Although he didn't want to partake in the war, he volunteered for service before conscription started in 1916.

He was placed in the North Staffordshire Regiment, but at the beginning wanted to be with a London Regiment instead.

As a socialist he also insisted on becoming a private. In 1917 he became an officer, and wrote to his brother-in-law, Harry Cooper, advising him to become an Officer too to receive better treatment.

Samuel wrote copiously during the war, and kept many of the letters until he died. At one point, after getting caught in the gas attack he referred to the 'futility' of the war. However, when talking with his grandson in his later years, he refuted this point of view. Instead he stated only his pride in his role in the war.

One of the letters he saved is thought to be a letter to his wife, addressed only to 'FK'. It is a letter written in case of his demise, containing instructions and emotional goodbyes.

Before his death, at a much later date than the previous letter anticipated, Samuel burnt the majority of his personal letters to his wife.

When Frances and Samuel met in 1913 she was a pianist. When Samuel was injured by gas in 1917, and one of his lungs permanently damaged, she became his full-time carer.