LOUIS XIII (1601-1643), King of France. Autograph letter signed to the Maréchal de Brèze, Noisy, 7 December 1636, one page, small 4to, separate autograph address leaf ('A Mon Cousin le Mar[ech]al de Breze'), small red wax seals, remains of silk cords, docketed by the recipient.
A letter presumably containing secret instructions, written in a code based on a secret language. A postscript written en clair acknowledges receipt of a letter of the 5th of the month, delivered by Monsieur de Chavigny's courier: 'Mon Cousin, zest pernal flaih hagart her rubi citronne racleté, agoelle vitre sol nia soin lili ser a branchér fon a saugrér croche a go tour go dignera blereau vol manlans et tacher adroitement her abonnér saugrer hers harpes tour broderont et faucheront hers solines tour ne me raquettent tor, seron pencer her lily se ... '.
The letter is dated during the war with Spain in which, on 10 November 1636, the recapture of Corbie consolidated French control of the border of Picardy. The exposure of the conspiracy against Richelieu, organised by the King's brother, Gaston, Duc d'Orléans, and the Comte de Soissons, led to the conspirators fleeing Paris on 20 November, and the present letter may be related to these events. Urbain de Maille, Maréchal de Brèze, was ambassador in Holland and Léon de Bouthillier, Comte de Chavigny, the Secretary of State.
By the 16th century, the use of codes had become important for communications on diplomatic matters, and they varied from simple monoalphabetic ciphers (on which the present text may be partly based) to much more complex systems. Louis XIII and his successor employed the talented Rossignol family as cryptologists and by the late 17th century they perfected their 'great cipher', in which groups of numbers were substituted for syllables. (2)