German military balloon corps. German soldiers with carts containing cylinders of hydrogen gas and an deflated balloon (on ground). This photograph dates from the period between 1910 and 1915. Observation balloons were used by both sides during World War I (1914-1918) to direct artillery fire and survey enemy positions. The German balloon corps were part of the Imperial German Army (the Deutsches Heer). This photograph is from the Bain News Service, one of the USA's earliest news picture libraries.