With the outbreak of the First World War, Jones enlisted into the London Welsh Battalion of the Royal Welch Fusiliers and served on the Western Front from 1915 to 1918 with the 38th (Welsh) Division. His experiences in the trenches were to prove important in his later painting and poetry, especially his involvement in the fighting at Mametz Wood. Jones spent more time on the front line than any other British writer of the war. He was wounded at Mametz Wood, and spent some time recuperating in the Midlands, before returning to the Ypres Salient and participating in the attack on Pilckem Ridge in 1917. The consequences of this long period in the trenches on Jones's health were slow to emerge. There Desmond Chute taught him to engrave in wood. In 1923 he first worked as an illustrator, for "The Game" published by Gill and H. Pepler. He returned to London in 1924, but in 1925 often visited Gill at Capel-y-ffin and the Benedictines at Caldey Island, near Tenby, and in the same year did illustrations for "Gulliver's Travels" for the Golden Cockerel Press.