A German Observation Balloon Ready to Ascend during the First World War

A German observation balloon is shown ready to ascend.  During World War I, all major combatants used observation balloons to observe their enemies’ trench lines and troop movements. Observers provided real-time information through telephone and telegraph wiring. They were so effective that early air forces made enemy balloons a target priority. In turn, they were heavily defended by rings of anti-aircraft guns.