AIR POWER History / FALL 2021 7 Looking Back from the Age of ISR: U.S. Observation Balloons in the First World War Donald M. Bishop & Erik R. Limpaecher E ach of the U.S. armed services has programs underway to apply stratospheric balloons to intelligence, surveillance, and reconnaissance (ISR) and communications missions. This is because stratospheric balloons, which operate at 60,000 to 100,000 feet altitude, can provide persistent communications and surveillance coverage over miles of ter- ritory. They operate at a fraction of the cost of powered aerial vehicles and can loiter over an area for half a day to multiple days. 1 Several of these programs plan to use hydrogen gas to loft their balloons to the stratosphere. This renewed interest in the use of hydrogen-filled balloons for high altitude applications opens yet another page in the military use of lighter-than-air aircraft. This history has many fascinating chapters. Among them are the occasional use of balloons, without much effect, on battlefields from the French Revolution to the Crimean War; use of observation balloons by the Union and Confederate armies Army during the Civil War; balloon reconnaissance in the Spanish-Amer- ican and Russo-Japanese Wars; 2 and balloon races. The First World War saw the use of observation balloons at the front, used by all sides; use of other balloons at sea; 3 balloon barrages and balloon aprons for point defense of high-value targets against air attack; 4 and Zeppelins for bombardment. Since the Great War, use of lighter-than-air vehicles included diri- gibles and airships; experiments in high-altitude ballooning in the 1930s; both defensive barrage balloons and offensive small balloons carrying incendiaries and anti-power grid cables in the Second World War; 5 tethered aerostats to help protect forward operating bases and provide aerial views of war-torn cities in Iraq and Afghanistan; and radar aerostats along the southern land and maritime borders of the United States. Examining the experience of the American Expeditionary Forces in France in 1917 and 1918, most of the Air Service glory went to the aces and the fighter pilots in winged aircraft, but American soldiers and Marines knew that the AEF’s balloon companies, equipped with Goodyear R-4 Caquot balloons, were vital on the battlefield. (Because they were teth- ered, these balloons would now be classed as aerostats, but that name lay in the future.) Indeed, “when the balloon goes up” is still Air Force lingo for “when the fight begins.” 6 Reviewing the use of these hydrogen-filled U.S. observation balloons in combat accords with a key insight of the 2018 National Defense Strategy – “deepening our knowledge of history while embracing new technology and techniques to counter competitors.” 7 It throws in high relief the progress of technology since the Great War ended more than a century ago. And it offers useful perspectives on the use of hydrogen – a flammable gas – in modern lighter-than-air aircraft. “Operating a Balloon in France: Tenth Balloon Company in Ac- tion.” (Photo from Camp John Wise Aerostation website.)