The Mitsubishi J2M Raiden (Thunderbolt), Allied codename Jack, was a land-based interceptor of the Imperial Japanese Navy, designed for speed and climb to counter high-altitude bombers.
Origins and Development
Specification
In 1939, the Imperial Japanese Navy issued the 14-Shi specification for a local-defence interceptor.
Unlike the long-range, manoeuvrable A6M Zero, this fighter was to emphasise speed, climb rate, and heavy armament.
Designer
Jirō Horikoshi, also responsible for the A6M Zero, led the project at Mitsubishi.
First Flight
The prototype J2M1 flew on 20 March 1942.
It featured the powerful Mitsubishi Kasei 13 radial engine with an extension shaft and cooling fan.
However, engine overheating, poor cockpit visibility, and landing gear issues delayed acceptance.
Operational History
Introduction
The type entered service in December 1942, but early reliability problems limited deployment.
Role
The Raiden was conceived as a point-defence interceptor, particularly against B-29 Superfortress raids on the Japanese home islands.
Combat Use
From 1944 onward, J2Ms equipped units defending Kyushu, Honshu, and Okinawa.
Pilots valued its climb and firepower but criticised its handling and limited high-altitude performance compared to Allied fighters.
Production
Approximately 621 aircraft were built before Japan’s surrender in 1945.
Variants
J2M1 Prototype
Engine
Mitsubishi MK4C Kasei 13 (1,430 hp).
Armament
Two 7.7 mm machine guns and two 20 mm cannons.
Problems with cooling and visibility prevented production.
J2M2 Model 11
First production version (1943).
Engine
Mitsubishi MK4R-A Kasei 23a (1,800 hp) with mechanical supercharger.
Armament
Two 7.7 mm machine guns (fuselage) and two 20 mm Type 99 cannons (wings).
Early service was plagued by engine troubles.
J2M3 Model 21
Most produced variant.
Armament
Four 20 mm Type 99 cannons (two in the fuselage, two in the wings).
Improved canopy and systems.
Mainstay of home-defence units against B-29s.
J2M4 Model 32
Experimental high-altitude version.
Engine
Kasei 23c with turbo-supercharger.
Persistent reliability issues; very few built.
J2M5 Model 33
Engine
Kasei 26a with a mechanically driven supercharger.
Armament
Four 20 mm cannons.
Improved high-altitude performance but produced in small numbers.
J2M6 Model 31
Based on the J2M3 with a redesigned canopy for better visibility.
Limited production.
J2M7 Model 23
Planned high-altitude interceptor with turbo-supercharged Kasei 26a.
Only prototypes were completed before war’s end.
Assessment
Strengths
Excellent climb rate, heavy armament, rugged construction.
Weaknesses
Poor cockpit visibility, limited manoeuvrability, unreliable engines, and inadequate high-altitude performance against B-29s.
Legacy
Though overshadowed by the Zero, the Raiden was one of the few Japanese fighters purpose-built as an interceptor.
Its design reflected Japan’s late-war shift towards homeland defence.
In summary
The Mitsubishi J2M Raiden was a specialised interceptor, produced in modest numbers, that fought primarily in defence of Japan from 1943 to 1945.
Despite technical flaws, it remains significant as Japan’s only dedicated naval interceptor of the war, with variants ranging from the troubled J2M1 prototype to the improved but scarce J2M7.
