Soviet M1938 120mm mortar.

[davebender]

6km max range.
.....10.5 cm leFH 18/40 howitzer = 12km.
about 12 rounds per minute.
.....10.5 cm leFH 18/40 howitzer = 8.
Shell contains about the same amount of HE filler as a 105mm artillery shell.
285kg weapon weight.
.....10.5 cm leFH 18/40 howitzer = 1,955kg.

The 120mm mortar used by Germany and the Soviet Union looks very impressive on paper. How well did it perform in combat?

[Jabberwocky]

There is a very good write up of Finnish experiences with both Soviet 120mm and German 120 mm mortars here

FINNISH ARMY 1918 - 1945: 120 MM MORTARS

[davebender]

I'm surprised Germany didn't adopt that solution during 1935 when their army expanded from practically nothing to 36 divisions. It would have been a quick, inexpensive way to provide new infantry divisions with supporting artillery. When artillery production catches up with demand you can add some 10.5cm K18 weapons to each division for long range missions plus some of the heavier 15 cm sFH 18 howitzers.

[tomo pauk]

While the 105mm howitzers were a significant leap forward when compared with 75-77mm light guns from ww1, they were all requiring the capable motor towing in order to be efficient - weapon weighted far more, requiring more crew, ammo + charges being notably heavier, piece for piece. 105mm stuff was not able to be manhandled meaningfully, 120mm mortars could be manhandled. The cost of the mortar was indeed negligible when compared with 105mm howitzers.
Interestingly enough, with 120mm mortar at hand, Soviets went for 122mm howitzers.

[Shortround6]

The 120mm mortars were a great addition to a units firepower. However with a range of just over 1/2 the range of 105 howitzer they could not provide the deep support for an attack or help with counter battery duties.

[davebender]

That's why I suggested inexpensive 120mm mortars for general infantry support plus long range weapons like the 10.5cm K18 for long range missions. You get the best of both worlds. 120mm mortars can be pulled by almost anything. Two horse team, Kettenkraftrad and even the small 4WD VW Schwimmwagen would be adequate for towing a 120mm mortar cross country. Only the long range weapons would require artillery tractors.

How do the mortars compare with 10.5cm howitzers for accuracy and sustained fire ability?

[Shortround6]

Sustained fire there probably isn't much to choose. Accuracy of most WW II mortars is pretty bad.

The German 10.5cm howitzers weighed a bit under 2000kg in action, a bit more on the move. The 10.5cm K18 went over 5600kg in action and even more on the move. There were never going to be enough of them, especially considering that the 15cm s FH18 used the same carriage/recoil system. The 10.5cm K18 gun was a corp or army asset, it was not deployed on the divisional level.

A problem with the 12 cm mortars is not the weight of the mortar but in supplying them with ammo. A Russian M1943 mortar weighs about 500kg (1100lbs)on the move. The shells weigh about 35lbs each, bare without shipping containers/boxes. 32 unboxed bombs weigh more than the Mortar on it's wheels. The impact of the 12cm mortar bombs is certainly impressive but you are not going to keep them feed for very long without motor transport. a six tube battery firing 6 bombs per minute (under 1/2 peak rate of fire) for ten minutes will use up 6.3 tons of mortar bombs. Add in the shipping/transport containers and the logistics get real interesting.

[Tante Ju]

Mortars are effective for direct support. But have limitations.

However Shortrand point on ammo supply is very good. Also worth considering at what area a 10,5cm with double range can provide fire support immidate compared to a mortar, and how many more mortars you need to cover the same area with equal firepower.

I would say 3-4 times as many mortars (crews, logistics) and deep they cannot support.

[davebender]

Since 1914 German infantry have relied on 105mm howitzers firing danger close to defeat enemy attacks. That won't work if 120mm mortar accuracy isn't similiar to 105mm howitzer accuracy.

[Shortround6]

A study of the Modern (post 1995) US 120mm mortar. Wartime mortars from both Germany and Soviet union ( and any body elses smooth bores) is not likely to be as good, in fact they could be considerably worse. Mortars at the time were not only viewed as a "cheap" substitute for artillery, their ammunition was viewed as "cheap" to produce too. This lead to cheaper materials and more allowable variations or tolerances than allowed for in Artillery ammunition.

http://www.dtic.mil/ndia/2005smallar...rohanowsky.pdf

[psteel]

German infantry given the choice between infantry guns or mortars went for the infantry guns. Not only were they much more accurate, they had much more stopping power when it came to enemy AFV/vehicle assaults. As I recall when the move away from the infantry guns to mortars was proposed by 1943, it was expected to replace each infantry gun with two mortars to make up for the loss of accuracy.

[tomo pauk]

When the German Army was given such a choice? In one corner we have the lightest infantry gun (7,5cm), weighting 400 kg, able to propel the 6kg shell, and on the other corner we have the 120mm mortar weighting under 300 kg, mine weighting 2,5 times more, with range being 80% greater. Accuracy and stopping power vs. tanks with a shell fried at 210m/s is nothing to write home about; the traverse of 12deg also hampers firing vs. moving targets. Germans have had another choice, 105mm mortars, weighting 100 kg - 1/4th of the 7,5cm IG, range about the same, shell 20% heavier.

[psteel]

The decision to go to 'infantry guns' was done in the late 1920s under the first rearmament drive and there was no modern 120mm mortar for another 10 years.The design for the original german 10cm mortar began in 1934 and ended in 1939 leading to mass producion later that year.

During the war the 120mm mortar was to replace the 150mm infantry gun, the 82mm mortar was to replace the 75mm infantry guns....btw both these guns had HEAT rounds by 1941/42. The 105mm mortar was specifically designed to fire chemical shells and all such weapons were under special units.

Bit of reseach might have helped?

[Tante Ju]

Tomo, please for example tell me how you use a mortar to knock off a MG position in street fighting, when MG is on 2 level of 5 level building... just to illustrate in this case a IG is much better solution.

[tomo pauk]

Well, sure enough I wouldn't be driving any towed stuff into the street, the MG would've have a live fire exercise with the gun & it's crew. So, definitely not a plus for a towed IG.

The decision to go to 'infantry guns' was done in the late 1920s under the first rearmament drive and there was no modern 120mm mortar for another 10 years.

Thanks.
Saying that 'there were no modern' this or that is a moot point; there was no ground breaking technology that would've prevent a design & production of 120mm mortars, all the way between the world wars. All what was needed was Heer's requirement.

The design for the original german 10cm mortar began in 1934 and ended in 1939 leading to mass producion later that year.

There you go

During the war the 120mm mortar was to replace the 150mm infantry gun, the 82mm mortar was to replace the 75mm infantry guns....btw both these guns had HEAT rounds by 1941/42. The 105mm mortar was specifically designed to fire chemical shells and all such weapons were under special units.

There was nothing preventing the 105mm firing HE mines, and those were issued anyway. Stating in one sentence 'mass production' and on the other 'all such weapons were under special units' is contradictory.

Bit of reseach might have helped?

Of course, please do some research.