Hyakuri Naval Air Base (Hyakuri Air Base & Yuhien Park)
百里原海軍航空隊（百里基地・雄飛園）
Imperial Japanese Navy air training base established in 1938 in Ibaraki Prefecture. Hyakurihara Naval Air Group began as a primary flight-training unit, added carrier attack and dive bomber training from late 1943, and in the war's final months formed special attack (kamikaze) units that flew sorties during the Battle of Okinawa. Now home to JASDF Hyakuri Air Base — the closest fighter base to Tokyo — with the Yuhien outdoor memorial park displaying retired military aircraft and monuments to the fallen.
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History
Hyakurihara Naval Air Group (百里原海軍航空隊) was established on December 15, 1938, as a detachment of the Tsukuba Naval Air Group on the Hyakuri Plateau in what is now Omitama City, Ibaraki Prefecture. The land was requisitioned from local farmers for the construction of an airfield dedicated to training naval aviation personnel.
The base at first served as a primary flight training facility. About one year after its founding, on December 1, 1939, the detachment was elevated to an independent naval air group. Familiarization courses on operational aircraft were added later, with trainees learning to handle the Type 97 carrier attack bomber (Nakajima B5N) and the Type 99 carrier dive bomber (Aichi D3A).
From around December 1943, the base expanded its mission to include familiarization training on carrier dive bombers and attack aircraft, as well as land-based attack bombers. From about June 1944, Hyakurihara was additionally assigned patrol duties over the Pacific approaches to the Japanese homeland.
In the war's desperate final months, Hyakurihara Naval Air Group formed special attack (tokko) units for kamikaze operations during the Battle of Okinawa. Type 97 carrier attack bombers of its Tokiwa-Chūka, Kōka and Seiki units flew five sorties from Kushira Air Base between April 12 and May 12, 1945 (about 14 aircraft in published unit lists). Type 99 carrier dive bombers of its four Seitō units flew four sorties from Kokubu between April 6 and June 3, 1945 (about 24 aircraft). In the war's final week, Suisei (Yokosuka D4Y) dive bombers sortied from Hyakurihara against the Allied fleet. The number of men from the air group who died in special attack operations is given as about 85, a figure not confirmed in the sources consulted.
After Japan's surrender in August 1945, the airfield was dismantled and the land returned to settlers and repatriates for agricultural use. The site remained farmland until 1956, when construction of a Japan Air Self-Defense Force base was planned; amid local opposition and the long-running Hyakuri Base lawsuit, Hyakuri Air Base was established in 1966.
Today, JASDF Hyakuri Air Base is the closest fighter base to Tokyo, approximately 80 km northeast of the capital. The base's Yuhien (雄飛園) outdoor memorial park, located near the main gate, is open to the public on set days. It displays retired JASDF aircraft — including F-4EJ Kai, RF-4E, F-86D, F-86F, F-104J, F-1, T-2 Blue Impulse, and T-33A — along with stone monuments erected in 1976 commemorating the wartime naval aviators who gave their lives. Cherry trees planted around the monuments honor the memory of the special attack crew members and all others who died in service at Hyakurihara.