Which First World War battle did J.R.R. Tolkien serve in as a British Army officer?

J.R.R. Tolkien served in the Battle of the Somme during the First World War.

Tolkien was commissioned as a second lieutenant in the Lancashire Fusiliers and arrived on the Western Front in 1916. He took part in the Somme offensive, one of the largest and bloodiest campaigns of the war. After several months, he became ill with trench fever and was sent back to England for treatment.

Tolkien lost several close friends during the war, including members of the informal group he called the Tea Club and Barrovian Society. These experiences profoundly affected him, although it is too simplistic to claim that particular characters or events in Middle-earth directly correspond one-for-one with the Somme.

The Battle of the Somme began on 1 July 1916 and continued until November. Tolkien’s military service and illness interrupted his early career, but he continued writing and developing stories during and after the war.