Type 91 Grenade
Encyclopedia
The was an improved version of the Type 10
fragmentation
hand grenade
/rifle grenade
of the Imperial Japanese Army
. Although superseded as a hand-thrown weapon by the Type 97
by the start of World War II
it was still used by units in the Second Sino-Japanese War
and by reserve forces, as well as the Japanese Navy's
Special Naval Landing Forces.
mechanism made the Type 10 almost as much of a menace to the thrower as to the recipient. Furthermore, the weapon was regarded as undersized, and lacked desired lethality. In 1931, the Army Technical Bureau developed an improved version intended to address these issues. After carefully studying employment of grenades and mortars
on the battlefield, the Japanese Army developed a unified system of hand grenade
s, rifle grenade
s, and grenade/light mortar shell dischargers ideally suited to warfare in typical short-range combat environments such as urban, trench, and jungle warfare.
As part of this concept, the Japanese Army had adopted by 1932 a set of fragmentation grenades with almost universal adaptibility. The Type 91 fragmentation grenade could be thrown by hand, fired from a rifle via a spigot-type launcher, or used in a mortar-like grenade discharger, the Type 89
.
, or a finned tail assembly for use as a rifle grenade
, fired from a spigot-type launcher. The fuse was a percussion
-activated delay type, initiated by pulling out a safety pin and striking the top of the cap. The grenade incorporated a 7-8 second delay before detonation. This feature was incorporated as part of the Type 91's other uses as a rifle grenade
or as a shell fired from the Type 89 grenade discharger
, as the long delay enabled longer time-in-flight to distant targets. When used as a rifle grenade with a tail assembly added or mortar round with a base containing a primer and propelling charge, the fuse activated automatically, as the plunger was pushed in against a weak creep spring by the force of the launch. Additionally, the Type 91 could be used as a booby trap
by removing the safety pin and setting under a floor board or chair.
However, the Type 91, as well as other Japanese hand grenades suffered from faults in manufacturing and production of the fuse, grenade body, and explosive compound, resulting in inconsistent detonation, variable fuse burning times, and incomplete or variable fragmentation of the grenade body. During the war, these manufacturing issues remained unresolved.
or Type 89 grenade discharger, and painting the bottom white. The resulting modified Type 91 was visually almost identical to the Type 97 except for its white base.
men in the Second Sino-Japanese War
and throughout the various campaigns of World War II.
Type 10 Grenade
The was the first fragmentation hand grenade designed and deployed by the Imperial Japanese Army.-History and development:After the Russo-Japanese War of 1904–1905, the Japanese army experimented with a variety of grenades; however, no design reached mass production...
fragmentation
Fragmentation (weaponry)
Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...
hand grenade
Hand grenade
A hand grenade is any small bomb that can be thrown by hand. Hand grenades are classified into three categories, explosive grenades, chemical and gas grenades. Explosive grenades are the most commonly used in modern warfare, and are designed to detonate after impact or after a set amount of time...
/rifle grenade
Rifle grenade
A rifle grenade is a grenade that uses a rifle-based launcher to permit a longer effective range than would be possible if the grenade was thrown by hand...
of the Imperial Japanese Army
Imperial Japanese Army
-Foundation:During the Meiji Restoration, the military forces loyal to the Emperor were samurai drawn primarily from the loyalist feudal domains of Satsuma and Chōshū...
. Although superseded as a hand-thrown weapon by the Type 97
Type 97 grenade
The was the standard fragmentation hand grenade of the Imperial Japanese Army and Imperial Japanese Navy SNLF during the Second Sino-Japanese War and World War II. -History and development:...
by the start of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
it was still used by units in the Second Sino-Japanese War
Second Sino-Japanese War
The Second Sino-Japanese War was a military conflict fought primarily between the Republic of China and the Empire of Japan. From 1937 to 1941, China fought Japan with some economic help from Germany , the Soviet Union and the United States...
and by reserve forces, as well as the Japanese Navy's
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...
Special Naval Landing Forces.
Background and development
The Japanese Army, noting that grenades were short-ranged weapons, began efforts to optimize these weapons for close-in infantry fighting. The first hand-thrown fragmentation grenade was the Type 10. Soon after introduction of the Type 10 grenade to front line combat troops, a number of issues arose. When hand-thrown, instability and inaccuracy of the fuseFuse
The word fuse has several meanings:* Fuse , a device used in electrical systems to protect against excessive current....
mechanism made the Type 10 almost as much of a menace to the thrower as to the recipient. Furthermore, the weapon was regarded as undersized, and lacked desired lethality. In 1931, the Army Technical Bureau developed an improved version intended to address these issues. After carefully studying employment of grenades and mortars
Mortar (weapon)
A mortar is an indirect fire weapon that fires explosive projectiles known as bombs at low velocities, short ranges, and high-arcing ballistic trajectories. It is typically muzzle-loading and has a barrel length less than 15 times its caliber....
on the battlefield, the Japanese Army developed a unified system of hand grenade
Hand grenade
A hand grenade is any small bomb that can be thrown by hand. Hand grenades are classified into three categories, explosive grenades, chemical and gas grenades. Explosive grenades are the most commonly used in modern warfare, and are designed to detonate after impact or after a set amount of time...
s, rifle grenade
Rifle grenade
A rifle grenade is a grenade that uses a rifle-based launcher to permit a longer effective range than would be possible if the grenade was thrown by hand...
s, and grenade/light mortar shell dischargers ideally suited to warfare in typical short-range combat environments such as urban, trench, and jungle warfare.
As part of this concept, the Japanese Army had adopted by 1932 a set of fragmentation grenades with almost universal adaptibility. The Type 91 fragmentation grenade could be thrown by hand, fired from a rifle via a spigot-type launcher, or used in a mortar-like grenade discharger, the Type 89
Type 89 Grenade Discharger
The , inaccurately known as a knee mortar by Allied forces, is a Japanese grenade launcher or light mortar that was widely used in the Pacific during the Second World War.-Background:...
.
Design
The design of the Type 91 grenade was almost identical to the earlier Type 10. The main difference was the Type 91’s dome top as opposed to the Type 10's serrated top. As with the Type 10, a threaded socket in the bottom of the body allowed for the attachment of an auxiliary propellant canister for use in a grenade launcherGrenade launcher
A grenade launcher or grenade discharger is a weapon that launches a grenade with more accuracy, higher velocity, and to greater distances than a soldier could throw it by hand....
, or a finned tail assembly for use as a rifle grenade
Rifle grenade
A rifle grenade is a grenade that uses a rifle-based launcher to permit a longer effective range than would be possible if the grenade was thrown by hand...
, fired from a spigot-type launcher. The fuse was a percussion
Percussion cap
The percussion cap, introduced around 1830, was the crucial invention that enabled muzzleloading firearms to fire reliably in any weather.Before this development, firearms used flintlock ignition systems which produced flint-on-steel sparks to ignite a pan of priming powder and thereby fire the...
-activated delay type, initiated by pulling out a safety pin and striking the top of the cap. The grenade incorporated a 7-8 second delay before detonation. This feature was incorporated as part of the Type 91's other uses as a rifle grenade
Rifle grenade
A rifle grenade is a grenade that uses a rifle-based launcher to permit a longer effective range than would be possible if the grenade was thrown by hand...
or as a shell fired from the Type 89 grenade discharger
Type 89 Grenade Discharger
The , inaccurately known as a knee mortar by Allied forces, is a Japanese grenade launcher or light mortar that was widely used in the Pacific during the Second World War.-Background:...
, as the long delay enabled longer time-in-flight to distant targets. When used as a rifle grenade with a tail assembly added or mortar round with a base containing a primer and propelling charge, the fuse activated automatically, as the plunger was pushed in against a weak creep spring by the force of the launch. Additionally, the Type 91 could be used as a booby trap
Booby trap
A booby trap is a device designed to harm or surprise a person, unknowingly triggered by the presence or actions of the victim. As the word trap implies, they often have some form of bait designed to lure the victim towards it. However, in other cases the device is placed on busy roads or is...
by removing the safety pin and setting under a floor board or chair.
However, the Type 91, as well as other Japanese hand grenades suffered from faults in manufacturing and production of the fuse, grenade body, and explosive compound, resulting in inconsistent detonation, variable fuse burning times, and incomplete or variable fragmentation of the grenade body. During the war, these manufacturing issues remained unresolved.
Variants
As a hand-thrown grenade, the 7-8 second delay of the Type 91 proved too long in actual combat, enabling the enemy to pick up and throw the grenade back. To resolve this, the Type 97 fragmentation grenade was adopted for hand-thrown use. In addition to a four-second delay, the Type 97 had no provisions for attaching a tail assembly for rifle grenade use, or a propellant base for firing by grenade projector. These changes prevented accidental usage in the latter roles while simplifying production. When the Type 97 with its shortened delay came into production and was being delivered to front line combat units, the Japanese Army continued to use the older Type 91 grenades as hand-thrown weapons, in addition to rifle and grenade projector use. Many of the Type 91 grenades were modified by shortening the fuse to a four to five second delay, drilling out the base, and welding small extensions on the body, so that it could not fit into the Type 10Type 10 Grenade Discharger
was a Japanese smoothbore, muzzle loaded weapon used during the Second World War. It first entered service in 1921. The Type 10 has a range of 175 meters, greater than other grenade dischargers of that time. It had a range control device at the base of the barrel in the form of a graduated thimble...
or Type 89 grenade discharger, and painting the bottom white. The resulting modified Type 91 was visually almost identical to the Type 97 except for its white base.
Combat record
The Type 91 (modified) was issued as a standard hand grenade to Japanese infantryInfantry
Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...
men in the Second Sino-Japanese War
Second Sino-Japanese War
The Second Sino-Japanese War was a military conflict fought primarily between the Republic of China and the Empire of Japan. From 1937 to 1941, China fought Japan with some economic help from Germany , the Soviet Union and the United States...
and throughout the various campaigns of World War II.