[1] In 1935, officers in the Imperial Japanese Navy began to investigate 20 mm automatic cannon as armament for future fighter aircraft.

These all shared the same operating principle, the advanced primer ignition blowback mechanism pioneered by the Becker cannon, but fired different ammunition: 20×72RB, 20×101RB, and 20×110RB, respectively.

To produce the Oerlikon guns, a group of retired Navy admirals created a new arms manufacturing company, the Dai Nihon Heiki KK.

Towards the end of the war it developed a preference for installing the Type 99 Mark 2, presumably to counter the improving performance and ruggedness of US combat aircraft.

The fixed installation was developed first, as a fighter gun fed by a 60-round drum magazine, mounted in the wings of the famous Mitsubishi A6M Zeke or Zero.

A flexible version, initially developed for the Mitsubishi G3M bomber, was inverted to put the ammunition drum below the line of sight of the gunner.

A more practical solution was provided by the Type 99 Mark 1 Fixed Model 4, which featured a Kawamura-developed belt feed mechanism.