A British Drachen-type kite balloon ascending (Drachen being the German for kite). Hydrogen gas-filled balloons had provided military forces with a static platform from which to observe enemy positions since the 19th century. This tradition continued during the First World War. In conditions of relatively static trench warfare, tethered balloons could be launched just behind the front line to observe enemy activity on the opposite side.
At the outbreak of war the Germans held the lead in balloon technology. Their observation units were equipped with Drachen, an elongated gas-bag featuring a large air-filled fin or stabiliser, whereas the British initially had only old-fashioned spherical balloons that gyrated and jumped about in the wind. During 1915, the British produced a copy of the German Drachen type and reorganised their balloons into wings, each containing several sections. Each section was equipped with powerful winches to raise and lower the balloons, and used their own transport and gas tenders to move along the front. In due course the French refined the kite balloon, as the Caquot. This three-finned version was also copied by the British and the Germans.
Observation balloons were usually operated by specially trained officers who were tasked with identifying enemy positions from their lofty perch and range their own artillery upon them. Unlike aeroplane crews, they carried parachutes. Though protected by anti-aircraft guns, balloons were vulnerable to air attack. Some pilots specialised in attacking and destroying balloons. The Belgian ace Willy Coppens downed 34 German observation balloons in six months in 1918. This was highly dangerous work; incendiary ammunition sometimes caused a hydrogen-filled balloon to explode in a ball of flame that could envelope an attacking aircraft.
Operating close to the front, balloon sections were also vulnerable to enemy shelling; New Zealand balloon observer Carrel Fidler was killed by shellfire in Belgium on 19 May 1917.