He was a soldier who participated in the war

Lewis enrolled at University College in Oxford during the summer term of 1917, and soon after, he joined the university's Officers' Training Corps, which he described as his "most promising way into the army." After that, he was enlisted for training in a cadet battalion, which is one of the interesting facts about C.S.Lewis. After completing his training, he was commissioned as a Second Lieutenant into the Somerset Light Infantry's 3rd Battalion of the British Army. He was then transferred to the regiment's 1st Battalion, which was then serving in France (he would not remain with the 3rd Battalion as it moved to Northern Ireland). He was sent to France by the British Army to serve in the First World War just months after joining Oxford.

Lewis landed on the front line in the Somme Valley in France on his 19th birthday (29 November 1917), when he first saw trench warfare. Lewis was injured and two of his comrades were killed by a British shell that missed its mark on April 15, 1918, while the 1st Battalion, Somerset Light Infantry attacked the town of Riez du Vintage during the German spring offensive. During his recuperation, he struggled with depression and homesickness, and when he was discharged in October, he was given a job assignment in Andover, England. After being demobilized in December 1918, he immediately resumed his studies. In a subsequent letter, Lewis claimed that his atheism and pessimism were caused by his exposure to the horrors of war, the death of his mother, and his misery at school.