am entirely without field and siege artillery: all that was here went to leeward for the expedition of Saint-[…], with the comte de Grasse’s squadron.

I have waited for the orders you announced in your letter of 4 August 1786 for the supply of timber, both for the gun carriages to be replaced and for those that are missing; not only have I received no orders on this important matter, but you have since cut the artillery funds to bare peacetime upkeep.

If war comes, you must send me a siege train and a field train: I have here only 4-pounders. For this last point, there must be […] a supply of […] and of shot at the […] of the navy.

St Lucia and Tobago have no fortifications; until there is reason to fear an attack, they will stay on the defensive against a surprise attack, and I shall give them the means in ammunition and artillery.

Guadeloupe can hold out for a long time; its garrison and that of Martinique, equal except in artillery, can each put at most 800 men under arms; that of St Lucia 230, and that of Tobago 180, because of the sick. That is our situation.

Key: key.tsv

05 Sources

Working files: targets/damas1787/ in the repository.