J.R.R. Tolkien began writing The Fall of Gondolin in 1917.
He started the story while recovering from illness during the First World War. It tells of Gondolin, a hidden Elven city in the First Age of Tolkien’s mythology, and its destruction by the forces of Morgoth. The tale became one of the foundational narratives of the legendarium that later developed into The Silmarillion.
The story was written before The Hobbit and decades before The Lord of the Rings. Tolkien revised it several times, so later versions differ in detail and emphasis from the earliest manuscript. The setting, characters, and broad catastrophe remained important throughout his evolving mythology.
Christopher Tolkien edited a standalone volume, The Fall of Gondolin, published in 2018. It presents several versions of the tale with editorial commentary, allowing readers to see how Tolkien’s conception changed. The 1917 date refers to the beginning of the composition, not the later publication.