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Re: PTO Here we go!

Posted: Wed Feb 18, 2015 11:39 pm
by Truscott Trotter
The grenade discharger was the Type 89, the legendarily mistranslated 'knee mortar'. The launcher was nothing more than a means of propelling a hand grenade type round some 600 plus metres. - Bayonetstrength
Japanese use of the Model 89 grenade discharger as a low-angle direct-fire weapon has been definitely indicated, according to recent reports. To use the weapon in this manner, the piece must be emplaced at an angle about 15° from the horizontal. With the Model 89 shell, direct laying at ranges of 50 to 100 vards has been reported as effective. However, this shell has a contact fuze, and premature explosions will occur if trees or other obstructions are in the line of fire.

The fragmentation hand grenade Model 91, adapted for use in the discharger, can also be used for direct fire at ranges up to 60 yards. Principal advantage of the hand grenade is its time fuze (6 to 7 seconds) which will not detonate if it passes through light obstructions, thus allowing its use from behind foliage.- Lone Sentry

Grenade Dischargers
Grenade dischargers are designed for use as an individual infantry weapon to bridge the range gap between hand grenades and mortars. For some time these grenade dischargers were erroneously called "knee mortars" but, as a matter of fact, the base plate is made to rest on the ground not on a soldier's knee or thigh-while the discharger is being fired. The Model 89 (1929) 50-mm discharger is utilized in Japanese infantry tactics to help pin opposing forces to the There is no safety device on the weapon. It is set for the ground during an attack. Ordinarily three or four such dis-chargers are issued to the 4th squad of Japanese infantry platoons.

EDIT my conclusion form admittedly limited research - treat it as a normal grenade launcher - not light mortar

Re: PTO Here we go!

Posted: Thu Feb 19, 2015 3:01 am
by Teufelhunden
The Type 89 HE round (not the Model 91 grenade) was nearly the same size as the British 2", and German and Russian 50mm, and had a longer range than the 2" and German. Whatever changes we make to the Type 89 I believe would need to apply to the 2" other 50mm mortars.

One possible solution to reduce the Type 89 effectiveness is to treat them like rifle grenade dischargers if they are in the jungle/forest with overhead trees (reflecting the more probable use of the model 91 grenade). If they are firing from areas with open overhead they are treated as light mortars.

Another possible solution would be that they can only fire at what is in their LOS, or they have a LOS to a SL or JL that has LOS to the target, or are within a SL/JL command radius.

Re: PTO Here we go!

Posted: Thu Feb 19, 2015 8:14 am
by sackatatties
Just to divert the current topic for a sec. I've noticed that there is only 9 men per section in the 1942-45 Japanese list Type-A units (1942-45). For a Type-A unit this should be 15 total per section inc 1 LMG and 1 NCO or 4 Type 89s.

Back on knee mortars. Remember that these effectively filled both Light mortar AND grenade discharger roles depending on the ammunition used. I think that's where the difficulty lies.
They were certainly more effective than the standard rifle grenade. They also had a longer more accurate effective range than the equivalent 2"/50mm mortars used by other countries mainly because they were rifled. In comparison the British 2" was notoriously inaccurate (but was intended to provide smoke so that wasn't a big issue).
The type 89s WERE effective and I think their use is fairly well represented within the rules. However some see them as causing an imbalance and see a need to neuter them. This may well be in the interests of the game but we need to be careful.

In any case whatever solution decided on needs to be kept simple to stay within the spirit of the rules.

A simple solution:
Leave them as they are but limit ALL integral light mortars to 3 rounds. Perhaps allowing the use of a JoP for a chance to replenish. This way the effectiveness can be reduced without complicating the rules further.

Re: PTO Here we go!

Posted: Thu Feb 19, 2015 12:27 pm
by Richard
Sack (for want of a better name)

I took the strength figures from my US War department manual on Japanese forces, and looking back today I simply cannot find where I got 9 men from! It should indeed be 14 plus an NCO. I also cannot see where I got four grenade dischargers from either. I will have to read this all again.


I've been looking at mortars and the weapon was not just a grenade launcher, it could fire 2" shells as well, the grenade was the round of choice when there was a heavy canopy where the 7 second fuse meant it didn't detonate if it caught a branch or similar. They were fired in very much the same way as the British mortar - aiming is a matter of experience as opposed to science. They would be inaccurate in the hands of an inexperience man, but like the British 2" mortar they were very simple to use and a good man could use them to great effect. Also, they appear to have carried large amounts of ammunition, especially in an island defence situation.

So, that develish dog Teufelhunden seems to be on the money for me. Treat them as mortars if they are in the open, as grenade launchers if in canopy. So, all firing hits on 5 and 6 as everything is at effective range. Let's assume three to a section, then we get six dice, average of two hits. Reduces cover by one.

Any thoughts on that? It doesn't seem too drastic to me.


Re: PTO Here we go!

Posted: Thu Feb 19, 2015 3:35 pm
by sackatatties
Seems reasonable to me Rich.

The 4xDischargers per section in a type A is actually correct according to the USMC manuals on Japanese organisation (3xDischargers in Type B).

See here: ... B-3.html#I (also posted earlier in this thread)

If you scroll down you'll see (for a type-A):

3 Rifle platoons (each 62). 186 officers and men.

1. No. 1 Rifle platoon.
Platoon commander x1
Liaison noncommissioned officer x1
3 rifle-light machine gun sections (noncommissioned officer and 14 men)
1 grenade discharge section (noncommissioned officer and 14 men)

2. No. 2 and No. 3 rifle platoons. Same as No. 1.

Equipment. There are in the company 150 rifles, 9 light machine guns, and 12 grenade dischargers.

Re: PTO Here we go!

Posted: Fri Feb 20, 2015 12:13 am
by Neil Todd
Hi Richard, this is my first post here. I am a keen user of the Japanese force in CoC and previous games I have played. I think the rules you have proposed capture the 'Knee Mortar' well and in fact improve slightly from the way I have been playing it.
From my reading it was one of the weapons that the Japanese used that was truly feared, you did however touch on a point above that may have to be explored further. As the war progressed the quality of training of the Japanese soldier degraded significantly as such they would not have been as accurate with their mortars.
Finally in the games of CoC I have been playing I have rolled my six dice as three different pairs of two so I can have my Mortars run out of ammo on a double 1 even though I had been using them as rifle grenades that don't? run out of ammo

Cheers Neil

Re: PTO Here we go!

Posted: Fri Feb 20, 2015 5:26 am
by Teufelhunden
Just a quick note on the organization types. The "B" type was the standard organization, and most frequently encountered, whereas the "A" type was the strengthened. I see the list states it is based on the "A" type of organization, but then it also states that it is based on the Standard organization, which would be the "B" type of organization. This would be 13 man squads (both LMG and GD), with 3 "knee" mortars in the GD squad. Same source as Sackatatties provided as well as Rottman in the Osprey Battle Orders series.

Re: PTO Here we go!

Posted: Fri Feb 20, 2015 10:32 am
by Richard
The link Mr Sack provided shows lots of snippets from the US War Department Technical Manual, Handbook on Japanese Military Forces from September 1944. I have the original of that here. Most sources seem to use this as a baseline, certainly things like Colonel Forty's handbook and the Ospreys do.

So, as I see it, our platoons look like this:

B TYpe Organisation
Platoon HQ: Lieutenant (senior) sword + pistol, plus NCO (senior) rifle

Thee LMG squads of: NCO (Junior) rifle, one LMG with three crew, nine riflemen
One Grenade Discharger squad of: NCO (Junior) with three dischargers, each with four crew


A Type Organisation
Platoon HQ: Lieutenant (senior) sword + pistol, plus NCO (senior) rifle

Thee LMG squads of: NCO (Junior) rifle, one LMG with three crew, eleven riflemen
One Grenade Discharger squad of: NCO (Junior) with three dischargers, each with four crew

Okay, that seems clear to me IF we accept this US document as gospel. I would prefer to see Japanese sources, which is what I have done with every other nation, but whilst I can struggle by in Romanian and Dutch, there is no chance of me dabbling in Japanese!

My next questions are as follows:

When do we use A and when B lists?
Should there be a difference in the core platoon organisation between 1941 and 1945?
Do we want to reflect weakened units later in the war (disease etc.)?

I feel that we are getting there with this now. I have to admit to having a mental block with Japs. My Uncle was a POW at their hands and as a result I have never gamed them, despite them being an interesting force.


Re: PTO Here we go!

Posted: Fri Feb 20, 2015 11:08 am
by Emilio
Rich, I´ve got a few pics from a japanese book that may be useful for you (and everybody, ofcourse). Take a look here: ... _M6ya?dl=0

The LMG has a crew of four.

Sadly, no knee mortars.

Re: PTO Here we go!

Posted: Fri Feb 20, 2015 11:14 am
by rim66
Hi Rich,

You have 3 GD in the Type A, I think someone mentioned it should be 4.

I know only Type B was used in Burma. I think, but would have to check, that Type A was more Manchuria/China but I would need to check.

I don't think there should be a difference in core platoon 41-45, although, as said, quality may well drop.

Weakened platoons - the base should be book to be consistent, but I would provide notes allowing the dropping of the rifle element of a section in return for extra support. This could allow 3 LMG teams in bunkers and the odd marksman, certainly typical of late war Burma.

I do also wonder if the Plt Sgt should be less than a senior leader. I certainly don't think he is like a British Plt Sgt. Just one for debate.

Richard/Monty Lardo