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Type 99 AT Grenade

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The Type 99 was an AT Grenade, also commonly called a mine that was used by Japan during World War II.


It is actually incorrect nomenclature to call the Type 99 a mine because the Type 99 is meant to be thrown and even has a grenade like fuse however this is a common mistake made by historians. It had a ten-second delay before detonation and was magnetic. The four magnets are located at each of the four "corners". To activate the grenade, one must pull the safety pin and give the cap covering the fuze a strong hit.[1] Contained inside the grenade is approximately 680 grams worth of TNT explosive, though the penetrative power of the weapon was limited to 20mm worth of armor penetration, 30mm should the grenades be stacked.[2]

The total weight of the grenade itself was about 1.25 kilograms, with a diameter of 12 centimeters. Considering the low armor penetration, the grenade was most effective when placed on the top side of armor, as without a shaped charge, the weapon relied on the shear blast force to do any damage to tank and crew.[3]


Coming into World War II, Japan had no intentions of armor on armor warfare or even extensive armor use to the point where it became a severe problem. In the minds of many of its tacticians, the tank was a weapon to be used most effectively alongside infantry.

Type 99 Grenade, dud

An American tanker looks at the unexploded Type 99 AT grenade placed on the side of his tank, 1943

This can be demonstrated through the design of many Japanese tanks, light, fast, and efficient cross-country performance. However, it was quickly realized upon looking on many Western tactics that some sorts of anti-tank weapons would need to be given to Japan's infantry. Therefore, in 1939, the Type 99 AT grenade was issued standard to many Japanese infantry units.

Prototype testing for the weapon though was extensive, with testing going on as early as 1935. The results for the Type 99 were excellent, though the tests were based around Japanese tanks, thus not showing the weapon's true combat effectiveness against heavier Allied tanks that would be used later in the Pacific War. In total, thousands of Type 99s had been produced during the war and given to various Japanese infantry units. 


  3. Rottman, L. Gordan. World War Infantry Anti-Tank Tactics. Osprey Publishing (2005), Page 58

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