What was the name of the World War I battalion where Tolkien served as a signals officer?

J.R.R. Tolkien served as a signals officer with the 11th Lancashire Fusiliers during World War I.

Tolkien joined the 11th Battalion, Lancashire Fusiliers, and trained in signaling before being sent to France in 1916. His duties involved military communications, a dangerous responsibility on the Western Front. The battalion took part in fighting during the Battle of the Somme, including the assault on the Schwaben Redoubt.

Biographical accounts often simplify this by saying that Tolkien served in the Lancashire Fusiliers, which is correct but less precise. The 11th Battalion identifies the specific unit. Tolkien’s later illness ended his active service, and he spent much of the rest of the war recovering and performing duties in England.