The Yokosuka MXY-7 Ohka (櫻花, Ōka, "cherry blossom"; 桜花 in modern orthography) is a purpose-built,
rocket-powered human-guided kamikaze attack-aircraft deployed by Japan against
Allied ships in the Pacific Ocean theater towards the end of World War II.
Although extremely fast, the Ohka had a very short range, so it had to be
carried into action as a parasite aircraft by a much larger bomber, which was
itself vulnerable to carrier-borne fighters. In action during the Battle of
Okinawa in 1945, Ohkas succeeded in sinking or damaging some escort-vessels and
transport ships, but never sank any major warships. The Japanese developed
improved versions in an attempt to overcome the aircraft's shortcomings, but
they came too late for deployment.
Allied personnel referred to
the aircraft as "Baka Bombs" (baka being a Japanese pejorative term
meaning "fool" or "idiot").
Design and Development
The MXY-7 Navy Suicide
Attacker Ohka was a manned flying bomb that was usually carried underneath a
Mitsubishi G4M2e Model 24J "Betty" bomber to within range of its
target. On release, the pilot would first glide towards the target and when
close enough he would fire the Ohka's three solid-fuel rockets, one at a time
or in unison, and fly the missile towards the ship that he intended to destroy.
The design was conceived by
Ensign Mitsuo Ohta of the 405th Kōkūtai, aided by students of the Aeronautical
Research Institute at the University of Tokyo. Ohta submitted his plans to the
Yokosuka research facility. While Ohta had started work on the design in 1943
the authorities would not take an interest until the following year. The
Imperial Japanese Navy decided the idea had merit and Yokosuka engineers of the
Yokosuka Naval Air Technical Arsenal (Dai-Ichi Kaigun Koku Gijitsusho, or in
short Kugisho) created formal blueprints for what was to be the MXY-7. The only
variant which saw service was the Model 11, and it was powered by three Type 4
Mark 1 Model 20 rockets. 155 Ohka Model 11s were built at Yokosuka, and another
600 were built at the Kasumigaura Naval Air Arsenal.
The final approach was
difficult for a defender to stop because the aircraft gained high speed (650
km/h (400 mph) in level flight and 930 km/h (580 mph) or even 1,000 km/h (620 mph)
in a dive. Later versions were designed to be launched from coastal air bases
and caves, and even from submarines equipped with aircraft catapults, although
none were actually used in this way. The Allen M. Sumner-class destroyer USS
Mannert L. Abele was the first Allied ship to be sunk by Ohka aircraft, near
Okinawa on 12 April 1945. Over the course of the war, Ohkas sank or damaged
beyond repair three ships and significantly damaged three more ships, with a
total of seven U.S. ships damaged or sunk by Ohkas.
The Ohka pilots, members of
the Jinrai Butai (Thunder Gods Corps), are honored in Japan at Ohka Park in
Kashima City, the Ohka Monument in Kanoya City, the Kamakura Ohka Monument at
Kenchō-ji Zen temple in Kamakura, Kanagawa, and the Yasukuni Shrine in Tokyo.
The only operational Ohka was
the Model 11. Essentially a 1,200-kilogram (2,600 lb) bomb with wooden wings,
powered by three Type 4 Model 1 Mark 20 solid-fuel rocket motors, the Model 11
achieved great speed, but with limited range. This was problematic, as it
required the slow, heavily laden mother aircraft to approach within 37 km (20
nmi; 23 mi) of the target, making it very vulnerable to defending fighters.
There was one experimental variant of the Model 11, the Model 21, which had thin
steel wings manufactured by Nakajima. It had the engine of the Model 11 and the
airframe of the Model 22.
The Ohka K-1 was an unpowered
trainer version with water ballast instead of warhead and engines, that was
used to provide pilots with handling experience. Unlike the combat aircraft, it
was also fitted with flaps and a landing skid. The water ballast was dumped
before landing but it remained a challenging aircraft to fly, with a landing
speed of 130 mph (210 km/h). Forty-five were built by Dai-Ichi Kaigun Koku
Gijitsusho.
The Model 22 was designed to
overcome the short standoff distance problem by using a Campini-type motorjet
engine, the Ishikawajima Tsu-11, giving a level speed of only 276 mph at 13,125
feet but extending the range to 81 miles. This engine was successfully tested,
and 50 Model 22 Ohkas were built at Yokosuka to accept this engine. The Model
22 was to be launched by the more agile Yokosuka P1Y3 Ginga "Frances"
bomber, necessitating a shorter wing span and much smaller 600-kilogram (1,300
lb) warhead. The first flight of a Model 22 Ohka took place in June 1945; none
appear to have been used operationally, and only approximately 20 of the
experimental Tsu-11 engines are known to have been produced.
The Model 33 was a larger
version of the Model 22 powered by an Ishikawajima Ne-20 turbojet with an
800-kilogram (1,800 lb) warhead. The mothership was to be the Nakajima G8N
Renzan. The Model 33 was cancelled due to the likelihood that the Renzan would
not be available.
Other unbuilt planned
variants were the Model 43A with folding wings, to be launched from submarines,
and the Model 43B, a catapult/rocket-assisted version, also with folding wings
so that it could be hidden in caves. A trainer version was also under
development for this version, the two-seat Model 43 K-1 Kai Wakazakura (Young
Cherry), fitted with a single rocket motor. In place of the warhead, a second
seat was installed for the student pilot. Two of this version were built.
Finally, the Model 53 would also use the Ne-20 turbojet, but was to be towed
like a glider and released near its target.
Operational History
The Yokosuka MXY-7 Ohka was
used mostly against U.S. ships invading Okinawa, and if launched from its
mothership, could be effective because of its high speed in the dive. In the
first two attempts to transport the Ohkas to Leyte Gulf using aircraft
carriers, the carriers Shinano and Unryu were sunk by the U.S. submarines
Archerfish and Redfish.
Attacks intensified in April
1945. On 1 April 1945 six G4Ms attacked the U.S. fleet off Okinawa. At least
one made a successful attack; its Ohka was thought to have hit one of the 406
mm (16 in) turrets on the battleship West Virginia, causing moderate damage.
Postwar analysis indicated that no hits were recorded and that a near-miss took
place. The transports Alpine, Achernar, and Tyrrell were also hit by kamikaze
aircraft, but it is unclear whether any of these were Ohkas from the other
G4Ms. None of the G4Ms returned.
The U.S. military quickly
realized the danger and concentrated on extending their "defensive
rings" outward to intercept the G4M/Ohka combination aircraft before the
suicide mission could be launched. On 12 April 1945 nine G4Ms attacked the U.S.
fleet off Okinawa. The destroyer Mannert L. Abele was hit, broke in two, and
sank. Jeffers destroyed an Ohka with AA fire 45 m (50 yd) from the ship, but
the resulting explosion was still powerful enough to cause extensive damage,
forcing Jeffers to withdraw. The destroyer Stanly was attacked by two Ohkas.
One struck above the waterline just behind the ship's bow, its charge passing
completely through the hull and splashing into the sea, where it detonated
underwater, causing little damage to the ship. The other Ohka narrowly missed
(its pilot probably killed by anti-aircraft fire) and crashed into the sea,
knocking off the Stanly's ensign in the process. One Betty returned. On 14
April 1945 seven G4Ms attacked the U.S. fleet off Okinawa. None returned. None
of the Ohkas appeared to have been launched. Two days later, six G4Ms attacked
the U.S. fleet off Okinawa. Two returned, but no Ohkas had hit their targets.
Later, on 28 April 1945, four G4Ms attacked the U.S. fleet off Okinawa at
night. One returned. No hits were recorded.
May 1945 saw another series
of attacks. On 4 May 1945 seven G4Ms attacked the U.S. fleet off Okinawa. One
Ohka hit the bridge of a destroyer, Shea, causing extensive damage and
casualties. Gayety was also damaged by an Ohka's near miss. One G4M returned.
On 11 May 1945 four G4Ms attacked the U.S. fleet off Okinawa. The destroyer
Hugh W. Hadley was hit and suffered extensive damage and flooding. The vessel
was judged beyond repair. On 25 May 1945 11 G4Ms attacked the fleet off
Okinawa. Bad weather forced most of the aircraft to turn back, and none of the
others hit targets.
On 22 June 1945 six G4Ms
attacked the fleet. Two returned, but no hits were recorded. Postwar analysis
concluded that the Ohka's impact was negligible, since no U.S. Navy capital
ships had been hit during the attacks because of the effective defensive tactics
that were employed. In total, of the 300 Ohka available for the Okinawa
campaign, 74 actually undertook operations, of which 56 were either destroyed
with their parent aircraft or in making attacks. The Allied nickname for the
aircraft was "Baka", a Japanese word meaning "foolish" or
"idiotic".
Variants
MXY-7: Rocket
powered suicide attacker, unpowered glider prototypes; ten built
Navy Suicide Attacker Ohka Model 11: Long designation of the operational attacker
Ohka Model 11: Suicide
attacker powered by 3 × 2.616 kN (588 lbf) Navy Type 4 Mark 1 Model 20
solid-fueled rocket motors, firing for 8–10 seconds; 755 built
Ohka Model 21: Suicide
attacker, fitted with steel-built wings built by Nakajima; one built
Ohka Model 22: Suicide
attacker, powered by an Ishikawajima Tsu-11 thermo-jet engine with reduced span
wings and 600 kg (1,300 lb) warhead, to be carried by Yokosuka P1Y1 Ginga
bombers. 50 built by the First Naval Air Technical Arsenal (第一海軍航空技術廠, Dai-Ichi Kaigun Koku Gijitsusho)
Ohka Model 33: Suicide
attacker, powered by an Ishikawajima Ne-20 turbojet engine, with an 800 kg
(1,800 lb) warhead, to be carried by the Nakajima G8N1 Renzan bomber
Ohka Model 43A Ko: Suicide attacker, powered by a Ne-20 turbojet engine, with folding
wings, to be catapult launched from submarines
Ohka Model 43B Otsu: Suicide attacker similar to the Model 43A for catapult
launching from caves
Ohka Model 53: Suicide
attacker for aerotow launch, powered by a Ne-20 turbojet engine
Ohka K-1: Suicide
attack training glider
Ohka Model 43 K-1 Kai Wakazakura (若桜, "Young Cherry"): Two-seat suicide attack glider trainer with flaps and
retractable skid undercarriage, fitted with a single Type 4 Mark 1 Model 20
rocket motor, for limited powered flight
"Suzuka-24" (Japanese designation unknown): Alleged interceptor version with warhead replaced by a
fuel tank for a Ne-20 jet engine and two 20 mm autocannon (Unknown Ho-5 or Type
99 with 60 / 150 rounds per gun) mounted on top. Supposedly employed at least
twice against B-29 formations in April 1945
Bibliography
Aeronautical Staff of Aero
Publishers in cooperation with Edward T Maloney (1966). Kamikaze. Fallbrook,
California, USA: Aero Publishers.
Ellis, Ken. Wreck &
Relics, 23rd Edition Manchester: Crecy Publishing Ltd, 2012.
Francillon, René J. (1979).
Japanese Aircraft of the Pacific War (2nd ed.). London: Putnam & Company.
Francillon, René J. (1971).
Mitsubishi G4M "Betty" and Ohka Bomb. Aircraft in Profile, Vol. 9.
Windsor, Berkshire, UK: Profile Publications Ltd.
Maloney, Edward T. and the
Aeronautical Staff of Aero Publishers, Inc. Kamikaze (Aero Series 7).
Fallbrook, California: Aero Publishers, Inc., 1966.
Mikesh, Robert C.; Abe,
Shorzoe (1990). Japanese Aircraft, 1910–1941. London: Putnam Aeronautical
Books.
O'Neill, Richard (2001).
Suicide Squads: The Men and Machines of World War II Special Operations.
Washington DC: The Lyons Press.
Sheftall, M.G. Blossoms in
the Wind: Human Legacies of the Kamikaze. New York: New American Library, 2005.
Stafford, Edward P. Little
Ship, Big War: The Saga of DE343. Annapolis, Maryland: Naval Institute Press,
2000.
Zaloga, Steven J. (2011).
Kamikaze: Japanese Special Attack Weapons 1944–45. New Vanguard #180. Botley,
Oxfordshire: Osprey Publishing.
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An Ohka Model 11 being disarmed. Possibly the I-13 captured April 1, 1945 at Yontan airfield. |
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Notice intake ducts for the jet Engine on the side just forward of the tail section. This is an experimental Model 22 which never went into production. From the background hangers, this appears to be taken at Yokosuka Naval base where all model 22's were built. It is unlikely the Model 22 could have been anywhere else since testing of the integration of troublesome Tsu-11 jet engine occured here. Unlike the Alameda example now in the NASM, this unit has intact ducts and appears from the exhaust tube to have one of the 3 TSU-11 hybrid Jet engines known to have been produced.
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MXY7 K-1 Kai Two-seat trainer powered by a single Type 4 Mk I Model 20 rocket motor and fitted with flaps and landing skis; 2 built at Yokosuka. These are the two being inspected by Navy personnel.
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Yokosuka Ohka Model 22. |
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Yokosuka MXY-7 Ohka ("Baka" bomb) being towed behind a truck after its capture, 20 April 1945. Note insignia and coding, I-13. |
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Yokosuka MXY-7 Ohka ("Baka") piloted flying bomb which had been captured on Okinawa. Photographed 26 June 1945, while under study by experts at N.A.M. (Navy Air Material) Unit. |
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Yokosuka MXY-7 Ohka piloted flying bomb which had been captured intact by Marines on Okinawa, while under study by experts at N.A.M. Unit. 26 June 1945. |
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Yokosuka MXY-7 Ohka which had been captured intact by Marines on Okinawa. Photographed while under study by experts at N.A.M. Unit. 26 June 1945. |
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Yokosuka MXY-7 Ohka piloted flying bomb which had been captured intact by Marines on Okinawa, while under study by experts at N.A.M. Unit. 26 June 1945. |
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A Japanese MXY-7 Model 11 Okha suicide plane captured on 1 April 1945 at Yontan airfield, Okinawa. |
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MXY7 Model 11 Manufacture Number 1049 Number I-18 captured April 1, 1945 at Yontan airfield, Okinawa. |
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Yokosuka MXY7 Ohka, Okinawa, 1 April 1945. |
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Japanese Yokosuka MXY-7 Ohka "Baka" flying bomb on the deck of USS Core (CVE-13) as part of a shipment of Japanese warplanes being loaded in Japan, 21 November 1945. Note that this is a two seat training glider version of the "Baka". Plane in background is a Mitsubishi Ki-67 "Peggy" bomber. |
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Yokosuka MXY-7 Ohka "Baka" flying bomb on the deck of USS Core (CVE-13) as part of a shipment of Japanese warplanes being loaded in Japan, 21 November 1945. |
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Yokosuka MXY7 Ohka rocket motor. |
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Stills from gun camera footage of an attack on an Imperial Japanese Navy Mitsubishi G4M2e Model 24 Tei ("Betty") bomber carrying a Kugisho/Yokosuka MXY-7 Ohka ("Baka") Model 11 manned rocket-propelled suicide plane. |
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Mitsubishi G4M2E Model 24 Tei bomber from Kokutai 721 carrying an Ohka. |
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Imperial Japanese Navy Stand-by aircrews relax in front of a Mitsubishi G4M2e Model 24 Tei ("Betty") bomber carrying a Kugisho/Yokosuka MXY-7 Ohka ("Baka") Model 11 manned rocket-propelled suicide plane. |
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Mitsubishi G4M2E Model 24 Tei bomber just released MXY7 Ohka.
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Yokosuka MXY-7 Ohka ("Baka" bomb) control panel, April 20, 1945. [National Archives 80-G-192464]
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A MXY-7 Ohka Model 22 at Yokosuka minus its wings. Note the air intakes indicating jet, not rocket power, 1945.
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Cockpit of a captured model 11, from the angle of the wings. (Model 22 were swept back more).
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A Yokosuka MXY-7 Ohka at the Yokosuka naval district, in September 1945. |
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Yokosuka MXY7 Ohka human-guided anti-shipping kamikaze attack planes at Kōnoike Airfield, Kashima, Ibaraki, Japan, August 1945.
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