MACHINE PISTOL EVOLVEMENT. The Japanese Imperial Army Technical Department’s development plans initiated in 1920 included research into development of Jidoutaju, [automatic short guns]. Initial development commenced at the Tokyo Artillery Arsenal in 1924/25 under the direction of General Kijiro Nambu as head of the Small Arms Works. It would be many years of experimentation, development and rejection by a hesitant Japanese Government before recognition and acceptance of a machine pistol for unit service.

In the late 1930’s paratroop units were formed with guidance from their allied German paratrooper organizations. German emphasis was placed on the need for automatic weapon use by the air troops. In April 1939 General Nambu through his firm Chuo Kogyo K.K., submitted his third prototype machine pistol, [Type III, Model B] in 8 mm caliber to various Government entities. Although it was not considered totally satisfactory by the Infantry and other schools from testing it was accepted out of necessity and officially designated as Type 100. Two patterns were produced. One with a solid wood stock and one with a folding wood stock for paratroop use. They would be issued to both army and navy units. These are designated as Type 100/1 to separate them from a later pattern of Type 100 weapons put into production in 1944. The Nambu firm developed both patterns at Nagoya Arsenal’s Toriimatsu factory. For the paratroop pattern, a redesigned configuration provided a folding stock similar to the modifications made to the Type 38 carbine for paratroop issuance. The stock is separated behind the receiver and a hinged assembly attached with two locking pins on the left side. When released, the hinged stock swings to the right and snugs parallel to the receiver. The overall length is reduced by 476.25 mm [18.75 inches]. A lug fixture for bayonet attachment and bipod was also added to the basic design.

The Nambu firm as the sole manufacturer, started production of the guns in August 1942. They produced less than 200 of both patterns, [hinged and solid stock], before converting to limited production of a changed pattern in 1944 identified as Type 100/2. [Nagoya Army Arsenal was the only other producer of the Type 100/2 weapons with a total quantity recorded at 7250 by both manufacturers].

A body chest pack designed for use with the folding stock Type 100/1 contained the weapon, Type 30 bayonet, magazine and accessory canvas pouch for tools and spare parts. Magazines were carried in separate pouches.