Following the outbreak of World War One, Jack volunteered for service and joined the 6th Battalion King’s Own (Royal Lancaster). He saw active service as a signaller in the Middle East. In March 1917, while advancing on Baghdad, Jack bravely saved the life of the other men in his pontoon and prevented vital equipment from falling into enemy hands. Three months later, due to his actions, the King awarded Jack the Victoria Cross. He was decorated in April 1919.