In May 1917, Ackerley led an attack in the Arras region where he was wounded, this time in the buttock and thigh. While he was waiting for help, the Germans arrived and took him prisoner. As an officer, he was assigned to an internment camp in neutral Switzerland, which was relatively comfortable. Here he began his play, "The Prisoners of War," which expresses the cabin fever of captivity and his frustrated longings for another English prisoner. Ackerley was not repatriated to England until after the war ended. Temporary Captain Ackerley relinquished his commission on completion of service, 24 April 1919.