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designed to gather intelligence,
usually by visual observation, aerial photography, or radar. While almost any
aircraft had significant reconnaissance capability, the ideal
aircraft was capable of flying high and fast to avoid interception by fighters and
had a long range. Combat capability was much less important.
Strategic reconnaissance missions were flown by long-range aircraft with high-resolution photographic equipment. Of these, the best was probably the Japanese Ki-46 Dinah, whose combination of speed, service ceiling, and range made it nearly the ideal reconnaissance aircraft. Allied fighter pilots found it extremely difficult to intercept, and Dinahs participated in the photoreconnaissance of Malaya and the Philippines before the war and on missions over Ulithi and Okinawa in its final months. The closest Allied equivalent was the reconnaissance version of the British Mosquito, which because it was made largely of plywood had a low radar cross-section, making it arguably the first stealth aircraft.
There were not enough Mosquitos to go around, and
Allied strategic reconnaissance in the Pacific tended to depend on
bomber aircraft converted to
reconnaissance duty. The most important of
these in the early days of the war was the A-28 Hudson, which had little to
recommend it except its availability. However, an Australian Hudson crew succeeded in
obtaining the first photographs of the main Japanese base at Truk, a mission that must have required
the utmost courage. Later in the war, strategic reconnaissance was
carried out largely by heavy
bombers such as the B-17
Flying Fortress and
the B-24 Liberator. In
addition to overhead photographs taken from high altitude, these
aircraft began taking oblique photographs from very low altitude that
gave a ship's-eye view of invasion
An oddball exception to this rule was the F-7, a photoreconnaissance version of the Wildcat fighter that sacrificed armament and armor for a large camera and immense fuel tanks. The F-7 had a range of over 2000 miles (3200 km) and was equipped with both an autopilot for such long missions and a fuel dump system that allowed it to unburden itself if it had to skedaddle in a hurry. Originally designed to operate from carriers, it saw little service in this role (being unsuited for tactical reconnaissance), but a few F-7s operated from Henderson Field at Guadalcanal and scouted the Japanese base at Rabaul.
Though the F-7 was not a success, the Navy perceived that aircraft participating in deep penetration carrier raids could gather valuable strategic intelligence for later operations. This led to deployment of the F6F-5P Hellcat, which carried a camera in its lower left fuselage. Unlike the F-7, the F6F-5P retained its armament and almost all of its performance, allowing it to gather intelligence while participating in normal combat operations. By the time of the Okinawa operation, most carrier fighter squadrons included one or two of the -5Ps. Likewise, the TBM-3P Avenger carried cameras in its bomb bay, but this may have prevented its use for normal combat missions, and only a few torpedo squadrons were equipped with a single-3P.
Photoreconnaissance typically was carried out in daylight using film sensitive to visible wavelengths of light. However, the Japanese may have used infrared film for nighttime photoreconnaissance as early as the first Philippines campaign (Creed 1985). The aerial camera most widely used by American forces was the Fairchild K-17, which produced 9" by 9" (229mm by 229mm) images on a long roll of film using a 6" (152mm) lens with a 6", 12", or 24" (152mm, 305mm, or 610 mm) focal length. The film magazine carried enough film for 250 exposures, could take a picture every 3 seconds, and used a vacuum arrangement to hold the film tightly in place for a sharp image. The complete camera with film magazine weighed 55 lbs (25 kg), which would have been awkward when using the camera with the viewfinder advertised for "handheld operation."
Long-range tactical reconnaissance over the
Pacific Ocean was often carried out by flying boats, such as the
Japanese H6K Mavis and H8K Emily or the American PBY Catalina. Japanese flying
boats were huge and heavily armed and armored and carried out
reconnaissance throughout the war. Allied flying boats, with the
exception of the Sunderland
(known as the Porcupine for its heavy defensive armament), were
vulnerable and increasingly yielded the reconnaissance role to heavy
bombers as the war progressed. These aircraft were equipped with ASV radar by the end of 1942, a technology in which the Japanese trailed far behind the Allies.
Short-range tactical reconnaissance at sea was
carried out by light bombers
on the American side and seaplanes
on the Japanese side. The
produced a number of excellent seaplanes, including the E13 Jake and the E16 Paul, and many of their surface
warfare ships (particularly the Tone class heavy cruisers) were given
extensive seaplane hangars. However, the Japanese leaned more
on light bombers for reconnaissance as the war progressed. American
carrier air groups initially included a squadron of dive bombers designated for
scouting duty, but this designation became meaningless early in the war
as scouting was performed by whatever aircraft were available. Later in
the war, radar-equipped TBF Avenger
torpedo bombers did much of
the American tactical scouting at sea.
Prior to war, both sides assumed that seaplanes from surface warfare ships would play an important role in spotting for gunfire. This turned out not to be the case. Most surface engagements were fought at night, and Allied radar quickly proved itself capable of detecting large-caliber shell splashes. The Japanese, who had inferior radar, relied on seaplanes to drop flares during night engagements at least until 1943. Meanwhile, the U.S. Navy removed seaplanes from most surface warfare ships to eliminate the considerable fire danger associated with having a large, fragile, gasoline-filled object on their decks.
Both sides produced specialized light reconnaissance aircraft for their aircraft carriers, and neither side made much use of them when war came. The American F-7 has already been described. The Japanese produced the C5M Babs and the C6N Myrt as carrier reconnaissance aircraft, but, like the Americans, quickly found them unsuitable for tactical scouting and relegated them to land bases.
Tactical reconnaissance on land called for light aircraft that could hover over the target area for hours. Helicopters would have been ideal in this role, but only the Japanese Ka-1 and American R-4 Hoverfly came into operational service before the war ended, and only in small numbers. Instead, observation aircraft like the Ki-36 Ida and the O-47 served in this role. Curiously, it was the U.S. Navy that came up with the best observation aircraft, the OS2U Kingfisher, which could remain in the air for hours at a speed of just 70 miles per hour (113 km/h). A few operated from land bases in the Aleutians, but most operated from battleships, where their abilities were largely wasted.
Given the quality of Japanese photoreconnaissance aircraft,
it is strange that the Japanese used their photoreconnaissance so
unimaginatively. Japanese officers "didn't consider photography to be
useful operationally beyond the immediate tactical phase and apparently
made no effort to use photos in planning or anticipating new offensive"
(Evans and Peattie 1997). This combined with the lack of an integrated
vertical organization for collating intelligence to negate Japanese
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