Tsukuba Kaigun Kōkūtai

Text: Jan Bobek

Illustration: Piotr Forkasiewicz

Cat. No. 82218

The aircraft of the Japanese naval air group Tsukuba (Tsukuba Kaigun Kōkūtai) are probably known to many modelers because of the distinctive "Tsu" character on their tails. This training Kōkūtai underwent several organizational changes during its service. Toward the end of the war, it formed a fighter unit for homeland defense as well as several kamikaze units.

Its history began at Tomobe airfield, northwest of Lake Kasumigaura in Ibaraki Prefecture. In the early 1930s, the base was built on the site of a defunct sheep farm. Various army and naval units had previously operated from this area. In the summer of 1934, a detachment from the Kasumigaura Kōkūtai training unit started operations at the new base. This detachment conducted basic flight tests, after which successful naval academy graduates and non-commissioned officers were assigned to advanced training.

In December 1938, a new naval training unit, Tsukuba Kōkūtai, was established from the Tomobe detachment. A year later, a detachment from Tsukuba at Hyakurihara airfield became the Hyakurihara Kōkūtai.

In March 1944, a significant reorganization took place involving Tsukuba Kōkūtai. Its focus shifted to operational training on combat aircraft, and it took over equipment from the disbanded Ōita Kōkūtai. At the same time, it transferred its previous training aircraft to another naval unit, Tsukijō Kōkūtai.

One of the many commanders of Tsukuba Kōkūtai from July 1944 was Capt. Chujirō Nakano, who had previously commanded Kōkūtai 201 during defensive battles in the Rabaul area. Lt. Cdr. Yasushi Yokoyama also played a key role in the transition to combat aircraft training, taking over as head of training at Tsukuba Kōkūtai in July 1944.

With the introduction of single- and two-seat Zero aircraft, the grass runway at Tomobe was no longer adequate, and the unit relocated to Misawa airbase. In the second half of 1944, Tsukuba Kōkūtai also received Shiden (George II) fighters and in November formed a fighter unit composed of instructors. This unit first engaged the enemy on January 9, 1945, during a B-29 bombing raid on Tokyo, but did not shoot down any bombers.

In mid-February, the unit received 24 additional Zero fighters and had nine operational Shiden aircraft. Around the same time, Tsukuba Kōkūtai pilots clashed with U.S. Navy aircraft during raids on the Kantō region on February 16 and 17. Despite losing 14 aircraft, the Japanese pilots claimed 11 American planes shot down during the two days. In a similar engagement on February 25, Tsukuba Kōkūtai lost eight aircraft but claimed five victories. After the battle, only nine operational fighters remained.

At the same time, Tsukuba Kōkūtai was ordered to form a special kamikaze attack unit. Initial training took place at Kashima Kōkūtai, and by the end of March, eight special attack units had been formed.

On March 30, twelve aircraft from Tsukuba Kōkūtai were detached and moved to Izumi airbase. Their mission was to provide air cover for the battleship Yamato during Operation Ten-Ichi Go, a one-way voyage to Okinawa on April 6 and 7, 1945. Japanese planes were deployed for conventional and kamikaze attacks against Allied vessels pursuing Yamato. Among the ships hit were the aircraft carrier USS Hancock, the battleship USS Maryland, and the destroyer USS Bennett, which was heavily damaged.

Simultaneously, the Kikusui I kamikaze campaign against ships around Okinawa began. On its first day, April 6, a special attack unit from Tsukuba Kōkūtai participated in kamikaze attacks. By June 1945, another seven kamikaze units formed from Tsukuba Kōkūtai were deployed. From early May, Shiden aircraft began escorting these missions, increasing the Tsukuba Kōkūtai’s strength to 96 aircraft.

At the end of May, Shiden pilots managed to shoot down two B-29 bombers. During June, they also engaged long-range Mustang fighters over the Kantō area. In the final weeks of the war, Tsukuba Kōkūtai was relocated to Katori airbase in preparation for an anticipated enemy invasion. After the war, the three-story concrete building of the former Tsukuba Kōkūtai headquarters at the disbanded Tomobe base was used as a school and later as an administrative building for a hospital. In 2011, during hospital expansion and transformation into a mental health facility, space was freed up for a room dedicated to the history of Tsukuba Kōkūtai. In 2013, demolition of the original headquarters building was planned, but the same year a museum of the unit was instead established inside. In 2018, the museum moved to a neighboring building, and the original headquarters was declared a protected cultural monument by the city of Kasama. The exhibition, which commemorates the history of the base and Tsukuba Kōkūtai, includes a replica of a Zero fighter aircraft.