Chapter IX: Weapons

Section II: Infantry Weapons

4. GRENADES, LAND MINES, AND BOOBY TRAPS. a. General. The following pages give a general picture of Japanese grenades and land mines. Certain of these can be and have been used as booby traps.

b. Booby traps. Although the Japanese use of booby traps has been limited as compared to the German, it is to be expected that these traps will be more and more frequently encountered as Allied Forces push the Japanese from prepared positions. As many types of Japanese ammunition are suitable for employment as booby traps only the most common are listed. The model 23 pull type fragmentation grenade is particularly suitable for this purpose when attached to doors, window frames, and general items of abandoned equipment. In addition numerous reports have been received of captured allied grenades (i.e. British No. 36 and United States MK 2) being similarly employed. Although there is no evidence to date that the stick grenade, the bangalore torpedo, or the explosive cannister from the barrage mortar shell have been used as booby traps, the fact that all have pull igniters and accidents have occurred to troops handling them, prove that they are most suitable as such. The 3 types of fragmentation grenade models 91, 97, and 99 ("Kiska") grenade are equipped with percussion ignited fuses. They have been used with a suspension wire device which can be tripped. The grenade is placed bottom-up inside an improvised tube thus ensuring that the grenade will fall head first so as to detonate the fuse, when a wire is tripped (see fig. 195). A piece of bamboo or empty cartridge case is sometimes used in lieu of a tube.

Figure 195. Illustration of method used by the Japanese to construct a booby trap using model 91 (1931) hand grenade.

Another and less elaborate variation is found in the use of the above listed grenades under a foot board. The delay powder train may be first removed. The weight of the foot fires the detonator instantaneously. Many of the land mines have been used as booby traps and work on the same principle, model 93 being equipped so that it can be activated by pressures from 7 to 200 pounds. Only one or two electrically operated booby traps have been encountered so far. They operate on a low voltage and are generally attached to equipment such as radios and vehicle ignition switches. It can be expected that booby trap fuzes of more advanced design, will probably appear in the near future, as the Japanese are driven back.

c. Model 91 (1931) hand grenade. (1) General description. Model 91 (1931) fragmentation grenade (fig. 196) can be thrown by hand, fired either from models 10 or 89 grenade dischargers, or fired from a rifle grenade launcher (discharger) with tail assembly added. The base contains a primer and propelling charge for use when firing from a grenade discharger.

Figure 196. Model 91 (1931) hand grenade (including propellant charge for use in grenade discharge).

(2) Characteristics.

Over-all length		4.95 inches.
Fuze delay		7 to 8 seconds (approximately).
Diameter		1.97 inches.
Weight with propellant charge		18.8 ounces.

(3) Operation. (a) To arm. With safety pin in position, screw firing pin down into firing pin holder, with screw driver or knife blade, as far as it will go.

(b) To use as hand grenade. Hold grenade with fuze pointing downward, remove safety pin, being sure that safety cover does not fall off. Strike head of fuze against solid object such as helmet keeping hand clear of gas vent hole. Throw immediately since action of fuze is sometimes erratic.

(c) To use in grenade discharger. Remove safety pin and drop into discharger.

d. Model 97 (1937) hand grenade. (1) General description. The model 97 (1937) fragmentation hand grenade (fig. 197) is carried by all front line troops and is almost identical with model 91, except that it has no provision for a base propellant attachment and has a shorter fuze delay time. It cannot be fired from a grenade discharger.

Figure 197. Model 97 (1937) hand grenade.

(2) Characteristics.

Over-all length		3.75 inches.
Diameter		1.97 inches.
Weight		1 pound (approximately).
Fuze delay		4 to 5 seconds (approximately).

(3) Operation. (a) To arm. With safety pin in position, screw firing pin down into firing pin holder as far as it will go.

(b) To throw. Hold grenade with fuze pointing downward. Remove safety pin, being sure that safety cover does not fall off. Strike head of fuse against solid object such as helmet, keeping hand clear of gas vent hole. Throw immediately since time of fuze is sometimes erratic.

e. Model 99 (1939) hand grenade. (1) General description. This grenade has been identified as model 99 (fig. 198). It is smaller than the model 97 and 91 fragmentation grenades and unlike these, it has a smooth, cylindrical body with a flange at either end. It may be launched from a special launcher mentioned previously under "Rifle grenade launchers" (figures 176 and 177).

Figure 198. Model 99 (1939) hand grenade ("Kiska").

(2) Characteristics.

Over-all length		3 1/2 inches.
Diameter		1 5/8 inches.
Weight		10 ounces (approximately).
Fuze delay		4 to 5 seconds (approximately).

(3) Operation. (a) To arm. Remove safety pin which is held in place by a cord.

(b) To use as a hand grenade. Strike the head of the fuze on a hard object and throw immediately. Since the firing pin is integral with firing pin holder no screwing or unscrewing is necessary, as with the model 91 and model 97 fragmentation grenades. It can be used as a booby trap by removing the safety pin and setting under a floor board or chair.

(4) Alternative fuze. It is believed that there is a variation of this grenade, known as the model 99B, which is activated by a friction igniter fuze.

f. Model 23 grenade. (1) General description. This grenade (fig. 199) appears to have been designed for use either as a hand grenade or a booby trap. It has a pull type friction igniter fuze with a time delay reported as approximately 5 seconds. Because a pull (from 2 1/2 pounds to 5 pounds) on the fuze cord ignites the time fuze, it could easily be adapted for use as a booby trap by tying the cord to a trip wire. The lugs and rings on the side are convenient for anchoring the grenade in place when so used. It has also been found in a booby trap with a high explosive artillery shell tied to it for augmenting the power of the explosion.

Figure 199. Model 23 hand grenade.

(2) Characteristics.

Over-all length		3 3/4 inches.
Diameter of body		2 inches.
Weight		1 pound (approximately).
Filler		Granular TNT.

g. 1/2 kg. incendiary grenade. 5.3 inches long and weighing 1.1 pounds (approximately), it may be thrown by hand or projected from the grenade discharger model 89. Incendiary filling is white phosphorus.

h. Incendiary stick grenade. (1) General description. The body of this grenade (fig. 200) is filled with impregnated rubber pellets in a phosphorus carbon disulphide solution. There are some 40 pellets in each grenade, which are scattered by a central bursting charge. It is also possible that this grenade is sometimes filled with phosphorus smoke filling. The grenade is 13.2 inches long and the body has a diameter of 2.1 inches.

Figure 200. Incendiary stick hand grenade.

(2) Operation. (a) To arm. Make sure that the safety pin is in position and that the firing pin is threaded down into the firing pin holder.

(b) To throw. With the fuze pointing downward, withdraw the safety pin. Making sure that the safety cover does not fall off, strike the head of the fuze against some hard object, such as the heel of your shoe or the top of your helmet. There should be no delay in throwing the grenade, since actual fuze delay time is not known.

i. High-explosive stick hand grenade. (1) General description. This is the well known "potato masher" type of grenade with a pressed metal cap at the end of the handle (fig. 201). It has a smooth cylindrical body.

Figure 201. High-explosive stick hand grenade.

(2) Characteristics.

Over-all length		7 7/8 inches.
Diameter of grenade body		2 inches.
Weight of bursting charge (lyddite)		2 3/4 ounces.
Total weight		19 1/2 ounces.
Fuze delay		4 to 5 seconds (approximately).

(3) Operation. Remove the metal cap. A ring with a string attached will be found. This ring is slipped on the finger and the grenade thrown. The string pulls away from the grenade and starts the time fuze burning. This grenade can be used as a booby trap by attaching one end of a trip wire to the ring and the other end to a moveable object such as a door, helmet, etc.

j. Molotov cocktail incendiary grenade. (1) General description. This is a Japanese version of the "Molotov cocktail." It consists of a standard bottle (fig. 202) filled with a mixture of oil and gasoline. (The bottle illustrated in figure 202 is a Japanese beer bottle.) The fuze is an "all-ways" type that will ignite when the grenade is thrown no matter in what position the bottle lands, for the impact drives the firing pin down into the detonator which ignites the contents of the bottle.

Figure 202. Molotov cocktail incendiary grenade with fuze.

(2) Operation. Remove safety pin, then throw.

k. Frangible Smoke Grenade, white. Spherical, flat bottomed glass flask 3 inches in diameter and filled with a yellowish liquid varying from 100 percent titanium tetrachloride to a mixture of approximately 60 percent titanium tetrachloride and 40 percent silicon tetrachloride. The grenade (fig. 203) is packed in sawdust in a cylindrical sheet metal container.

Figure 203. Frangible smoke grenade.

l. Frangible Hydrocyanic Acid (AC) Grenades. Two different types exist. One is stabilized with copper powder and is packed in a sheet metal outer container, the other is stabilized with arsenic trichloride and packed in a cardboard container. The grenade (fig. 204) consists of a spherical glass flask about 3 1/2 inches in diameter containing approximately 1 pint of hydrocyanic acid. The flask is packed in a mixture of sawdust and a neutralizing agent. The outer container is approximately 5 1/4 inches high and 5 1/2 inches in diameter, it is painted khaki and banded in brown.

Figure 204. Frangible hydrocyanic acid grenade, arsenic trichloride stabilized type.

m. Bangalore torpedo. (1) General description. This is the standard bangalore torpedo (fig. 205) for the Japanese Army. It has a pull type delay fuze and is threaded at each end to permit an indefinite number of tubes to be attached end to end. Because of the type of fuze, it may be used in a booby trap, with the igniter string tied to a trip wire.

Figure 205. Bangalore torpedo.

Over-all length (one tube)		46 inches (approximately).
Diameter		2 inches.
Weight (one tube)		10 pounds.
Fuze delay		6 to 7 seconds (approximately).
Charge composition		TNT 36 percent. Cyclonite 64 percent.

(3) Operation. (a) Remove plugs, screw together the selected number of tubes, remove the bullet shaped cap from fuze and place on one end. Screw fuze in place. When ready to detonate the bangalore torpedo, pull out the safety pin, and pull the lanyard (requires about a 13-pound pull). The fuze delay will be approximately 6 to 7 seconds.

Note. Another bangalore type land mine which may be an antitank mine has been found. Its characteristics are as follows:

Length		36 inches.
Width		3.5 inches.
Height		2 inches.
Charge		6 pounds picric acid.
Form		Oval cross section.
Color		Olive drab.
Fuze		4 pressure type shear wire fuzes inside base—pressure about 300 pounds.

(b) For additional information concerning Japanese Bangalore torpedoes see chapter 10, section V, paragraph 5b.

n. Model 93 (1933) mine. General. This mine (fig. 206) is exploded by pressure applied anywhere on its upper surface. It is used either for anti-personnel or antitank purposes. Fuzes are provided with shear wires of various strengths, so the fuzes may function under pressures of from 20 pounds* to as much as 250 pounds depending on the fuze selected. Additional explosive may be placed beneath the mine to give it greater force.

Figure 206. Model 93 (1933) mine.

o. Model 99 (1939) armor piercing mine (grenade). (1) General description. This mine (fig. 207) is issued to infantry units and is carried by the individual soldier. It is sometimes referred to as the "magnetic antitank bomb" or "armor piercing grenade." The magnets serve to hold the mine against a metal surface such as a tank (or iron pill box door) until it explodes.

Figure 207. Model 99 (1939) armor piercing mine, with fuze.

(2) Characteristics.

Diameter		4 3/4 inches.
Thickness		1 1/2 inches.
Total weight		2 pounds, 11 ounces.
Length of fuze		5 1/4 inches.
Charge		1 1/2 pounds TNT.

(3) Operation. Screw fuze into fuze hole. Remove safety pin. Place by hand against object to be destroyed. Give the fuze cap a sharp blow. A time delay of approximately 5 to 6 seconds gives a man time to withdraw. It has been claimed that the mine can be thrown against the target rather than having to be placed there by hand.

p. Model 96 (1936) mine. (1) General description. This is a large, very powerful mine (fig. 208) adapted for use either on land or under water. The two lead alloy horns enclose glass vials containing an electrolytic fluid. Pressure on either of these horns will crush the vial, releasing its contents. This activates the chemical electric fuze thus detonating the mine. Several sizes of this mine are believed to exist.

Figure 208. Model 96 (1936) mine.

(2) Characteristics.

Height of mine		10 1/2 inches (approximately).
Diameter at base		20 inches (approximately).
Total weight		106.5 pounds (approximately).
Charge		46 pounds.

Note. Another type of underwater mine, is an 8 1/2-inch by 8-inch canister, total weight 20 pounds, containing 8 pounds of perchlorate explosive.

*Mines have been reported which function with a pressure as low as 7 pounds.

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