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"Japanese Grenades" from Tactical and Technical Trends

The following U.S. intelligence report on Japanese grenades was originally published in Tactical and Technical Trends, No. 5, August 13, 1942.

[DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]


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]
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     Japanese grenade
Length of stick 10 in. 5 in.
Length of container 4 in. 3 in.
Diameter of container 2.75 in. 2 in.
Length overall 1 ft. 2 in. 8 in.
Weight 1 lb. 2 oz. 1 lb. 3.5 oz. (approx.)
Weight of filling 6 oz. (T.N.T.) 2 oz. (Lyddite)
Thickness of casing .08 in. .25 in.

[Japanese Stick Grenade]
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.


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