"Use of the Type 89 "knee mortar"" Topic

Hey all---has anyone come across a field manual, Allied assessment, after action report, or Japanese document that explains the use of the light Type 89 grenade launcher/mortar? I'm interested in their battlefield use. Did the Japanese mass them, attachment them out to support individual infantry squads, employ them for direct fire or hold them back like conventional mortars, or what?

Interested in peoples' thoughts and knowledge on the subject.

Off hand, I believe there was one per squad in one of the infantry division TO&Es. It's been a long time and I don't have the references to hand, though, so I could be wrong. Certainly there was at least one per platoon, if not more. They weren't really mortars – they were actually grenade throwers, thus could be deployed with less training than mortars would have required. I don't recall reading anything about them being massed – rather, they were used in the sense of a squad or platoon support weapon, and they were direct fire weapons, though were probably capable of simple indirect fire (firing over a ridge or berm with directions from someone sitting on top of the ridge or berm).

They are direct fire weapons, with a max range of only a couple hundred yards and that's with long range rounds. Not massed, but each platoon would have 2-3 of them in a support squad that got parcelled out through the platoon. One guy with the mortar, a couple to hump the ammo with each round weighing about a pound. Mostly HE with an ineffective smoke round.

Each Japanese infantry platoon had three rifle squads and a grenade discharger squad with three knee mortars. Here's a link to the TO&E for Type B (standard) and Type A (strengthened) rifle companies:

link

And here are a couple of primary source documents discussing the knee mortar:

link

link

Hope that helps,

Mike

Three Type 89 50mm grenade launchers per platoon (four in strengthened and modified strengthened regiments). The ammo was carried in a pair of belt pouches each of which held three grenades.

Thanks for the comments. Delta, excellent links---was aware of the bayonet strength link but not those documents.

Keeping in mind that in early to mid war the main Japanese tactic was assault, these were primarily used against enemy positions just prior to the bayonet charge. More effective in mainland Asia than the Pacific islands where overhead foliage would cause premature detonation.

The teams were initially deployed in a fourth squad with some riflemen for protection. As the war progressed Japanese losses, lack of replacements, and equipment shortages resulted in the grenadiers being converted to standard riflemen.

Brigade Games does a nice set of teams. Check out
link
about half way down the page.

Thanks, BAMeyer.

It's also worth noting that the standard infantry hand grenade could be used as the projectile in the knee mortar.

This means rather small charges, but a lot of rounds available to use.

Interesting – I see they are referred to on the Brigade Games page as "Ni Mortars". Is that an indication that the name is a misunderstanding of a Japanese word sounding like "knee" but having nothing to do with the leg joint? I am well aware that the name "knee mortar" doesn't indicate that it was fired from off your knee or anything stupid like that, but I have never heard the reason why it had that name at all.

There are at least 100 different stories claiming to explain the knee and Ni nomenclature. One of the more plausible is a mistranslation resulting in the word knee and then a Japanazation by soldiers back to Ni.

Range was set not by tube angle but by regulating the gas escape valve at the base.

They were considered very handy around armour too – hit a tank with a barrage of 50mm rounds to button it up and strip away any escorting infantry, so the tank hunter teams can get close enough to do some damage.

Here is a link to an online copy of SHOTS FIRED IN ANGER a book about combat and weapons in the pacific and Burma theaters. Check page 339 for the chapter on Japanese Grenades which also talks about the knee mortar.

link

Very interesting thread. Thanks guys.

Great info all around!

Dom: That's an interesting tactical note. Thanks for that.

There's rather a good account of it by a sergeant who went hunting Lee/Grants with some success in the excellent "Tales By Japanese Soldiers".

Dom _ I have that great book too and just re-read that account…as someone else says above they used the grenades to separate the Allied inf from the tanks then assaulted the tanks with mines, charges etc thrown into the tracks – approaching the Lees when their gun turret was facing the other way…then using MG on the tank to encourage it to move, thus triggering the mines to explode and throw a track
Andy

"Ni" mortars were used by knights who demanded shrubberies to appease them………

I'll see myself out