5922471 An invasion balloon anchored on the beach at Salerno, October 1943 (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: An invasion balloon anchored for repair beside a stack of gas cylinders, Salerno, October 1943. Photograph, World War Two, Italy (1943-1945), 1943. An invasion, or barrage balloon, was a gas filled device tethered with metal cables and used to defend against low-level attack by aircraft. In the foreground are Italian prisoners of war being guarded by two Allied soldiers. After the Italian Armistice in September 1943 many prisoners were employed as labourers on sites such as these. From a collection of 34 photographs relating to different theatres in World War Two, 1940-1944.); by National Army Museum ; out of copyright.