IJA heavy mortars

Hi.

There were at least three similar purpose weapons developed after WW1. All these trench mortars were heavy short range guns for firing large explosive charges into enemy positions during attacks or defence operations on short ranges. All were quite large and heavy. These guns had a caliber of 150 mm and larger and were designated "mortar" while all infantry mortars up to 150 mm caliber were designated "grenade launchers" There are series of pictures and drawings of some of these guns in Ground Power Special 2005 "Less Known Army Ordnance of the Rising Sun" Part 1 and 2

Type Taisho 14 27 cm Mortar was a heavy breech-loaded mortar with a horizontal loading position placed on a 360 ° turntable on a heavy circular lower lafette.

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The Type 96 30 cm Mortar was a second, larger weapon of this kind.


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There are additional pictures of the gun parts loaded and in traveling position.


Last was the Type 2 15 cm Mortar. It was more or less a smaller version of the Type Taisho 14 27 cm mortar

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Only few weapons were produced. Successors were the more flexible Type 98 Spigot Mortar and finally the type 4 20cm and Type 4 40 cm Rocket Launchers.

Yours

tom! ;)
 
tom! said:
Last was the Type 2 15 cm Mortar. It was more or less a smaller version of the Type Taisho 14 27 cm mortar
Click to expand...
I didn't know about this one, what was the timeframe it was built and tested in?
 
Hi.

"Type 2" indicates an introduction in Jimmu calendar year 2602 = 1942. So following the standard IJA tech timelines it´s a late 1930th/early 1940s development. Sadly I have not enough knowledge to translate the japanese text fully for further infos.

But the most interesting detail I could identify is a caliber of nominal 150,5 mm to let the weapon fit into the IJA grenade launcher/mortar system.

I wonder why they developed and built such a mortar as there already were 150 mm grenade launchers in the mid 1930th. Additionally the guns were quite complex and far more vulnerable compared to the Type 98 spigot mortar system or the later rocket launchers. To me this was a waste of ressources.

Yours

tom! ;)
 
Could this weaponry be inspired by eg Maginot line and especially those Alpine forts that had 'very big' mortars to provide plunging fire onto potential dead ground ?? IIRC, the French alpine forts held off Italian attack, then German-assisted attack. Yes, there was grim attrition, and damaged positions had to be abandoned, but no faster than expected...

IIRC, one feature was those forts' low-set gun 'ports' / embrasures had deep pits in front, shaped to trap and mitigate 'incoming' ordnance. Tangentially reminded me of the 'Valley of the Kings', where many tombs had a deep pit in front of their entrance. Not to thwart tomb-raiders, but as a precaution against inundation by rare yet devastating flash-floods...

Equivalent of the mud/debris catch-basins up-stream of modern dams and storm gulleys...
 
Hi.

Type 4 30 cm Heavy Mortar Carrier Ha-To.

A 30 cm heavy mortar loaded on an experimental tracked chassis which was later standardised as Type 4 prime mover (see also Type 5 7 cm Gun Carrier Na-To). The suspension was directly taken from the Type 4 Tank Chi-To. Some riveted and welded 12 -25 mm armour plates covered the vital parts.

The gun was developed from the Type 96 30 cm Heavy Mortar. It was muzzle loaded with an ammunition elevation mechanics above the barrel to rise the grenades (enlarged standard mortar grenades).

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The ammunition war raised above the muzzle level and then the whole construction was lowered over the barrel to load the grenade in the muzzle. This quite complex operation made the gun more or less obsolete after introduction of the Type 4 20 cm and Type 4 40 cm rocket systems which were far easier to operate and to conceal.

The drawing also shows an AA-MG fork on the right of the crew cabin but I´ve never seen it mounted on a picture. There was no MG port in the cabin.

Four pre-series vehicles were built prior to the official introduction for test purposes. Serial production was cancelled at the same time the rocket launcher systems became operational.

My opinion: Too complex and too expensive for the given war situation of Japan in 1943/44. Systems like the Type 5 Gun Carrier Na-To or the Type 4 Tank Chi-To were far more needed than such a gun carrier.

Yours

tom! ;)
 

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