Secrets of the Foreign Policy of the Last Valois in Northern Europe: The Diplomatic Cipher of Charles de Danzay

In the study of the foreign policy strategies of Renaissance royal courts and the activities of their diplomatic agents, the analysis of ambassadorial correspondence – imbued with various codes, symbols, and cryptographic practices – occupies an important place. This article presents, for the first time, a reconstruction of the diplomatic cipher used by Charles de Danzay, representative of the French royal court in Denmark between 1548 and 1589. An analysis of two of his letters – dated 14 October 1574, and 28 February 1578 – has made it possible to reconstruct the cipher table published in the appendix to the article. This table represents a classic French Renaissance cipher based on a homophonic system. These letters hold a special place in the context of Baltic history and the foreign policy of the last Valois monarchs. The diplomatic and intelligence network of the Valois, which flourished in northern and northeastern Europe in the second half of the sixteenth century, transformed the French kingdom of the Wars of Religion period into one of the key actors in the region, advancing large-scale geopolitical projects aimed at securing royal thrones in Poland and the Grand Duchy of Lithuania, Sweden, and Livonia. The encrypted information contained in the two letters examined – concerning the escalation of Danish- Swedish tensions following Stockholm’s failure to comply with the terms of the Treaty of Stettin, as well as the English crown’s plans to create a pan-Protestant alliance – was of particular value to the French royal court. The court sought to preserve its influence in the Baltic world by preempting threats that could undermine the authority of the last Valois and create an unfavorable geopolitical situation for them within the European arena. The article also briefly discusses the unencrypted portions of the letters, which concern Franco-Polish negotiations following the flight of Henry de Valois from the Rzeczpospolita, the internecine conflict in the German Duchy of Saxe-Lauenburg, and Franco-Russian trade in the Baltic region. Both letters are published in the appendix to the article.