Japanese Fighters in Defense of the Homeland, 1941–1944

Each district (plus Korea and Formosa) had its dedicated army command of the same name: Hokubu-gun Shireibu (Northern Army Command), Tobu-gun Shireibu (Eastern Army Command), Chubu-gun Shireibu (Central Army Command) and Seibu-gun Shireibu (Western Army Command). The army commands had operational control over their local land units, anti-aircraft forces and air defense fighter units of the Imperial Japanese Army Air Force (IJAAF). The commanding officer of the army command was at the same time the commandant of a military district. In this capacity he was responsible for implementing the orders from the Rikugunsho concerning the development of defense infrastructure and liaising with local civilian authorities. On the other hand, as a commanding officer of an army command the same individual reported directly to the Boei Soshireibu and was responsible for the defense of his district and the training of subordinate combat units. This dual tasking made coordination of defensive efforts and proper allocation of resources difficult. For example, all logistical issues were the domain of the Rikugunsho, while dislocation of military forces and the construction of fortifications were controlled by the Sanbo Honbu. In this context the Boei Soshireibu was in fact more of a coordinating body rather than a proper operational command.

Nakajima Ki-84 “102” was used as the prototype of the Ki-84 Hei variant armed with Ho-155 30 mm cannons, which never went into a full-scale production. Until the end of the war the Ki-84 was built in the Ko configuration in a addition to a small number of Otsu  models.

The Japanese air defense consisted of flying combat groups (hiko sentai1) and anti-aircraft artillery units (equipped mostly with Type 88 75 mm guns2) grouped into air defense brigades (boku ryodan). The air defense system was supplemented by military and civilian observation posts and very rudimentary Type Ko (A) radar stations3. In addition, the Navy provided a measure of early warning by deploying various types of auxiliary ships equipped with long-range radio sets some 950–1000 km (600 miles) east and south-east of Japan’s shores (so called picket boats). Among air defense areas of vital importance identified by Daihonei were Tokyo, Yokohama and Kawasaki in the Eastern Military District; Nagoya, Osaka and Kobe in the Central Military District; and industrial centers of Yawata and Kokura in northern Kyushu (Western Military District). The air defense units were dislocated in line with to those priorities.
Similarly to the land forces, the air command and control structure was rather complicated. Japan’s air force was not an independent service. While the Army and Navy both had their own aviation services, the forces lacked dedicated organic command. Air defense sentais were under operational control of army commands in respective military districts which ultimately extended to the Boei Soshireibu. However, administratively the units were subordinate to both the Rikugun Koku Sokanbu (Inspectorate General of Army Aviation), which controlled crew and combat training and to the Rikugun Koku Honbu (Army Air Head Office), which was responsible for all technical aspects of Army Air Force (including aircraft production, flight testing of new aircraft types, aircraft allocation to combat units and distribution of spare parts).

006 Japanese

When the war in the Pacific broke out on December 8, 1941 (Tokyo time) the commander-in-chief of the Eastern Army Command Chujo Shizuichi Tanaka (replaced on December 24 by Taisho Kotaro Nakamura) had at his disposal two fighter groups (5th and 144th Sentai) and the Tobu Boku Ryodan (Eastern Air Defense Brigade). The Central Army Command (commanded by Chujo Yoji Fuji) included the 13th Sentai and Chubu Boku Ryodan (Central Air Defense Brigade). The 4th Sentai and Seibu Boku Ryodan (Western Air Defense Brigade) were subordinate to the Western Army Command under the command of Chujo Keisuke Fujie. The air defense was augmented by 15 Mitsubishi Ki-15 reconnaissance aircraft from the 101st Dokuritsu Hiko Chutai (independent flying squadron) deployed to airfields in all three districts (Ki-15s were also fielded by the 4th and 13th Sentai). All air units were under administrative control of the 1st Hikoshudan (1st Flying Corps).
The Northern Military District and Korea did not see deployment of any air units as the Japanese tried hard not to provoke the Soviet Union. Besides, they considered those areas to be rather unlikely to come under attack, mainly due to the lack of high-value targets. Strategic installations in the area (army bases, airfields and ports) were defended by dedicated anti-aircraft artillery regiments (rentai) or battalions (daitai).
5th Sentai (CO Chusa Kenzo Onda) was based at Kashiwa in Chiba Prefecture, not far from Tokyo. In December 1941 part of the group was detached to Matsudo to bring the aircraft even closer to the nation’s capital. At the start of the hostilities the 5th Sentai had 25 Ki-27 aircraft in two hiko chutais (flying squadrons). 144th Sentai commanded by Shosa Shigechika Tomari was established in July 1941 at Chofu near Tokyo as a dedicated air defense unit. The group consisted of two flying squadrons and had 19 Ki-27 fighters on strength. 13th Sentai under the command of Chusa Takeo Tateyama had three flying squadrons (after incorporation in November of the 102nd Dokuritsu Chutai) and 37 Ki-27 aircraft. The group was based at Taisho near Osaka, but its two chutais were also detached to Itami in Hyogo Prefecture and to Kashiwa near Tokyo. 4th Sentai (CO Chusa Shuichi Okamoto) also consisted of three squadrons after it had merged with 103rd Dokuritsu Chutai4 in November. The 1st and 2nd Chutai equipped with 25 Ki-27 fighters based at Pingtung (Japanese: Heito) in Formosa and 12 Ki-27s belonging to the 3rd Chutai deployed to Gannosu in Fukuoka Prefecture (Kyushu). In January 1942 all squadrons of the 4th Sentai were moved to Ozuki in Yamaguchi Prefecture (western Honshu), while all chutais of the 13th Sentai found their new home at Taisho.

 Kawasaki Ki-61-I Ko Hien “16” (s/n unknown) was flown by Gunso Matsumi Nakano from Shinten Seiku-tai of the 244th Sentai (which is indicated by the red tailplane and lack of the group’s emblem), Chofu, February 1945. Victory marks under the cockpit indicate three B-29 kills – two downed in ramming attacks on December 3, 1944 and January 27, 1945 and one shot down in a conventional way. The white katakana Na inscription on the rudder is the first syllable of the pilot’s name. The aircraft has no antenna mast or fuselage-mounted machine guns.

At that time the Nakajima Ki-27 was the basic fighter type in the Army Air Force. Designed in 1936, the Ki-27 was an all-metal, cantilever low wing monoplane with a fully enclosed cockpit, fixed landing gear with a tail skid. The production of the Ki-27 Otsu began in 1939 and by the time the war began almost all older Ki-27 Ko aircraft in service with combat units had been replaced with the new variant. The aircraft mounted a pair of 89-Shiki (Type 89) 7.7 mm machine guns placed on each side of the fuselage between the engine and the cockpit. The fighter had a top speed of 470 km/h at 3500 m and could climb to 5000 m in 5 minutes, 22 seconds. It was a very nimble and agile machine, much liked by the pilots, but hardly a true interceptor, mainly due to its poor performance, inadequate armament and complete lack of cockpit or fuel tanks protection. […]


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Air Battles 21

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