Kashima Naval Air Group

The Kashima Naval Air Group (鹿島海軍航空隊) was a seaplane training unit of the Imperial Japanese Navy, established on December 15, 1938, at Oyama on the southern shore of Lake Kasumigaura (present-day Miho Village, Inashiki District, Ibaraki Prefecture). It was placed under the Yokosuka Naval District as a permanent practice air group (練習航空隊), inheriting the seaplane training mission from the Kasumigaura Naval Air Group whose facilities were being reallocated for Yokaren (Naval Aviator Preparatory Course) training. Planning began around 1937, initially under the name Annaka Air Group.

The air group trained pilots on the Nakajima E8N (Type 95 Reconnaissance Seaplane), Mitsubishi F1M (Type 0 Observation Seaplane), and Aichi E13A (Type 0 Reconnaissance Seaplane), using catapult training platforms and lakeside slipways; Japanese sources also list the Type 2 floatplane fighter and the Zuiun reconnaissance seaplane. By December 1941, it had expanded to over 1,000 personnel with more than 100 aircraft. Nine commanders served between 1938 and 1945.

During the Pacific War, as fuel and aircraft shortages curtailed training, the unit's role broadened to include anti-submarine patrols over the Kashima Sea (鹿島灘) and homeland air defense operations. The 631st Naval Air Group, flying Zuiun, was formed here in December 1944 and moved elsewhere the following January. In 1945, the unit formed the 2nd Sakigake-tai special attack squadron; on May 11, 1945, five members flew two seaplanes from Ibusuki Air Base on a tokko mission against Allied ships off Okinawa. None returned. The air group was disbanded following Japan's surrender on August 15, 1945.

After the war part of the base served from 1946 to 1997 as the Kasumigaura branch hospital of Tokyo Medical and Dental University, which is why the headquarters and other buildings survived. Miho Village acquired about 4.3 hectares in 2016 and opened the site to the public on July 22, 2023. The headquarters building, garage, boiler house and catapult foundations remain, making it one of the few former naval air group sites in Japan that still retains a group of original buildings.