Who received the letters collected in Letters to a Young Poet?

The letters collected in Letters to a Young Poet (Briefe an einen jungen Dichter) were written by the Austrian-German poet Rainer Maria Rilke to Franz Xaver Kappus.1

Kappus was a young military cadet and aspiring poet who corresponded with Rilke between 1903 and 1908. These letters, which offer profound guidance on creativity, solitude, and the human experience, have become one of Rilke's most celebrated works. While Rilke's letters were published posthumously, the letters written by Kappus to Rilke were not included in any edition of the collection until 2019.1