After months in and out of the trenches, Tolkien succumbed to "trench fever" and was sent back to England in November. He spent the next month in hospital in Birmingham and by Christmas he had recovered.

During the war many of his  friends of the “Tea Club, Barrovian Society” had been killed in action. As an act to remember them but also to react against the war experiences, he had begun to write his stories.  This ordering of his imagination developed into the Book of Lost Tales, in which most of the major stories of the Silmarillion appear in their first form: tales of the Elves and the “Gnomes”, with their languages Qenya and Goldogrin, the first recorded versions of the wars against Morgoth, the siege and fall of Gondolin and Nargothrond, and the tales of Túrin and of Beren and Lúthien.