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Developed from the powerful N1K1 Kyofu (Mighty Wind) floatplane fighter, the N1K1-J Shinden (Allied codename George) turned out to be one of the finest Japanese fighters of the war, and soon proved to be the equal of any Allied Fighter Aircraft in the Pacific Theatre.

Kawanishi Kokuki KK commenced work on a landplane adaptation of the floatplane in August 1942 as a private venture to meet the J.N.A.F. requirement for an interceptor fighter to be used from land bases. The first prototype, bearing the designation Model X-1 Shiden, and powered by a massive 1,880hp Nakajima NK9B Homare 11 18-cylinder radial engine made its maiden flight in 27 December 1942, This was followed by three further prototypes, completed before July 1943, utilized the 1,990hp Nakajima NK9H Homare 21 engine, but even before these commenced flight trials the Imperial Japanese Navy placed an order for the aircraft directly from the drawing board. Flight trials soon revealed that the aircraft had outstanding maneuverability characteristic, and a further five prototypes were subsequently constructed concurrently with the first production machines for further testing.

A unique feature of the Shinden was the automatic flaps which automatically altered their angle with changes in the g force during manoeuvres, thus supplying additional surface when a high lift coefficient was required. Unfortunately for its Japanese Navy pilots, who began to evaluate the type in July 1943, the Nakajima engine, which had been placed in production before adequately finishing its testing programme, proved unreliable with numerous teething problems. In addition, the mid-wing configuration was found to restrict the pilot’s visibility and the wheel brakes were so bad that pilots would often land on the rough ground alongside a runway in order to reduce the length of the landing run. The worst feature of all however, was the telescopic retractable undercarriage which the design team had developed to permit the use of an airscrew of sufficient diameter to make maximum use of the engine’s available power. The mid-wing configuration of the aircraft meant that undercarriage legs of exceptional length had to be utilized. The designers thought that they had solved the problem of allowing the undercarriage to be stowed in the wings by using a system of double retraction, in which the legs of the landing gear could be lowered and then extended for landings, or contracted and folded into the wing wells during flight. The system however proved highly fragile and in use would regularly collapse under even moderate side loads. In fact, such was the rapidity that the new fighter had been rushed into production that insufficient time had been allowed to iron out the teething troubles that soon became apparent in production machines, resulting in the production lines constantly having to be modified to effect the modifications dictated by the flight testing of the prototypes.

Production was initiated by Kawanishi at its Naruo factory, building seventy N1K1-J Type B fighters from July 1943 until the end of 1943, and a further 485 by December 1944 when the factory changed over to the manufacture of the improved Shiden-Kai. Others were built at the Himejo works from December 1943 (with one aircraft being completed in 1943 followed by 467 more in the following year-Production coming to an end as a consequence of US bombing of the factory). Thus a total of 1,007 N1K1-J fighters, including prototypes were built. Three basic models of the N1K1-J Shiden fighter were built, these differing principally in the arrangement of the armament. The original N1K1-Js had two 7.7mm machine-guns in the fuselage, two 20mm cannon in the wings and two more 20mm cannon suspended in under-wing gondolas; The N1K1-Ja had the fuselage machine guns deleted and a new wing provided that could house all four cannon; and finally the N1K1-Jb with a redesigned square tipped vertical tail surface. Another later modification was the fitting of six rocket powered bombs on a rack beneath the fuselage. One Shiden was trialed in 1944 with a supplementary rocket boost unit- Trials with this proved encouraging and a few other machines would be similarly equipped, although none were actually employed operationally.

The N1K1-J became operational with the J.N.A.F. early in 1944 and, despite the troubles with the Homore engine, soon proved to be a redoubtable warplane even in the hands of a moderately trained pilot, with its pilots even coming to see the formidable Grumman Hellcat as a relatively easy “kill”. The first Shiden unit in action against the Americans was the 341st Air Corps which arrived at Luzon from Formosa on October 20, 1944 as a part of the 2nd Air Fleet. The Shiden was again met in large numbers during the invasion of Okinawa and continued to be encountered frequently thereafter until the end of the war. Some were expended on Kamikaze attacks but plans to build a specially modified version intended specifically for suicide attacks failed to materialize.

The problems that had plagued the development of the N1K1-J led to the Kawanishi designers proposing a new fighter which would benefit from the lessons learned. This became the much improved N1K2-J Shiden-Kai, undoubtedly the J.N.A.F.’s finest production fighter throughout the war. The N1K2-J differed from the earlier N1K1-J in having a low wing configuration and a new tail, whilst retaining the original powerplant. In addition the fuselage was lengthen substantially and refined, the contours of the engine cowling were improved, Emphasis is placed on simplification of production,-in total, excluding nuts and bolts, only 43,000 component parts were employed in the building of a N1K2-J compared to some 66,000 components of the original Shiden. Like its predecessor, the N1K2-J was ordered by the Navy straight off of the drawing board. Production however proceeded rapidly thanks to the reassignment of personnel released from the manufacture of the N1K1-J and the abandoned J6K1 Jimpu project.

The prototype of the NIK2-J made its first flight on the 31st December 1943, and was immediately accepted by the J.N.A.F. as the Shiden-Kai 21. At the Narau plant a further seven prototypes would follow by June 1944, although, as before this was concurrent with the tooling up and building of the first production machines, this resulted in unnecessary confusion and delay. The situation was worsened by a number of teething troubles which proved difficult to eliminate. In addition American bombing by B-29 Superfortresses would result in shortages of Homare engines, steel forgings, aluminium extrusions, landing gear etc. Thus only sixty Shiden-Kais were completed by the Naruo plant between July 1944 and the end of the year, and only 294 subsequently. Building of the Shiden-Kai was also undertaken at the Himeji plant from March 1945 (44 machines completed); at Mitsubishi’s 7th Airframe plant (nine built fro March-August 1945); at Aichi’s Ettoku plant (one machine completed in July 1945); at Showa’s Shinonoi plant (one machine completed in August 1945); and at the Naval Air Arsenals at Hiro (1), Omura (10) and Atsugi (none completed before the war came to an end).

The Shiden-Kai entered service in May 1944 and soon established itself as the best all-round fighter operational in the Pacific. On one occasion, a Shiden 21 flown by Flight Warrant Officer Kinsuke Muto successfully destroyed four out of twelve Grumman Hellcats before the others broke off the combat and fled back to their carrier.

A small number of machines were completed as N1K2-K Shiden-Rensen two seat dual control fighters, and a number of improved variants were in the process of being either in prototype form or on the drawing board when the war came to an end (NIK3-J with the engine moved six inches forward to improve the centre of gravity and the addition of two additional 13.2mm type 3 machine guns in the fuselage; N1K3-A proposed shipboard version; NIK4-J powered by a fuel injected 2,000hp NK9H-S Homare- 23 engine ; N1K4-A Shipboard version of N1K4-J; and N1K5-J high altitude B-29 Superfortress interceptor powered by a 2,200hp Mitsubishi MK9A engine).