Japanese Type 10 and Type 89 Grenade Launchers: Evolving the Light Close Support Weapon Concept
Introduction
During the interwar period, the Japanese army created one of the most original and successful designs weapons The Type 10 and Type 89, known as the Type 10 and Type 89, were close infantry support weapons. These systems occupied a middle ground between a hand grenade and a light mortar, capable of engaging targets inaccessible to conventional small arms while remaining light enough to be carried by a single soldier. During World War II, grenade launchers became a characteristic feature of the Japanese infantry, earning the respect of their opponents, and their concept influenced the development of similar weapons in other countries.
Prerequisites of creation
The problem of providing infantry with fire at distances between the throwing range of a hand grenade and the minimum effective range artillery This became evident during World War I. When enemy forward positions approached within 200 meters, artillery often ceased fire for fear of injuring its own troops. This created a dangerous gap between the throwing distance of a grenade—approximately 20–30 meters—and the effective support range of field artillery.
The Japanese army's interest in such weapons dates back to the Siberian Intervention of 1918–1922. A specially designed grenade launcher and rifle grenade were developed, but the system proved cumbersome and was not widely adopted. Subsequently, attention focused on creating a simpler device capable of throwing a grenade a distance of approximately 200 meters while being light enough for infantrymen to carry at all times.
Left: Model Ko grenade launcher based on the Murata rifle; right: Model Otsu grenade launcher based on the Arisaka rifle. Source: US Army Artillery Museum
Work continued for about three years and culminated in the acceptance of the new weapon, initially simply called the "grenade launcher" (Tekidantō), into service on May 3, 1921. It was only in January 1922 that the designation "Type 10" was added to the name, based on the last two digits of the year of adoption according to the Japanese calendar (the 10th year of the Taishō era, 1921).
The Type 10 was initially designed to augment infantry fire at ranges beyond the reach of hand grenades, and was primarily intended to fire high-explosive fragmentation grenades. A wide range of special ammunition, including smoke, signal, and illumination, was also developed for it. Subsequently, after the adoption of the more advanced Type 89, Type 10 grenade launchers were increasingly used specifically for launching special ammunition and as an auxiliary means of communication and signaling.
Type 10 grenade launcher
The Type 10 was an extremely simple design. It consisted of a 50mm smoothbore barrel, a connecting rod housing the trigger mechanism, and a small curved base plate.
The weapon's overall length was approximately 508 mm, its barrel length was 241 mm, and its weight was approximately 2,5 kg. Its light weight allowed the grenade launcher to be carried with one hand, which markedly distinguished it from mortars of the time. Japanese authors have repeatedly noted that virtually no other weapon system in the world offered a comparable combination of lightness and firepower.
Grenade launcher Type 10. General appearance: A) assembled grenade launcher; B) grenade launcher in the stowed position; C) disassembled grenade launcher. Explication of parts: 1 - barrel; 2 - gas port; 3 - threaded section of the tube for the gas regulator; 4 - mainspring guide rod; 5 - striker; 6 - mainspring; 7 - firing pin; 8 - mainspring feeder; 9 - locking lug; 10 - split bushing; 11 - trigger; 12 - trigger axis; 13 - lock ring; 14 - trigger lever; 15 - coupling sleeve; 16 - base bushing latch; 17 - base plate rod base bushing; 18 - muzzle cap; 19 — base plate spring latch; 20 — base plate; 21 — rod connecting the base plate to the barrel. Source: Japanese Infantry Weapons / Intelligence Directorate of the General Staff of the Red Army. — Moscow: Voenizdat, 1945.
The Type 10 had a smoothbore barrel. Firing was carried out at a constant elevation angle of 45°, and range adjustment was accomplished in an unusual manner. The lower part of the barrel contained a gas vent connected to a rotary regulator. By varying the opening of the vent, the crew controlled the amount of propellant gases used to propel the grenade, thereby changing the firing range.
This solution was extremely simple and technologically advanced. The soldier didn't need to adjust the weapon's elevation angle or use complex sighting devices. All he had to do was set the regulator to the desired value and hold the grenade launcher at a standard angle.
To fire, the grenade was lowered into the barrel from the muzzle. After pulling the trigger, the striker fired, piercing the propellant cap located at the base of the grenade.
Type 10 grenade launcher from the collection of the Federal State Budgetary Institution Central Military District of the Russian Federation. Source: State Catalogue
Despite its simple design, the Type 10 had a number of drawbacks. The use of conventional hand grenades, which lacked stabilization and did not fit tightly into the barrel, limited the range and accuracy of fire. The maximum range, depending on the ammunition type, ranged from 160 to 220 meters.
Nevertheless, the grenade launcher proved to be a very useful weapon. It could hit targets hidden in trenches, behind folds in the terrain, and behind the walls of buildings, as well as provide signals and battlefield illumination. High-explosive, smoke, illumination, signal, and chemical ammunition were developed for it. In addition to special rounds, it could fire Type 10 and later Type 91 hand grenades.
During its service life, the design was modernized several times. Changes were made in 1924, 1929, and 1933, but the weapon's basic design remained unchanged.
Requirements for a new grenade launcher emerged
By the late 1920s, the Japanese Army had concluded that the Type 10's capabilities were no longer sufficient. Its firing range of approximately 200 meters no longer met infantry requirements, and the use of conventional hand grenades limited the weapon's effectiveness.
The decision was made to develop a new system capable of engaging targets at ranges of over 600 meters. At the same time, the weapon had to retain the compactness and light weight of its predecessor.
The main problem was creating a new ammunition. The hand grenade was poorly suited for firing from a grenade launcher: its aerodynamic properties were unsatisfactory, and the lack of spin impaired accuracy. Therefore, Japanese engineers decided to switch to a special projectile with a driving band and a rifled barrel.
Left: Type 10 grenade launcher; Right: Type 89 grenade launcher. Source: 小銃拳銃機関銃入門
The development of the new weapon took about seven years. On April 3, 1930, it was officially accepted into service under the designation "Type 89 Heavy Grenade Launcher" (named after the long timeline from the founding of the empire, where 1929 is the year 2589).
The designation "heavy" didn't imply that it belonged to the heavy weapons category. It was introduced merely to distinguish the new model from the lighter Type 10. In practice, the Type 89 remained an exceptionally compact weapon: it weighed only 4,7 kg and could be carried in a backpack or strapped to the back.
Design of the Type 89 grenade launcher
Externally, the Type 89 resembled its predecessor and also consisted of three main parts: the barrel, the tubular rod with the firing mechanism, and the base plate. However, the internal design was more complex.
The main difference was the rifled barrel. Its bore contained eight right-hand grooves, imparting spin to the projectile. This dramatically increased accuracy and allowed the use of more advanced ammunition.
Schematic representation of the Type 89 grenade launcher. Source: Weapons of the Japanese Infantry, Intelligence Directorate of the General Staff of the Red Army. — Moscow: Voenizdat, 1945.
Another important feature was the original range-variation system. Unlike the Type 10, which regulated the release of propellant gases, the Type 89 varied the chamber volume under the projectile. This was accomplished using a rotating drum connected to a worm gear. As it rotated, the firing pin and its housing moved up or down within the barrel, changing the volume of space in which the propellant gases expanded after ignition.
The larger the chamber volume, the lower the gas pressure and the shorter the firing range. This solution ensured smoother adjustment and increased repeatability.
Type 89 grenade launcher from the VIMAIViVS collection. Source: State Catalog
The grenade launcher rod had two scales: one was intended for firing the Type 89 grenade and covered distances from 120 to 650 m, the other was used when firing the Type 91 grenade and had divisions from 40 to 190 m.
Azimuth guidance was performed along a longitudinal line marked on the top of the barrel. A 45° elevation angle was typically used for firing, considered optimal and ensuring maximum range. Some grenade launchers were equipped with bubble levels or pendulum angle meters, but many models lacked such devices, and the elevation angle was determined visually. If necessary, the weapon could be used at lower elevation angles; Japanese manuals included firing tables for 25° and 15°, which reduced projectile flight time and lateral drift, although this reduced the maximum range.
Top: Firing a grenade launcher from a prone position; Bottom: Firing a grenade launcher from a kneeling position. Source: 諸兵射撃教範第二部問答研究
It was the combination of its relatively long range, light weight, and high rate of fire that made the Type 89 one of the most effective close-support weapons for Japanese infantry. Its maximum firing range was 650–670 meters, and its practical rate of fire reached 20–30 rounds per minute.
Ammunition
Simultaneously with the adoption of the Type 89, a whole line of specialized ammunition was developed. The most important of these was the Type 89 high-explosive grenade, which was fundamentally different from the hand grenades used with the Type 10.
The grenade weighed approximately 800 grams, of which approximately 150 grams was the explosive charge. Cast TNT of relatively low quality is usually specified as the bursting charge, although literature also contains reports of the use of surrogate TNT mixtures with more powerful or scarce components, including hexogen and picric acid. Unlike previous-generation grenades, the Type 89 was designed primarily as an offensive munition. Its casing had relatively thin walls, and its primary destructive effect was provided by the blast wave. However, tests conducted in 1945 at the American proving grounds in Aberdeen showed that the grenade produced hundreds of fragments upon detonation.
Left: Type 91 grenade with ejector tail; right: Type 89 grenade launcher projectile. Source: Gary Ormsby Collection
The design of the grenade's base was particularly interesting. A copper driving band surrounded the propellant chamber, covering a series of holes. After ignition, the propellant gases inflated the band, which engaged the barrel's rifling, simultaneously sealing the bore and rotating the projectile. Some of the gases escaped through the holes in the base, imparting forward motion to the grenade.
This solution was quite original. Unlike traditional mortars, where the propellant charge was located outside the mine, Japanese engineers placed it directly within the munition. This simplified the weapon's design and ensured high reliability.
Incendiary grenade. Source: Weapons of the Japanese Infantry, Intelligence Directorate of the General Staff of the Red Army. Moscow: Voenizdat, 1945.
In addition to the Type 89 high-explosive grenade, there were smoke, incendiary, signal, and illumination rounds. The Type 95 smoke grenade used a timer with a timer setting from 0 to 20 seconds. The Type 89 incendiary grenade contained approximately 300 grams of an incendiary mixture based on potassium nitrate, aluminum, and sulfur. Illumination and signal rounds were also produced in various colors.
Despite the introduction of specialized ammunition, the Type 89 retained the ability to fire the Type 91 hand grenade. The latter was a versatile munition that could be thrown by hand, launched from a grenade launcher, or used as a rifle grenade after attaching a tail fin. For firing from grenade launchers, a small propellant charge was screwed into the base of the grenade launcher.
However, due to the lack of interaction with the barrel rifling, the Type 91's effectiveness was lower than that of the dedicated Type 89 grenade. Its maximum firing range was approximately 190 m, and its accuracy was inferior to that of the dedicated ammunition.
Experimental smoke grenade. Source: 小銃拳銃機関銃入門
Interestingly, the story The development of ammunition for the Type 89 did not end with the completion of standard high-explosive fragmentation and smoke rounds. During the war, work was underway on shaped-charge ammunition, designated "Ta-type rounds" (タ弾). According to Jiro Sayama, two variants were developed—Type 2, the "Ko" variant, and the "Otsu" variant. The first weighed approximately 835 g, the second approximately 755 g. Despite their relatively small size, they were capable of penetrating steel armor approximately 50 mm and 55 mm thick, respectively. Although these rounds apparently never saw widespread use, their very existence demonstrates the significant potential of the Japanese grenade launcher.
Combat application
The Type 89 entered mass production with some delay, but the events of the early 1930s quickly proved its worth. By the Manchurian Incident of 1931, the grenade launcher was widely used by the Japanese army and received high praise.
Japanese sources cite a typical example. Chinese units sheltering in villages often continued to resist under rifle and machine gun fire. However, after several Type 89 grenade hits, accompanied by loud explosions, the defenders often abandoned their positions.
The Japanese 81st Guards Unit conducts amphibious landing exercises at Cam Ranh Bay, Vietnam, 1941. Source: medium.com
The grenade launcher later became the standard weapon of the infantry platoon. A platoon typically had a squad of three or four grenade launchers. The crews' primary mission was to suppress machine gun positions, destroy enemy positions in trenches and folds in the terrain, and support attacking infantry.
American troops who encountered the Type 89 in the Pacific quickly appreciated its effectiveness. U.S. Army and Marine Corps documents referred to it as the "knee mortar." This name was a misnomer, derived from the distinctive curved base plate. Some American soldiers believed the weapon was intended to be fired from the thigh or knee.
An American soldier with a captured Japanese Type 89 grenade launcher in Buna, New Guinea. Source: life.time.com.
There's a well-known case on Guadalcanal where a Marine attempted to fire a grenade launcher in a similar manner and suffered a severe leg fracture. In reality, the grenade launcher was always placed on the ground or some other solid support.
Despite its curious nickname, Americans held this weapon in the highest regard. Many veterans of the Guadalcanal campaign stated after the war that the US Army needed its own equivalent of the Japanese grenade launcher.
Production and place in the weapons system
After the outbreak of war in China, the importance of the Type 89 increased dramatically. While production was initially relatively small, it rapidly increased from the late 1930s onward. Production was carried out by arsenals in Nagoya, Osaka, and Kokura, as well as numerous subcontractors.
By the start of the Pacific War, the grenade launcher had become one of the most important weapons in Japanese infantry service. Each rifle platoon had a dedicated grenade launcher squad.
Soldiers demonstrate the use of a Type 10 grenade launcher during pre-war maneuvers. Source: Rikugun: Volume 2 — Weapons of the Imperial Japanese Army & Navy Ground Forces
Tellingly, in documents from the end of the war, grenade launchers are among the few weapons with which Japanese units were almost fully equipped. In one unit surveyed after the surrender, despite a serious shortage of rifles and artillery, grenade launchers were available in almost full strength—158 units per regiment. This indicates that the Japanese command attached extraordinary importance to them.
Experimental developments and Type 100
The success of the Type 89 didn't mean the end of further development. As early as the mid-1930s, there was a demand for a grenade launcher with a longer firing range. Research began on tail-mounted ammunition that would combine long range with good accuracy.
Type 100 experimental grenade launcher. Source: 小銃拳銃機関銃入門
The work resulted in the creation of a prototype grenade launcher known as the Type 100. Its weight was approximately the same as the Type 89, and its maximum firing range reached 800 m.
Special fin-stabilized grenades, designated "Type 2," were developed for it. They weighed approximately 800 g and were 214 mm long. Experiments were conducted with varying numbers of stabilizers, and the fuses and sighting devices were improved.
Cross-section of the experimental Type 2 finned grenade. Source: 小銃拳銃機関銃入門
By 1942–1943, the weapon had generally reached operational condition. However, the situation at the front no longer required new models, but rather mass production of existing weapons. As a result, the Type 100 was never accepted into service.
Bougainville rifle-grenade launcher
One of the most unusual episodes in the history of Japanese grenade launchers was the appearance of an improvised rifle-grenade launcher on the island of Bougainville.
In the summer of 1945, Australian troops captured several unusual weapons. These were Type 38 rifles with the front end of a Type 89 grenade launcher welded to their shortened barrels. The base plate was removed, and the rifle barrel was partially inserted into the grenade launcher.
A drawing of an improvised rifle-grenade launcher constructed from a Type 89 heavy grenade launcher and a Type 38 6,5mm infantry rifle. Australian forces captured seven of these improvised rifle-grenade launchers on Bougainville Island in July 1945. Source: 2nd Australian Corps Intelligence War Diaries, July–September 1945
According to a Japanese prisoner of war, the development of such weapons was due to the climate of Bougainville. The high humidity caused the propelling charges of the Type 89 grenades to malfunction. However, the fuses and explosive charges continued to function.
A drawing of an improvised rifle-grenade launcher constructed from a Type 89 heavy grenade launcher and a Type 99 7,7mm infantry rifle. Australian troops captured one such improvised rifle-grenade launcher on Bougainville Island in July 1945. Source: 2nd Australian Corps Intelligence War Diaries, July–September 1945
To preserve the use of stored ammunition, Japanese gunsmiths removed the faulty propellant charge from the grenade and drilled a hole in the base, allowing the rifle barrel to enter the body. After firing a blank cartridge, propellant gases inflated the grenade's driving band, which engaged the rifling of the grenade launcher barrel and ensured a seal.
The weapon was typically fired at an elevation of approximately 45°, but could also fire flat fire at close range. Its firing range was approximately 30 to 300 yards (27–274 m).
A drawing of the Type 89 grenade launcher barrel and a projectile for an improvised rifle-grenade launcher. Note that the rifle barrel protrudes into the propellant chamber of the Type 89 projectile. With this design, when the blank cartridge was fired, expanding propellant gases forced the projectile's leading band into the grenade launcher barrel's rifling, creating an obturation (airtight seal). This obturation allowed the projectile to travel a considerable distance. Source: 2nd Australian Corps Intelligence War Diaries, July–September 1945
American intelligence noted that this solution was another invention by Captain Nomura of the 6th Division's research workshops, who was also involved in developing improvised mines and grenades. The Australians captured seven such rifles. All were based on the 6,5mm Type 38 rifle. The existence of a variant based on the 7,7mm Type 99 rifle is also confirmed by the Royal Armouries Museum collection.
Foreign copies and influence
The success of Japanese grenade launchers led to the emergence of imitations and attempts to create similar systems abroad.
In China, the Hanyang Arsenal produced a small batch of Type 10 copies as early as 1934. Later, Factory No. 30 developed the Type 27 grenade launcher, which was very similar in design to the Japanese model. Since 1939, over 40,000 of these grenade launchers and over 1.5 million rounds have been produced.
Chinese training grenade launcher Type 27. Source: 抗战机密档：中日军队轻武器史料
American documents from the end of the war explicitly stated that Japanese troops used captured Type 27s from the Chinese. The Americans characterized the Chinese weapons as cruder in design, but generally similar to the Japanese design.
A close-up of the exhaust port. By rotating the control dial, the valve can be adjusted from fully open to fully closed; at the top, it's partially closed, at the bottom, it's fully open. Source: [Unrelated source:]
The Japanese grenade launcher concept influenced more than just Chinese weaponry. In the 1930s and 1940s, Japan and Thailand maintained close military-technical ties. The Thai army purchased Japanese small arms, artillery, and ammunition, and Japanese specialists participated in the modernization of the country's armed forces. In this context, the family of Thai 51mm rifle grenade launchers for rifles—the Type 46, Type 47, Type 66, and Type 83—is of particular interest.
Thai Type 78 projectile for rifle grenade launchers. Source: 2483 Reenactment Group
According to American postwar reports, these systems weighed approximately 1,4–1,8 kg (3–4 lb), had a barrel length of approximately 254 mm (10 in), and a maximum range of approximately 500 yards (457 m). Their primary ammunition was the Type 78 grenade (1935), a fin-stabilized 51 mm projectile, shaped more like a light mortar shell than a traditional rifle grenade.
Thai rifle grenade launchers. Source: 2483 Reenactment Group
The appearance of Thai grenade launchers is strikingly similar to the Japanese Type 10 and Type 89. Their barrel is virtually the same size as the Japanese grenade launchers, but instead of a separate base plate and trigger mechanism, a standard rifle is used, serving both as a support and as a source of propellant gases. Surviving examples have a distinctive ring with a notch and a locking clip near the breech. It is possible that this ring regulated the propellant gas pressure, similar to the gas regulator on the Japanese Type 10, although reliable confirmation of this hypothesis has not yet been found.
Grenade launchers generated no less interest in the United States. In 1942–1943, the Marine Corps began exploring the possibility of creating a lightweight recoilless mortar designed for jungle warfare and capable of replacing the 60mm mortar.
One of the projects was a recoilless mortar designed by Melvin Johnson (the same inventor of the rifle and machine gun). A single prototype was produced. During testing, a remarkable incident occurred: one of the shells failed to explode and drifted into the forest. Johnson personally went to search for it, located the ammunition, and carried it to a nearby frozen lake to dispose of the dangerous find. Along the way, he slipped on the ice, and later admitted that only then did he realize the full danger of carrying an unexploded shell.
A mortar designed by Melvin Johnson. Source: Johnson Rifles and Machine Guns
The project was not developed further, but the very interest of the American military in such a weapon shows how strongly the Type 89 impressed its adversaries.
A curious example of the longevity of the compact 50mm grenade launcher concept is the Vietnamese-developed STA-50 silent mortar (Súng cối triệt âm STA-50), details of which were published in 2017. The weapon was developed by specialists at the Vietnamese Ministry of Defense's Armament Institute in collaboration with the Z117 plant and uses special CTA-50 ST silent fin-stabilized mortar rounds.
The STA-50 silent mortar and CTA-50 ST silent mortar rounds, manufactured in Vietnam. Source: Vietnam Defense Television
Despite the use of a modern gas-canceling system inside the ammunition, the STA-50 is surprisingly similar in appearance to the Japanese Type 10 and Type 89 grenade launchers: it is also a light weapon of approximately 50 mm caliber, consisting of a short barrel, a stand, and a base plate.
Conclusion
The Type 10 and Type 89 grenade launchers were among the most original achievements of Japanese weapons design during the interwar period. The Type 10 laid the foundations for the concept of a lightweight close-support grenade launcher, while the Type 89 perfected it, combining light weight, long range, and a high rate of fire. Numerous Allied reviews indicate that the Type 89 was considered one of the most effective infantry support weapons used by the Japanese army during World War II.
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