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"Three Japanese Incendiaries" from Tactical and Technical Trends

The following U.S. intelligence report on Japanese incendiary grenades and incendiary mortar shells was published in Tactical and Technical Trends, No. 22, April 8, 1943.

[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.]


Aside from incendiary bombs, the Japanese are reported to have at least two types of incendiary grenades and at least one type of incendiary mortar shell. For general information on Axis incendiary munitions, see Tactical and Technical Trends, No. 14, p. 12.

a. Half-kilogram Incendiary Grenade

This grenade, 50-mm in diameter, approximately 5.3 inches in length, and weighing 1.1 pounds, may be thrown by hand or projected with a heavy grenade discharger, sometimes mistakenly called a "knee mortar," The incendiary filling (white phosphorus) is contained in a brass body. An attachment consisting of a propellant and a percussion cap is screwed into the base of the grenade for projection with the grenade discharger. When thrown by hand, this attachment is removed. Before use, the safety pin is withdrawn. The safety pin serves the double purpose of holding a light brass cover in place and of preventing downward movement of the firing pin onto the percussion cap. The firing pin is then held off the percussion cap by a creep spring, upward movement being prevented by the light brass cover which is crimped in the middle and engages in a "V" groove cut around the ignition tube.

[Half-kilogram Incendiary Grenade]

When used by hand, the head of the ignition tube is given a sharp tap to drive the firing pin onto the percussion cap. After a delay of 4 to 5 seconds, a fuse detonates the burster, scattering the phosphorus. When used with the grenade discharger, the shock of discharge has the same effect as tapping the grenade when thrown by hand.

b. Incendiary Hand Grenade

This weapon has a diameter of 2.2 inches and an over-all length of 13.5 inches, including the wooden handle 5.3 inches in length.

The incendiary filling of the grenade is composed of white phosphorus and carbon disulfide with 41 cylindrical rubber pellets. Upon explosion, these pellets are scattered and bounce about, igniting any inflammable matter with which they may come in contact.

[Incendiary Hand Grenade]

The detonating apparatus for this grenade is similar to that of the 1/2-kilogram incendiary grenade previously described, except that the fuse gives a delay of 6 seconds.

c. 90-mm Incendiary Mortar Shell, Type '94'

The incendiary filling in this bomb is similar to the hand grenade described in paragraph b above, being composed of white phosphorus and carbon disulfide with 40 cylindrical rubber pellets.

[90-mm Incendiary Mortar Shell, Type 94]

The tail arrangement is designed for one primary and six secondary charges.

The total weight of the bomb is given as 11.6 pounds, the incendiary filling as 2.2 pounds, and the burster charge as 2.8 ounces, while the over-all length is 16 inches. Its maximum range is reported to be about 4,000 yards.

* Based on a Chemical Warfare Intelligence Bulletin, Office of the Chief, Chemical Warfare Service.


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