The Nakajima B5N1 carrier based Torpedo Bomber (Kate) was designed in 1935 by a Nakajima design team under the supervision of Katsuji Nakamura and went into production as the Navy Type 97 Model 1 attack bomber in 1937. It was soon discovered that it was extremely venerable to any modern fighter aircraft so by 1939 the B5N2 was designed and put into production. By the outbreak of the war even the B5N2 was considered obsolete, yet still an effective torpedo attack aircraft.
The B5N1 Type 97 was powered by a 9 cylinder single row 770hp Nakajima Hikari 3 radial engine. The B5N2, produced from 1939 onward, was powered by the twin row, 14 cylinder 1000hp Nakajima Sakae 21 radial engine which was longer and smaller in diameter.
There were 1,150 B5N1 and B5N2 Torpedo Bombers produced during the war. The B5N had an operational range of 610 miles (fully loaded) and could carry a single torpedo or three 250 pound bombs. It was a highly maneuverable aircraft with good range and an adequate payload carrying capacity but it had no crew armor nor self sealing fuel tanks and its only defense was twin rear mounted 7.7 mm (30 cal) machine guns.
The B5N2 Torpedo Bomber was used effectively against the American pacific fleet at Pearl Harbor where 144 B5N2 Kates were in the attacking force. The B5N2 is also credited with sinking the Carriers USS Lexington, USS Hornet, and USS Yorktown
By 1944 the B5N2 had been replaced by the Nakajima B6N (Jill) Carrier based torpedo bomber but a few B5N2s stayed in service until the end of the war as trainers, target tow aircraft, and those that remained in flying condition were used as Kamikaze aircraft in 1945.