On returning from his first visit to the USA, Thomas Mann found “a beautiful old book” waiting for him in Küsnacht, his Swiss refuge outside Zurich. It bore the title Johann Müller's Briefe an seinen ältesten Freund in der Schweiz (Johann Müller's Letters to His Oldest Friend in Switzerland) and contained the dedication: “Thomas Mann / mit guten Wünschen herzlich gedenkend / zum 6. Juni 1934 / Köln Ernst Bertram” (To Thomas Mann / with good wishes and cordially thinking of him / for the 6th June 1934 / Cologne Ernst Bertram).

Müller was a historian and a contemporary of Goethe. Some of the letters, which had been published posthumously from his literary remains, testify to the high regard Müller had for Frederick II and his “most glorious deeds.” Müller (1752–1809) had quoted four lines of verse from one of Frederick's letters, together with some words of Christ admired by the monarch:

Mann marked the first sentence of this homage to the king with an “x.” Lines of verse and the quotation from the Bible reminded the exile of a time in his own past. Thirty years earlier he had planned to write a “historical novel with the title of ‘Friedrich,’” because at the time he had regarded the king of Prussia as a “great” man and king. In 1739, while still crown prince, Frederick had defined his future office in his Antimachiavell (1740) in this manner: “The sovereign is under no circumstances an absolute ruler of his people who are under his yoke; he is instead no more than the highest of the civil servants.”