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Kashima Ōka Park
Kashima City, Ibaraki Prefecture

A small park lies a short distance to the right of the main gate of the massive Sumitomo Metals foundry in Kashima City, located about two hours east of Tokyo Station by bus. During World War II, the park's site was part of Kōnoike [1] Naval Air Base, the training base for pilots of the ōka, a rocket-powered glider used for suicide attacks on Allied ships. This park now has a monument to the ōka pilots and a World War II underground hangar with a restored Yokosuka Ōka Model 11.

The 721st Naval Air Group, also known as the Thunder Gods Corps (Jinrai Butai), formed at Hyakurihara Air Base in Ibaraki Prefecture on October 1, 1944. The Corps transferred to Kōnoike Air Base, in the southern part of Ibaraki Prefecture, on November 7, 1944, and this remained the location for ōka testing and pilot training until the end of the war. Pilots practiced on K-1 trainers with retractable landing skids and with water used as ballast equal in weight to the 1.3-ton warhead carried in the ōka's nose.

The ōka glider, constructed of wood and non-critical metal alloys, could reach a speed of 600 mph as it accelerated toward its target with three rocket engines mounted in its tail. A mother plane carried the ōka underneath its body and then released it when reaching a point near the intended target. The Model 11 ōka, the only one of four models ever used in battle, had a length of 20 feet and a wingspan of 17 feet (Francillon 1979, 476-82).

On January 28, 1945, members of the 721st Naval Air Group started to move to Japan's southernmost island of Kyushu to start preparations for suicide attacks on American ships. The first attack took place from Kanoya Naval Air Base on March 21, but American planes intercepted all of the 15 Betty bombers carrying ōka gliders before they could get close enough to be released toward American ships. During the Battle of Okinawa, the ōka weapons achieved little success in battle, sinking only one American destroyer and damaging eight other ships (O'Neill 1999, 160). "Of the total of 185 planes used in Ōka attacks, 118 were destroyed, taking the lives of 438 persons, including 56 Thunder Gods pilots and 372 mother-plane crew members" (Naito 1989, 182).

The Ōka Monument was erected in 1978 through the efforts of a former member of the Ōka Corps and his wife. The monument originally stood at a site near the current park, but it was moved in 1993 when Sumitomo Metals donated the park land together with an underground hangar (entaigō) used during World War II to protect a plane from enemy air attacks. Although dozens of these underground hangars existed at Kōnoike Air Base during the war, this is the only one that remains today.

The monument prominently displays the two characters for "ōka," meaning "cherry blossom" in Japanese. The right side of the monument has the words, "Training Site for Jinrai Butai (Thunder Gods Corps) and Tatsumaki Butai (Tornado Corps) Ōka Corps Members." Tatsumaki Butai, the nickname for the 722nd Naval Air Group, was the ōka unit organized to train new pilots at Kōnoike Air Base to replace those expected to die in the 721st Thunder Gods Corps.

Restored Ōka Model 11
with cherry blossom painted on side 


Although I visited Kashima Ōka Park on a freezing day in January, several vases of white flowers had been placed in front of the Ōka Monument. The park also has several cherry trees donated by the Thunder Gods Association. The couple who led the efforts to build this monument in Kashima also erected an Ōka Monument in Kanoya in 1978.


1. Naito (1989) and Hagoromo Society (1973) use the romanization of "Kōnoike" for the air base's name, but "Gōnoike" is the pronunciation indicated in signs at the park, a brochure published by Kashima City, and another brochure by the nearby Kamisu Historical Museum. "Gōnoike" is another possible romanization of the Japanese name.

Sources Cited

Francillon, René J. 1979. Japanese Aircraft of the Pacific War. Annapolis: Naval Institute Press.

Hagoromo Society of Kamikaze Divine Thunderbolt Corps Survivors. 1973. The Cherry Blossom Squadrons: Born to Die. Edited and supplemented by Andrew Adams. Translated by Nobuo Asahi and the Japan Tech Co. Los Angeles: Ohara Publications.

Naito, Hatsuho. 1989. Thunder Gods: The Kamikaze Pilots Tell Their Stories. Translated by Mayumi Ishikawa. Tokyo: Kodansha International.

O'Neill, Richard. 1999. Suicide Squads: The Men and Machines of World War II Special Operations. Originally published in 1981. London: Salamander Books.