5923043 ?The trail of smoke from the burning remnants of an enemy observation balloon?, 1916 (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: ?The trail of smoke from the burning remnants of an enemy observation balloon?, 1916. Stereoscopic photograph, World War One, Western Front (1914-1918), 1916. Observation balloons were used for intelligence gathering and artillery spotting. Observers would be carried in baskets or containers underneath the balloon. Although the balloons were usually heavily defended by anti-aircraft guns and fighter aircraft, they were a primary target as their destruction reduced an enemy?s ability to direct artillery fire. From a collection of 96 stereoscopic photographs in box two of two entitled ?The Great War? including the official series.); by National Army Museum ; out of copyright.