Two major categories of balloon have been put to military use during the last 200 years. The first, traditional balloons, are pear-shaped, carry a basket suspended underneath, but lack any means of propulsion or guidance. They float with the prevailing wind, or are tethered to the ground. Although many inventors, notably the Montgolfier brothers, had demonstrated the technique, it gained credibility in 1785 when Jean-Pierre Blanchard crossed the English Channel in two hours in a hot-air balloon. Revolutionary France began to experiment with tethered balloons for reconnaissance, for example at the battle of Fleurus in 1794.
In 1849, Austrian troops unleashed unmanned balloons carrying explosives triggered by time fuses against Venice, an experiment discontinued after the vagaries of wind direction made them an embarrassment. During the American civil war, Thadeus Lowe formed a balloon corps for the Union army and directed artillery fire from on high using a telegraph. During the Franco-Prussian war, balloons were used during the siege of Paris, carrying 167 people out of the city and dropping three million psychological warfare leaflets on the Prussian siege lines. At this time, French and German balloonists first exchanged fire, though no hits were recorded. By 1900, all modern armies had established balloon corps to provide timely and accurate battlefield intelligence.
During WW I, all sides used tethered balloons for reconnaissance and artillery spotting, but they remained vulnerable to ground fire and aircraft. WW II saw the development of so-called barrage balloons, which were moored over vulnerable targets, to deny enemy aircraft the ability to make low-level attacks. Barrage balloon cables tore the wings off more than 200 V-1 flying bombs during 1944-5.
The second category of balloon is the airship, or dirigible (Fr.: dirigible, capable of being guided). This possessed a rigid, cigar-shaped frame in which the ‘gasbags’ were stored. Although the first (steam-powered) dirigible flew in 1852, it was not until 1907 that the British army acquired one, which could fly for 24 hours at up to 50 knots. The Italians first used them in action during the Italo-Turkish war of 1912, and all sides developed airships before WW I. Airships built by Count Ferdinand von Zeppelin's company and the rival Shutte-Lantz flew 285 sorties over England, dropping 275 tons of bombs, and caused many British aircraft to be diverted from the front, but the use of highly inflammable hydrogen for lift doomed them once the fighters started using incendiary bullets.
The British abandoned research into dirigibles between the wars after the crash of the R-101 in 1930, but interest continued elsewhere. The USA had a world monopoly of helium, so the Germans continued to use hydrogen, resulting in the fiery death of the Hindenburg in 1937. However, they still used their allegedly civilian dirigibles to conduct military reconnaissance of the British coast prior to WW II. The US Navy lost interest after two enormous dirigibles, equipped with unique little biplane fighters that hung on hooks below them, went down at sea with the loss of all hands.
Although some dirigible ‘blimps’ were used by the US Navy for coastal patrols through the 1940s and 1950s, and the Bundeswehr used them to distribute propaganda leaflets in the Cold War, balloons and airships have all but faded from military use. Some limited trials have been conducted using blimps as platforms for airborne early warning radar, but their slowness and vulnerability limits their application.
— Peter Caddick-Adams
