What was C.S. Lewis's wartime military unit during World War I?

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

Lewis volunteered for military service while studying at Oxford and was commissioned into the 3rd Battalion, Somerset Light Infantry. He trained for the Western Front and arrived in France in November 1917 as a second lieutenant. His wartime service gave him direct experience of trench warfare and the dangers faced by infantry officers.

Lewis was wounded at the Battle of Arras in April 1918 by fragments from a British shell. His close friend Paddy Moore was killed in the same period, and the loss affected Lewis deeply. Lewis left the army after the war and returned to Oxford, where he completed his studies. The Somerset Light Infantry is sometimes confused with other British or Irish regiments of the period, but it was the unit named in Lewis's commission and military records.