Less than a dozen years after the first manned balloon flights, the first aerial observation of a battlefield contributed to the French victory at Fleurus in June 1794. Although a short-lived initiative, the operation displayed the value of viewing a battle from so lofty a perch and responding to inquiries from the ground in near-real-time. Thaddeus Lowe’s tethered aerial observation during the American Civil War supported Union operations for almost two years, but problems with personal finances and continuing bickering with rival balloonist John LaMountain eventually led to the Balloon Corps’ quite dissolution. Against the Boers in South Africa, British Army balloonist observations were reported immediately (often by megaphone). The Boers were no more successful in trying to shoot down balloons than Confederate gunners had been.

Balloon and kite flying saw limited development, but the 1908 demonstration of the Wrights’ success in heavier-than-air flight to the U.S. Army and dozens of cheering crowds in Europe underscored the airplane’s potential for aerial reconnaissance to the military in several countries. The year 1911 saw aerial reconnaissance (and bombing) in locales as diverse as Mexico (using a rented flying circus), Libya, and the Balkans.

World War I saw the first widespread use of aircraft for both tactical and strategic reconnaissance. Indeed, the two levels could be said to have combined forces early when timely observation of German movements in September 1914 led first to the preservation of the British Expeditionary Force from extinction and later to the French victory at the Battle of the Marne. Stalemated by each other in their rush to an early decision, the two sides dug in.

Fixed-wing aircraft added unprecedented altitude and mobility on every front.

Under such conditions, airplanes replaced cavalry as the army’s eyes in the flying machine’s greatest contribution to the war effort. France produced most of the Allies’ nearly 4,000 tethered observation balloons, which soared from 1,200 to 1,800 feet and commanded a 15-mile view in good weather. The gasbag crew’s snooping and ability to correct the artillery’s aim led to aerial attacks against them as well as concentrated anti-aircraft support (“Archie”).

Fixed-wing aircraft added unprecedented altitude and mobility on every front. Almost as soon as recce flights began, observers began taking pictures by leaning over the side with hand-held, short-focal-length cameras using glass-plate film. It was cold, often dangerous work at oxygen-thin altitudes. German designers in particular developed fast, high-flying maneuverable two-seaters for this mission. Some, like the Rumpler C series and Halberstadt’s C.V had trap doors in the floor for vertical photography, a feature also found on the Salmson 2 flown by French and American crews. British designed such as the BE 2 series and RE 8 fell far short of even adequacy. By 1918, German crews were snapping up to 4,000 photographs per day, four times as many as the British average; their audacity was bolstered by a prevailing Westerly wind that blew damaged aircraft back over friendly lines.

As critical as taking the photography was processing it quickly and comprehensibly. This meant careful handling of the fragile glass plates and accomplishing a speedy handover once back on the ground. Good observers and pilots noted the time, altitude, and circumstances of each shot for the photo interpreter, whose worth grew explosively with demand. By 1918, for example, the U.S. Army printed 56,000 aerial photos in support of the Meuse-Argonne offensive in four days.

After World War I American George Goddard pursued improvements that led to vibration damping, stereoscopic photo technique, infrared, color and night photography (the latter including development of photo-electric shutter release), and longer focal-length lenses, improved cameras taking sharper pictures.

Perhaps Goddard’s most important breakthrough came in the 1930s with the strip camera. Instead of taking individual frames and stitching them together, the strip camera synchronized the roll film’s passage past a slit. Resistance to the technology, delayed its use for years, but strip-filming was the major Cold War aerial photo-reconnaissance method.

Increasing tensions in the late 1930s prompted covert photo reconnaissance by both Germana and British pilots. German Lt. Col. Theodor Rowehl took pictures over Britain, France, and the Soviet Union from a Heinkel He 111. On the Allied side, the distinctly individual Sidney Cotton, an Australian who’d gained aerial reconnaissance expertise in Canada, cooperated with Britain’s MI6 in flying modified Lockheed 12 Electra aircraft over Italy and Germany under cover as a aeronautical product salesman. His aircraft had three main cameras, one for vertical, two for oblique photography arranged to produce 3-dimensional imagery when the photographs were overlapped. This arrangement or variations was used throughout World War II.

Cotton’s special flight of modified Spitfires soon set the tone for Anglo-American photo reconnaissance. The most successful Allied photo reconnaissance aircraft were modified unarmed fighters or light bombers outfitted with several cameras that depended on waxed, smoothed surfaces, weight reduction, and tweaked engines to fly fast and very high over most of the continent. The best known of the British planes were several marks of the Spitfire, although PR veterans regarded the twin-engined Mosquito, which also served in considerable numbers, as more suitable. The best U.S. aircraft was the F-5 conversion of the P-38 Lightning, which was delivered in far greater numbers than any other reconnaissance design. U.S. Navy reconnaissance fliers made the first use of the continuous strip camera in 1944.

Picture-snapping had little value without organized, centralized photo interpretation on the ground. In addition to their bomb damage assessment, photo interpreters on the ground. In addition to their bomb damage assessment, photo interpreters comparing pictures taken on the same target at intervals became adept at detecting differences that might mean troop movement in or out of an area; construction progress of a ship, factory, or military base; or alterations implying upgraded capabilities. Their efforts tracked German jet aircraft research, deployment of the first German radar, and the V-1 flying bomb. By the end of World War II, British and U.S. aerial reconnaissance was indispensable to both tactical and strategic planning.

In the half-century that followed Germany and Japan’s surrender, aerial reconnaissance became overhead reconnaissance, photography became imagery, emissions of all sorts became the object of remote surveillance, and more and more natural and human activities became the object of remote observation.

In the first postwar decade, U.S. and British reconnaissance was driven by an urgency to ascertain the threat contained by the vast, sealed reaches of first the Soviet Union and later “Red” China. At first aircraft were mostly bomber conversions limited mostly to sniffing around the edges; several dozen crew were killed or captured in largely unpublicized incidents. Much of the reconnaissance was electronic that sampled emissions and built signature libraries.

Fear of Soviet surprises drove the development of overhead reconnaissance. Although satellites were planned from the late 1940s, many technical hurdles remained. In the interim, other means of getting a camera over a target were tried. A thousand or so camera-carrying balloons were launched from Britain, Germany, and Turkey; only 55 were recovered. As camera and film technology improved, aircraft were modified to take the equipment higher to see farther while staying out of reach of intercepting aircraft or missiles. In addition, sensors were looking in the near and far infrared (IR) parts of the electromagnetic spectrum, as well as the shorter-wave segment imaged by radar.

Lockheed developed first the U-2 and later the SR-71 as the ultimate overflying reconnaissance aircraft. The U-2 was a jet-powered glider that flew at 80,000 feet and could fly over much more of the Soviet Union taking photos of ever-finer resolution. Ironically, proof of the non-existence of a “bomber gap” could not be offered publicly for fear of demonstrating just how good the photographic technology was. And a promising thaw in Cold War relations was aborted when an overflying U-2 was shot down by a Soviet missile in May 1960. Already in development was the SR-71, a Mach 3 aircraft flying at nearly 85,000 feet. Entering service in the mid-1960s, the SR-71 quickly established its virtual immunity to interception and gathering imagery at the rate of 100,000 sq. miles per hour – to date, no other airplane has regularly flown so fast or so high.

But the next jump in remote reconnaissance had already been taken. On the same day in August 1960 that downed U-2 pilot Francis Gary Powers  was convicted as a spy in the Soviet Union, the U.S. recovered the first film capsule to have been jettisoned from an orbiting satellite. Invulnerable to interception, reconnaissance satellites have taken on the lion’s share of imaging, signals, electronic, and communications intelligence gathering. They were at first constrained by the need to physically return the film for processing. Development of Charged-Couple Devices that allow translation of images into digital streams of data permitted near-real-time intelligence almost anywhere in the world – weather permitting.

Soon analysts realized that such observation could be used to reinforce stability by allowing independent verification that treaty conditions were being met or that rumored new developments either happened more slowly than feared or not at all. In the United States, a vast infrastructure supporting the launch, use, maintenance, and replacement of intelligence satellites reached enormous (and unpublicized) proportions. Soviet reconnaissance satellites soon joined U.S. satellites in a variety of orbits and missions.

Of equal importance was the deployment of satellites that allowed better weather forecasting, earth resources analysis, assessment of environmental changes, even remote identification of archeological sites of interest. Much of the imagery was released under constraints imposed by the intelligence communities of the NATO and Warsaw Pact blocs. This began to break down, however in the 1980s, when the duopoly was successfully challenged by the SPOT commercial satellite. SPOT’s relative independence from control offered a way to investigate independently events in remote locations. The Chernobyl nuclear reaction explosion in April 1986 was one of the first instances where SPOT imagery was used by the media when other views were not made available.

At the tactical and theater levels, most militaries converted twin- or four-engined transports into reconnaissance platforms. Best-known were the U.S. RC-135 series, which proliferated into dozens of variants, and the Lockheed EP-3 series, the Soviet Il-18 “Coot,” and the British Nimrod. Fighters frequently had a reconnaissance counterpart that carried a battery of cameras. In the 20th century’s last decade, aerial reconnaissance platforms mirrored the variety of types and missions increasingly found in satellites.

Another trend that grew more strongly in the last few decades has been the use of remotely piloted unmanned aircraft. First used in large numbers to support U.S. air operations over Vietnam, these aircraft typically were jet-powered and fast. Several designs were for produced for battlefield reconnaissance along the NATO-Warsaw Pact divide in Europe. Later miniaturization of cameras and control technology, much of it due to the introduction of microchips, led to smaller, slower air vehicles which were exported to many other countries. Many latter-day conflicts included UAV flyovers as an integral part of strike assessment and planning as well as compliance monitoring.

In the first decade of the 21st century, overhead reconnaissance by satellite predominates, especially to provide comparative cover. For rapid updates of the battlefield as well as continued sampling of the broad spectrum of electromagnetic emissions, aerodynamic air vehicles are still needed. More and more, however, these may be unmanned. Such UAVs can range from micromachines that fit in the palm of a hand to the Global Hawk or NASA’s solar-powered Pathfinder, which spans 200 feet and can fly for days. The UAV trend promises to reproduce the origins of manned aerial combat.

This article was first published in Aviation 100: Celebrating a Century of Manned, Powered Flight – Volume 2