Grenades are particularly useful to the close-in tactics of jungle fighting and the Japanese have
used them extensively in their operations in the southwest Pacific and Burma areas, especially with
grenade throwers. The following information on Japanese grenades is therefore of interest.
(a) Hand grenade. A grenade examined in Burma is described as follows (see accompanying
sketch): The grenade is cylindrical in shape and has a grooved cast-iron body. A plug (10) is
screwed into the top of the body through which extends a brass igniter tube (4). The
striker (5) with holder (3) creep spring (6) and percussion cap (7) are
located in the upper part of the tube while the lower portion contains the fuse and
detonator (14). The tube is closed at the top by a light brass cover (1) crimped near
the middle to fit into a groove in the tube and held in position by a safety pin (2). The
safety pin supports the striker holder and prevents the downward movement of the striker on to
the percussion cap. The fuse and detonator are separated by a perforated steel disk (15). The
filling (16) is composed of T.N.T.
The dimensions and weights are:
|Maximum diameter|| ||1.97 in.|
|Overall length|| ||3.78 in.|
|Weight|| ||16.5 oz.|
|Weight of filling|| ||2 oz.|
|Japanese Hand Grenade|
Method of arming. Withdraw the safety pin. The spring is then held at half compression
by the brass cover. Give the head of the ignition tube a sharp blow, further compressing the
spring and driving the striker on to the percussion cap. The fuse, with a delay
of 4-5 seconds, is then ignited and the filling detonated.
To disarm grenade. Remove safety pin and cover. Withdraw striker holder and
spring. Unscrew plug at top of grenade and withdraw together with ignition tube. Withdraw
copper tube from bottom of plug and remove detonator. Remove filling.
Variant type. A grenade examined in England sometime ago was slightly heavier, but
otherwise was very similar in appearance and dimensions. A cartridge
container, diameter 1.02 in., length 1.22 in., screwed into the base of the
body, contained a propelling charge and percussion cap. This is presumably fitted when
the grenade is fired from a discharger, probably the 1.97-in. grenade
thrower, model 89.
(b) Stick grenade. A grenade of this type was examined in the Far East. (See
accompanying sketch.) It is similar in design to the German stick grenade 24, the
main points of difference being as follows:
||German grenade 24||
|Length of stick||
|Length of container||
|Diameter of container||
||1 ft. 2 in.||
||1 lb. 2 oz.||
||1 lb. 3.5 oz. (approx.)
|Weight of filling||
||6 oz. (T.N.T.)||
||2 oz. (Lyddite)
|Thickness of casing||
|Japanese Stick Grenade|
Both grenades are operated by a friction-igniter, powder-delay system and
have a delay of approximately 4 1/2 seconds.
The thick cast-iron casing and smaller charge of the Japanese grenade indicate
that it is designed for fragmentation, in contrast to the German grenade
which relies on blast for its effect.
Method of arming. Remove screwed metal cap from base of stick and take out
wire ring. Insert middle finger in ring and retain when throwing grenade. When
grenade is thrown, cord attached to ring will be pulled out, igniting fuse which
burns for about 4 seconds.
To disarm grenade. Remove the wax around the joint between stick and container
and take out three screws located about 1/2 in. from the base of the container. Hold
the grenade by the handle and tap off the container. Remove filling. Remove screwed
metal cap from base of stick and cut cord away from ring. With a metal rod, push out
igniter, fuse, and detonator complete.
(c) Armor piercing magnetized grenades. These grenades are designed to detonate
while clinging to the armor as a result of their magnetic qualities. It has been
reported that the Japanese have 2 types, one shaped like a flat-sided disk, the other like a
bun with a flat base. The former must be actually placed against the armor by the
soldier; the magnetic qualities of the other grenade are such that it can be thrown
from a distance of 10 yards, but since the flat surface must come in contact
with the armor this form of attack is not likely to be successful. It is thought
that these grenades are not likely to be very effective since, among other things, even a
small air space between the armor and the grenade would defeat its penetrating power.
While information has been received confirming the existence of these grenades, there is no
evidence that they have been used in battle.