Which branch of the British Army did C.S. Lewis join during World War I?

C.S. Lewis joined the Somerset Light Infantry during World War I.

Lewis served as a second lieutenant in the 3rd Battalion, Somerset Light Infantry. He was commissioned in 1917 and went to France, where he took part in trench warfare during the final stages of the conflict.

In April 1918, Lewis was wounded by shrapnel during the Battle of Arras. His close friend Paddy Moore was killed in the same action. Lewis recovered in England and was discharged from the army in December 1918. The experience left a lasting mark on his writing and contributed to his lifelong awareness of loss and suffering.

Lewis is sometimes associated with Irish military units because he was born in Belfast, but his wartime regiment was the Somerset Light Infantry. His later memoir, Surprised by Joy, discusses his intellectual and spiritual development, although it is not a conventional military memoir.