Fun with knee mortars!

Ah, knee mortars.

They weren't mortars and they had nothing to do with knees. They were the Imperial Japanese Army's standard grenade launcher. And they were one of the great unsung weapons systems of World War Two.

Light, cheap, simple, easy to carry and maintain, and utterly ubiquitous. One of the few weapons systems where the Japanese managed to outproduce everyone else. The Brits and Americans averaged two or three grenade launchers per infantry company. (The Marines were an interesting exception. The USMC was very sensible about mortars.) The Japanese had one per /squad/. And while their throw weight was light, these little monsters could drop a grenade on your head from 600+ yards away with terrifying accuracy.

They were simple, but they weren't primitive. Their clunky, ugly appearance belied a great deal of careful thought and development. The engagement mechanism for the rifling was elegant, but also easy to disassemble and clean, and made of a copper alloy that had exactly the right mix of flexibility and strength. The whole thing could be broken down into four lightweight pieces, just a few pounds each, which could be carried without difficulty by various squad members then reassembled in a few moments.

Sighted with two lug nuts -- a monkey could do it. But in practiced hands (and because they were ubiquitous and cheap, there were a lot of practiced hands), amazingly accurate. Fully functional under conditions from rain forest downpour to Aleutian blizzards. Easy to use, almost impossible to break.

Read any US memoir of the Pacific War, and you'll realize just how much American soldiers came to hate and fear these things. Knee mortars probably killed far more Americans than Zeroes or Long Lances ever did, and at a tiny fraction of the cost.

All the other combatants had grenade launchers too, of course. But they tended to be bigger -- the standard US 60mm launcher weighed 43 pounds as opposed to 12 for the knee mortar -- and much less common.

(True, the US grenade launcher had a throw weight about 50% greater and nearly three times the range. But not many WWII infantry actions took place at a range of 2000 yards. To simplify a complex reality, the US weapon was overpowered.)

So, a question: WI we give the knee mortar to some other power's infantry? -- When I say "give the knee mortar", I mean not just the weapon but the whole package: they're light, cheap and reliable, every squad has one, and they're a strongly preferred method of making the enemy miserable.

This seems like something the Russians or Americans would have figured out, doesn't it? Oddly, not.

The Germans... um. Tempting as it is to give the Wehrmacht something this nasty, "light, cheap, reliable and mass-produced" don't seem a perfect fit.

Thoughts?


Doug M.
 

MrP

Banned
Hm, interesting. Not heard of these before - blame my WWI fetish! ;) It'd be interesting to see them in Russian hands in Stalingrad, making the Germans' lives even more difficult. And the simplicity fits the Russian ethos - as far as I understand it, that is.

I'm not sure they'd be apt for the British, since we were more into using rifles than LMGs and SMGs, except, of course élite units. I could see the Paras using them.
 
When the tank companies start rolling into Poland a mass of knee mortars could make a big difference.
Not really... without a proper High Explosive Anti-Tank round they'll do bugger all against anything with more armour than a Panzer I. Simply, plain HE -in the quantities you can fit into something of 40-60mm calibre- lacks the ability to penetrate any real thickness of armour... and any form of high velocity based armour piercing doesn't work with a grenade launcher.
 

Redbeard

Banned
Both the Wehrmacht and the Red Army had similar 50mm mortars, deployed at platoon level, but they found them to anaemic and preferred 81-120mm mortars.

A couple of 81mm mortars at company level suddenly gave the company commander his own organic artillery and a capacity to within very short notice to take any objective inside his operational area under fire (and put up effective smokescreens).

A 120mm platoon/company at battalion level gave the infantry battalion a similar capacity.

The problem with organic mortar firepower usually is that the commander tend to forget to request "real" firesupport from higher echelons (too much trouble, can't wait, they shall not interfere with my business, I can handle myself etc...), but it would be much better to have an army of independently operating companies or battalions than squads. And anyway, if you train your artillery observers and LOs as "Firesupport salesmen" you might approach the ideal co-ordination level.

Regards

Steffen Redbeard
 
Simply, plain HE -in the quantities you can fit into something of 40-60mm calibre- lacks the ability to penetrate any real thickness of armour... and any form of high velocity based armour piercing doesn't work with a grenade launcher.

True. The knee mortar was useless against armor; it was entirely an infantry killer.

But it was a really, really good infantry killer.


Doug M.
 
http://members.shaw.ca/nambuworld/t89pix.htm
This site has some good pictures of the "knee mortar" and shell. Apparently, it's actually called the Type-89 Leg Mortar in some documents because it was carried strapped to the leg (the official name was Type-89 Heavy Grenade Discharger). In captured documents, "Leg Mortar" was mistranslated as "knee mortar"- photos were also found of Japanese soldiers posing with these devices on their knees. Several GIs apparently broke their legs trying to fire them like this!

The site also has some good pictures of the actual firing procedure.
 

Hendryk

Banned
Considering that the Chinese had to fight the Japanese from 1931 to 1945, it's hardly implausible that they could have come across the thing and duplicated it. The Chinese made intensive use of light mortars (mostly, it must be said, for lack of heavier artillery), so this would have been seen as the ultra-light version.
 
Considering that the Chinese had to fight the Japanese from 1931 to 1945, it's hardly implausible that they could have come across the thing and duplicated it. The Chinese made intensive use of light mortars (mostly, it must be said, for lack of heavier artillery), so this would have been seen as the ultra-light version.

Their Chinese. They invented the first out of habbit.:D
 
I think it would be interesting to have a second-tier or minor power be the one to develop this. Maybe Italy? It would suit the war of maneuver in N Africa...

No?
 
Considering that the Chinese had to fight the Japanese from 1931 to 1945, it's hardly implausible that they could have come across the thing and duplicated it. The Chinese made intensive use of light mortars (mostly, it must be said, for lack of heavier artillery), so this would have been seen as the ultra-light version.

The Chinese did copy the Japanese knee mortar. Only their's had no rifling and used a longer tube to compensate. But it was still not as accurate.

This class of 50mm mortars was not unique to the Japanese. Several countries, including the French, British, Germans and Russians had something similar. The Japanese and British designs were the simplest.

It should be noted that after WWII the 50mm rapidly fell out of favor and was replaced by the 60mm mortars. The reason was the 50mm was hard to aim and was only good while you had experienced mortar men. Because the light 50mm mortars were issued at the platoon level, turnover rate was very high and these ended up being used by inexperienced conscripts to poor effect. The 60mm mortars were issued to company, where specialzied mortar teams were able to take advantage of it's superior tripod stabilized mount and optical aiming device.

French Brandt 50mm
50mmMle1937mortar_l.jpg


British 2 inch mortar
2_in.jpg


German 50mm
f1_german_light_50mm_mortar_ww2.jpg


Soviet M1941 50mm
f1_red_army_mortar_m1941_50mm_russian.jpg


On a final note, the 50mm motar isn't completely dead. There is a Belgian design using a captive piston which traps the gas in the tube. This mortar produce little noise and variants are still in service with the French and Chinese in limited applications, ie special forces.
 
The Belgian design is called the Fly-K. Very quiet, yes.

Anyway, uh...the PIAT was a spigot mortar, and though difficult to use a viable antitank weapon. Considering that they were accurate and that the bomb came down from overhead, they might be real terrors to armor if you developed proper HEAT rounds...velocity isn't an issue, and if you can put it on target, the bomb comes down on the much thinner top armor of the tank.

Plus, you know, it might be a good way for partisans to make life hell for supply convoys and stuff...a good way to knock out trucks and armored cars, perhaps.
 
Ah, knee mortars.

Ah, indeed. My favorite infantry light weapon of WWII. One thing you didn't mention: They could fire the Japanese standard hand grenades as well, meaning they could keep going once their ammunition was gone.

As for which other powers could make use of the whole package? Italy. In fact, they would be vastly better than their light mortar, a complex thing firing 47mm grenades(out of clips, IIRC) that was the epitome of too much mortar for too little mortar bomb, even more than the German 50mm mortar.
 
Hmmm...

Italy- North Africa could be interesting with ground support light artillery easy to use and get ahold of. Picture attacking towns, or dug in positions with those things.

Germany- On the east it could be used from Lenin to Stalingrad, and yes tanks are important but fights did occur with infantry all the same. On the west once D-day occurs I can see the knee mortar causing hell for the troops in Beligum in the winter.
 
http://members.shaw.ca/nambuworld/t89pix.htm
This site has some good pictures of the "knee mortar" and shell. Apparently, it's actually called the Type-89 Leg Mortar in some documents because it was carried strapped to the leg (the official name was Type-89 Heavy Grenade Discharger). In captured documents, "Leg Mortar" was mistranslated as "knee mortar"- photos were also found of Japanese soldiers posing with these devices on their knees. Several GIs apparently broke their legs trying to fire them like this!

The site also has some good pictures of the actual firing procedure.
I'd HATE to Hafta Show up at an Aide Station with that Wound ...

They'd Stick you with The Guys who "Accidentally" Shot themselves ...

Who would Promptly Declare you to Be, "The Idiot of The Group!"
 
The Type-89 Heavy Grenade Discharger is a great example of a weapon that was great as deployed by its own Army but doesn't really fit in with
conscript armies as pointed out above due to the training required to properly employ it . It did however have a impact far beyond it's cost in jungle warfare.As pointed out above almost all nations(US not included)
had a similar weapon system during WW2 but was replaced at the PLT level with a 60mm crewed system and a 81mm crewed system at CO level.As this proved to provide a higher rate of accurate fire, as a side note this system has been replaced in US service for Mech/Armor Div's with mortar carriers having either a 120mm or 4.2" mortar.Also today the light mortar role has been inherited by 40mm grenade launchers which are organic at the most basic level(fireteam) in most militaries.
 
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