The article, based on unpublished materials from the Archive of Foreign Policy of the Russian Empire, reconstructs the details of the stay in St. Petersburg and Moscow of Minister Plenipotentiary of the Holy Roman Emperor Charles VII Baron Joseph Maria von Neuhaus, who came to prevent Empress Elizabeth Petrovna from entering the War of the Austrian Succession on the side of Austria. Neuhaus’ mission was accompanied by a number of difficulties, the main one was to obtain permission from the Russian court to present his credentials. The absence of Elizabeth Petrovna’s imperial title in the letter of credence deprived Neuhaus of the opportunity to be accredited at the Russian court for a year and four months, and consequently of his public status, that made any negotiations impossible. The article also analyses the organizational and financial problems of diplomatic and courier service in wartime, and the peculiarities of etiquette formulas in official correspondence between Russia and the Holy Roman Empire.