Which war did J.R.R. Tolkien serve in as a British Army officer?

J.R.R. Tolkien served in World War I as a British Army officer.

Tolkien served as a second lieutenant in the Lancashire Fusiliers. He went to France in 1916 and took part in the Battle of the Somme, one of the First World War’s most devastating campaigns.

He later contracted trench fever and was sent back to England for treatment. Most of the other officers in his battalion were eventually killed, an experience that deeply affected him and informed the emotional background of his later writing.

Tolkien did not serve as a combat officer in World War II. During that conflict he contributed to the war effort in other ways, including serving as an air-raid warden and teaching naval personnel a cryptographic course. His wartime experiences are relevant context, but Tolkien rejected simple one-to-one readings of Middle-earth as an allegory of either world war.