Despite their far-reaching strategic and tactical advances in the early stages of World War 2, the Imperial Japanese Army was slow to advance on several technological fronts - one of these being the submachine gun. The British adopted their famous "Sten" while the Americans had their "Tommy Guns" and "Grease Guns" and the Germans perfected their MP38/MP40 series - even the Australians developed their own excellent "Owen" series. However, the only original Japanese submachine gun of note in the whole of the conflict was the "Type 100" series, the other SMGs used coming from procurement of foreign designs. Interestingly, the battlefield that was the jungle was prime ground for the use of such close-quarters weapons yet it would appear that Japanese authorities were content with their rifles, pistols, grenades and machine guns in their endeavor to seize Southeast Asia and the Pacific.
Finally realizing the value of the submachine gun in modern warfare, Japanese authorities finally moved on development of an indigenous submachine gun design. The Type 100 originated from an Imperial Japanese Army (IJA) requirement though it was not deemed a wholly important project at its outset, thusly it suffered from lack of attention, resources and development prior to frontline use. The task of developing the new firearm was given to the fabled Nambu Arms Manufacturing Company and preliminary designs were penciled, leading to prototypes being completed and subsequently tested. Since the Japanese lacked any formal experience in design and production of submachine guns, much was garnered from the procured foreign models that the IJA held in some number. The finalized IJA Type 100 incorporated several features from existing SMGs (including that of the German Bergman MP18 series to which it bore some resemblance) and was a design with similar qualities that would be cheap to manufacture in large numbers and require minimal training and field maintenance . It was not until 1942 that the first production-quality versions of the Type 100/40 (100 Shiki Kikan-tanju) were being delivered to the IJA for operational use and initial combat actions involving the weapon occurred during the Japanese amphibious assault landings against neighboring China - a land ripe with natural resources required by the growing power of Japan. Interestingly, these early versions were fielded with bayonet lugs and bipods. An estimated 10,000 of this initial batch were produced out of the Kokura Army Arsenal.
The Type 100 series was primarily characterized by its solid, all-wooden body that also made up the integrated grip and fixed stock. The internal metal components and barrel assembly were all laid within the wooden body which also extended forward to create a forend grip, protecting the users hand from the hot barrel. The barrel extended a short distance away from the receiver and was perforated to promote self-cooling. There was a nondescript muzzle and sights were set along the top of the receiver, these tilted to the left side of the gun body assuming the firer was right-handed. The thin trigger assembly was underslung ahead of the angled grip and protected within an equally thin trigger ring. Sling loops were located aft of the muzzle along the barrel right side and under the buttstock aft of the grip. The magazine was installed into a left-side mounted insert ahead of the gun's true center of balance.
The Type 100 held some inherently good qualities, chief of these being its rugged simplicity. It was relatively cheap to manufacture for its time and was rather utilitarian in its overall configuration, allowing for ease-of-use and ease of maintenance in-the-field. The Japanese were keen to produce a chrome-plated bore barrel to combat the corrosive effects of the jungle environment where moisture and mud were as a common an enemy as were the Australians, New Zealanders, Indians, British and Americans. The Type 100 was also set to automatic fire-only which allowed the gun to lay down considerable firepower in a short amount of time. The curved box magazine held 30 rounds of 8mm ammunition while the action was of blowback in design while being air-cooled. Muzzle velocity was 1,100 feet per second with a rate-of-fire of 450 rounds per minute and the low recoil made it very handy in confined spaces. Weight was a manageable 8.4lbs and a shoulder sling could be outfitted for transporting on long marches through the jungle.
However, the Type 100 also held several inherent design disadvantagess that kept it from ever really becoming as well-respected as her contemporaries. The Type 100's design was centered around the 8x22mm Nambu cartridge which was nothing more than the Nambu pistol round- a cartridge well known for its low-powered performance and general ineffectiveness at range. This is not to say that the round lacked man-stopping capabilities but there were other more interesting options then-available including the Bergman MP18's original 9x19mm Parabellum round. Sights were tilted towards the left side of the receiver which was rather awkward in practice, especially for left-handed firers. The Type 100 also utilized a side-mounted magazine feed which made handling of the weapon somewhat cumbersome - especially in confined spaces. Additionally, the automatic fire-only mode meant that overall accuracy could suffer and 30 rounds of ammunition could be burned through in a matter of seconds. The ammunition feed was also prone to jamming in the field due to the complexity nature of its design and poor ammunition quality. The Type 100's initial rate of fire of 450 rounds per minute was quite low and the bayonet and bipod were hardly practical for a submachine gun. All told, the Type 100 was a serviceable SMG but much work still lay ahead to perfect weapon.
In 1944, the Type 100/40 was revised to help offset some of the earlier complaints producing the "Type 100/44" designation. The rate-of-fire was increased to 800 rounds per minute and general reliability was improved for field use based on operational feedback. Production was further simplified to coincide with deteriorating Japanese war resources (hence the Type 100/44 sometimes being referred to as the "simplified" Type 100). The length of the barrel was increased slightly and the sights were simplified by being fixed into position while the relatively useless bayonet fittings and bipod were dropped altogether - though the bayonet was still an integral part of the Type 100's design, though now affixed to the barrel itself. About 8,000 examples of this version were completed out of the Nagoya Army Arsenal. Specialized development also produced a "paratrooper-friendly" variant complete with a folding stock for a smaller profile and lightened operating weight. An estimated 6,000 to 7,500 were produced in all out of the Nagoya Army Arsenal.
By early 1945, the Japanese war machine was incurring heavy losses. Daily Allied bombing raids would eventually reach the heart of Japanese manufacturing and curtail much of the power that the IJA enjoyed in the early phases of the war. Dwindling production and lack of suitable resources ensured that the mighty Japanese military would soon be "starved" into submission. As such, many products were hastily pieced together and sent out of factories without thorough completeness and quality control, leading to some very rough weapons being fielded out of desperation. The Type 100 was one such end-product and, by the end of the war in August of 1945, production of the submachine gun totaled under 30,000 - hardly enough to made an imprint in the defensive war Japan was eventually faced with. Despite the improvements, the Type 100 never materialized as a war-winning effort though - from those lucky enough to have been issued it - it proved a hardy system worthy of the Japanese infantryman. Beyond the war, the Type 100 still saw active combat service with the Chinese and North Korean armies during the Korean War (1950-1953) as well as with elements of the North Vietnamese Army during the 1st Indochina War (1946-1954). Some could also be found in regional conflicts thereafter - albeit to a limited extent.