A history of the infantry gun in the U.S. (and elsewhere)

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The German army/armies improvised the concept of an infantry gun for knocking out pockets of resistance that survived artillery preparations. I wrote about that in an earlier post. The French did something similar, and eventually many countries employed relatively light guns for such purposes during the Inter-war Years.

Anti-tank guns, mountain guns and even light field cannons were imperfect substitutes for dedicated infantry guns in the direct fire role and Brandt-pattern mortars were imperfect substitutes for infantry guns in the indirect fire roles. So in theory, you could make do without infantry guns - and infantry guns were squeezed considerably by such competition.

The U.S. Army was a bit slow to catch up with the whole concept and was especially interested in the indirect fire role, as it seems. Its quite belated adoption became known as 105 mm howitzer M3.

In 1941, the U.S. Army requested a 105 mm howitzer suitable for carriage by air, and as a rough guideline, a weight of 2,500lb and a range of no less than 7,000 yards were stipulated. In response, the M2A1 howitzer was cut down in length by 27 inches, to become the Howitzer T7. The carriage of the 75 mm Howitzer M3A1 was adopted as a Carriage T6, and the recoil mechanism of the 75 mm Pack Howitzer, much modified, became the Recoil Mechanism 105 mm Howitzer T13. Surprisingly, when it was all put together it worked quite well and required very little further modification, and the design was standardized as the Howitzer M3 on Carriage M3 in February 1943. Trials of production models revealed a lack of strength of the carriage, so those converted from 75 mm matériel remained the M3, while a newly-manufactured design, with thicker metal in the trail, became the M3A1. [...] 2,580 were built [...].

(Ian V. Hogg "British and American Artillery of World War Two", 1978)

105 mm M3 Howitzer in action, WW2

 

These guns - eventually used as a kind of medium infantry gun since there weren't even remotely enough airborne troops to make use of such a production run, were a moderate success. The Army didn't exactly fall in love with them. U.S.Army field artillery of the time was a huge fan of multi-battalion "time on target" fire missions that united the firepower of many batteries, while infantry guns lack the range to be available for this and are inherently rather point target destruction tools for commanders below division level (that would be battalion or "Combat Command" a.k.a. brigade in the WW2 U.S.Army).

There was a lot of competition as well. Mortars, recoilless guns, bazookas, artillery, on-call fighter bombers and most of all a huge quantity of Sherman tanks in direct cooperation with infantry.

There's also the possibility that the U.S.Army knew about infantry guns, but didn't understand them.

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You might think that this was the end of the American infantry gun story, but there's a funny twist. One hand didn't exactly understand what the other did, and the Marines re-invented the wheel. The M3 Howitzer was - as the quote showed - a 105 mm howitzer (rifled barrel) on a modified 75 mm pack howitzer (=mountain gun) carriage.

The Marines - being Marines and all, but most importantly different - had post-war the glorious idea that their 4.2" mortar could be mounted on a carriage. A modified 75 mm pack howitzer carriage. Yeah, THAT 75 mm pack howitzer carriage.

4.2" M30 mortar in action in Korea, 1952

Well, the 4.2" mortar was an unusual one - it had rifling just like a howitzer. Most mortars have smooth-bore barrels.

Let's see - 4.2", what's that in millimetre? 107 mm. Interesting.
What was its range? 7,400 yards as a mortar.

Well, that's only a coincidence! ;)

The Marines being Marines and innovative and all did some PR. They didn't call this bastard gun a howitzer. No, they called it M98 Howtar ("Howtar" being an unofficial designation).

 Ain't that funny?

(The Marines became actually innovative afterwards, but that was not exactly a success.)

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Meanwhile (or actually slightly after the M3 Howitzer), German engineers thought hard about an improvement of the infantry gun idea. They combined mortar-ish hardware with a gun-ish carriage as well.

They had the idea for the High-Low pressure system in which the propellant has first some volume for expansion (into a lower pressure state) before the projectile begins to move much. This allowed for a much lighter (but longer) barrel and a lighter carriage.

Everything had to be done in great haste, so the projectile of a 81.4 mm mortar and the carriage of the semi-obsolete 50 mm anti-tank gun were married with (afaik) the muzzle brake of a 75 mm anti-tank gun and, well, what else a gun needs. There was a shaped charge version of the shell and some experimentation with a purpose-built very light carriage, too.

8 cm PAW 600 a.k.a. PWK 8H63, true calibre: 81.4 mm (smoothbore)

This gun did not have a great maximum barrel elevation (only 32°), but it combined light infantry gun weight, reasonable effective range and penetration in the important anti-tank role and a reasonable performance in the indirect fire role (out-ranging the common 81.4 mm mortar by much and being about on par with the other regimental indirect fire asset, the new 120 mm mortar).

It's still amazing that it was a quite accurate weapon despite launching a subsonic mortar bomb with an according made-for-subsonic shape with a muzzle velocity of 520 m/s (about Mach 1.5).

The USMC re-invented the Army's M3 Howitzer / medium infantry gun, but the Bundeswehr failed to get the high-low pressure guns (there was also a 100 mm model), too. Instead, recoilless guns were in fashion during the mid-50's (moderately practical, but even cheaper than a high-low pressure gun!) and later on there were the first generation anti-tank guided missiles that finally evolved into practical munitions.

Those were in turn replaced by second-generation anti-tank missiles which were more practical, but with a distinct survivability drawback.

Now guess what was fired in anger against Argentine field bunkers in 1982 during the re-conquest of the Falklands, in best WW1 infantry gun fashion ...

BTW, those 2nd generation ATGMs (with typical SACLOS guidance) were in turn replaced elsewhere with more modern ones, and Hezbollah used those against Israelis troops pinned in buildings during the 2006 Lebanon War.

The infantry gun thing keeps bouncing back.

S O

edit 2016-11: A related (old) article in a South African military journal, pp.47-50. I suspect the author is Russian (judging by spelling certainly not American or British, so it wasn't Storr). The described D-395 gun design would be interesting for 3rd World ground forces if it is fully compatible with standard munitions.

Also, see this about infantry guns today.

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