US light tanks derivatives: how would you do it?

[parsifal]

I am a little bemused by the discussion at this juncture. So i apologize if my comments arent quite on topic.

Tracked SPGs for the Soviet army using indirect fire weaponary would have been somewhat of a waste in an offensive role. I know they had tracked artillery, but this was either of the direct fire variety, or was never meant to operate as mobile artillery, in the sense the artillery would move during the course of a battle. Soviet indirect artillery was always fixed, in the sense that it would be moved into position, alsong with awhole bunch of other artillery pieces, have its artillery stocks built up over a series of weeks or months. When the time came, this artillery would unleash its ammunition load, and then wait until the artillery pieces were moved to the next firing position. Soviet artilery was great on firepower, but weak on flexibility, meaning Soviet Command Control was simply too inflexible to manage a mobile artillery park.

The artilery that did accompany the fire support formations was generally of the direct fire variety. It usually shot at targets it could see. this is not really true artillery in my book. A howitzer or similar would not do for this sort of work. Soviet gunners were simply not flexible enough to be able to quickly work out indirct firing solutions quickly.

 

[tomo pauk]

The usage of towed artillery in order to achieve breakthrough is logical. But what happens when tanks try to exploit the breakthrough? Within 3 hours the tanks can be 50-100 km behind enemy lines; we can assume they travel part road, part off-road, with sporadic fighting. And then, the tanks are stripped of indirect fire support, since it takes at least 1 hour for towed pieces to mount + dismount, plus they're hampered more by terrain than tanks.
The same level of flexibility can be expected for counterattacks.
The case that involves light tanks acting as spotters for SP artillery is not that fetched, even if we take Soviets' lack of flexibility into account.

Using a direct-firing artillery to clear known/suspected AT artillery emplacements invites the return fire (I know that we except from Soviets to not take care on that - still not the healthiest approach). The indirect-firing support don't need to be driven to the sights of enemy guns, and if it's in SP form it can stop, fire move before enemy can do the counter-battery fire.

 

[Shortround6]

I am a little bemused by the discussion at this juncture. So i apologize if my comments arent quite on topic.

They are some what on topic. SP guns are not always superior to towed guns. SP guns actually have several different functions. Some SP guns just provide a tracked chassis with more a bit better mobility in bad terrain. They may actually offer slower movement than a towed gun on good roads or need rail transport for long moves. Some SP guns offer armor protection to their crew. This varies enormously from things like the early Stugs and Russian SU-122.
http://www.achtungpanzer.com/images/su122.jpg
To things like the American M-12
File:155mm-GMC-M12-France-1944.jpg - Wikipedia, the free encyclopedia
where most of the ammo and a good part of the gun crew was carried in a separate vehicle and the crew served the gun while standing in the open just like a towed gun. The M-12 did have the ability to fire, move a few miles and fire again in much less time than a towed gun but to make use of that capability required the previously mentioned maps and survey teams (new firing position already surveyed) along with a communications net (not just radios in the vehicles) and command structure.
Artillery often used up enormous amounts of ammunition, unless you have vehicles that can supply the SP guns they will run out of ammo rather quickly with just the on board stocks. This why the Germans not only had one spare chassis per Wespe battery but even early Stug batteries had Sd Kfz 252's (with trailers) attached and had Sd Kfz 253's as forward observer vehicles, the Stugs apparently, weren't quite the up front,in the enemies face many war gamers believe. While they could do it, it seems the batteries (note the word batteries instead of platoon or company) were certainly equipped for a more traditional artillery role of standing back a bit and providing covering or support fire from a distance that includes being out of the line of sight.

Another thing to note about SP guns is that while towed guns had larger crews the difference in numbers wasn't just to manhandle the gun. It is one thing to have a SP anti tank gun with one piece ammunition. Take the rounf from the rack and throw it in the breech and go BANG! It is another thing to feed a howitzer with what is really 3 piece ammunition. The HE shells are not normal stored or transported with fuses in place. The propelling charges are normally carried in the case and the appropriate charges removed for the range desired. This means you need men and working space near the gun so that a supply of fused, charge adjusted ammunition can be fed to the actual crew member/s loading the weapon. Other wise the rate of fire suffers.
The American 105mm howitzer was rated at 3 rounds per minute sustained fire. Please note that is 20 minutes for an M7 with a few rounds left over but they may be smoke or AP. Please also note that a crew member/s if they haven't prepared ammunition in advance have to take the projectile from the rack/storage, take out the transport plug from the fuse well, un-box a fuse and screw it into the fuse well, take the case from a rack/storage box, take the shipping plug from the cartridge case mouth, pull the required number of charges from the case if not firing at max charge and then put the projectile in the case for loading as a semi fixed round. With a towed gun there are plenty of extra hands to do this. It may be a reason the M7 had a 7 man crew, Commander, driver and 5 man gun crew. Shrinking the vehicle may mean shrinking the crew and along with a smaller ammo supply on board means a lower rate of fire.
As far as SP guns in the Pacific, do you really need an SP gun when some of the islands were of a size where if the gun got onto the beach it could hit the other side/end of the island without being moved?
SP guns are also going to need bigger landing craft that towed guns and/or more of them.
as far as jungle use goes, there were several projects to reduce the size/weight of towed guns or the replacement of towed guns by large mortars. Trying to move SP guns through the jungle may have been much more trouble than they worth.

 

[Shortround6]

"The case that involves light tanks acting as spotters for SP artillery is not that fetched, even if we take Soviets' lack of flexibility into account."

yes it is. WW II radios were not very sophisticated. Tank radios were often short ranged and operated on different frequencies than the artillery radios. The radios could be tuned to a number of different frequencies but it some times took a number of minutes to change/tune to the new frequency. Command tanks (and forward observer vehicles) often had extra radio sets so they could rapidly switch which "radio net" they were talking on. While a light tank might be equipped to act as a spotter (forward observer)not every light tank was equipped to do so and certainly not every tank commander trained to do so.

 

[tomo pauk]

They are some what on topic. SP guns are not always superior to towed guns. SP guns actually have several different functions. Some SP guns just provide a tracked chassis with more a bit better mobility in bad terrain. They may actually offer slower movement than a towed gun on good roads or need rail transport for long moves. Some SP guns offer armor protection to their crew. This varies enormously from things like the early Stugs and Russian SU-122.
http://www.achtungpanzer.com/images/su122.jpg
To things like the American M-12
File:155mm-GMC-M12-France-1944.jpg - Wikipedia, the free encyclopedia
where most of the ammo and a good part of the gun crew was carried in a separate vehicle and the crew served the gun while standing in the open just like a towed gun. The M-12 did have the ability to fire, move a few miles and fire again in much less time than a towed gun but to make use of that capability required the previously mentioned maps and survey teams (new firing position already surveyed) along with a communications net (not just radios in the vehicles) and command structure.

Both allies axis forces used successfully SP artillery in indirect support role as early as late 1942. So, even while I agree with paragraph above, the real usage of SP arty was proven as feasible and efficient.

Artillery often used up enormous amounts of ammunition, unless you have vehicles that can supply the SP guns they will run out of ammo rather quickly with just the on board stocks. This why the Germans not only had one spare chassis per Wespe battery but even early Stug batteries had Sd Kfz 252's (with trailers) attached and had Sd Kfz 253's as forward observer vehicles,

If Allies have had anything in supply, that would be vehicles. Both for recon work and as parts of logistics system. Germans can do it, Allies even better.

the Stugs apparently, weren't quite the up front,in the enemies face many war gamers believe. While they could do it, it seems the batteries (note the word batteries instead of platoon or company) were certainly equipped for a more traditional artillery role of standing back a bit and providing covering or support fire from a distance that includes being out of the line of sight.

StuGs were capable of both direct fire and indirect. For indirect fire to be efficient they require radios. The sophistication of Western Allied radios is on par with sophistication of German gear.

Another thing to note about SP guns is that while towed guns had larger crews the difference in numbers wasn't just to manhandle the gun. It is one thing to have a SP anti tank gun with one piece ammunition. Take the rounf from the rack and throw it in the breech and go BANG! It is another thing to feed a howitzer with what is really 3 piece ammunition.

That's okay.

The HE shells are not normal stored or transported with fuses in place. The propelling charges are normally carried in the case and the appropriate charges removed for the range desired. This means you need men and working space near the gun so that a supply of fused, charge adjusted ammunition can be fed to the actual crew member/s loading the weapon. Other wise the rate of fire suffers.

(while I know ordinary arty works somewhat different)
I served on Praga V3S, SP AAA vehicle, that had 2 x 30mm onboard. Time to convert from standing still to have gun charged ready to fire was 80 seconds.
The 2 batteries of our AA regiment have had towed 3x20 mm guns. Their time to be ready to fire was some 5 minutes; 3 times more than we needed, Despite having crew of 8 (we have had 5, only 2 loaders preparing the gun) and having ammo drums 6 times lighter.
(back OT)
With 1 shell every 20 seconds, 2 trained loaders one aimer can tell jokes and still hit their targets.

The American 105mm howitzer was rated at 3 rounds per minute sustained fire. Please note that is 20 minutes for an M7 with a few rounds left over but they may be smoke or AP. Please also note that a crew member/s if they haven't prepared ammunition in advance have to take the projectile from the rack/storage, take out the transport plug from the fuse well, un-box a fuse and screw it into the fuse well, take the case from a rack/storage box, take the shipping plug from the cartridge case mouth, pull the required number of charges from the case if not firing at max charge and then put the projectile in the case for loading as a semi fixed round. With a towed gun there are plenty of extra hands to do this. It may be a reason the M7 had a 7 man crew, Commander, driver and 5 man gun crew. Shrinking the vehicle may mean shrinking the crew and along with a smaller ammo supply on board means a lower rate of fire.

Wespe was managing with 5 men. For dealing with on-board ammo more than enough. In M3/105mm as I've proposed one extra crew member is located next to driver.

As far as SP guns in the Pacific, do you really need an SP gun when some of the islands were of a size where if the gun got onto the beach it could hit the other side/end of the island without being moved?

Never said 'Pacific'. Always 'Asia/Pacific'.
Plus, we have New Guinea campaign dragged into 1945. Then Philliphines campaign, Okinawa battle (almost 3 months).

SP guns are also going to need bigger landing craft that towed guns and/or more of them.

As far as space needed for SP vehicle vs. truck + gun, SP vehicle needs less of it.
As far as weight goes, landing crafts were better suited for heavier smaller stuff, than for bulkier lighter stuff. From Wiki, about LCT of Royal Navy:

5 × 30-ton or 4 × 40-ton or 3 × 50-ton tanks or 9 trucks or 250 long tons (254 t) of cargo

250 tons means 16 x 15 ton vehicles (we don't have space for that, of course), but there is only space for 9 trucks, even less when we cram some guns there too.
So we actually save space.

as far as jungle use goes, there were several projects to reduce the size/weight of towed guns or the replacement of towed guns by large mortars. Trying to move SP guns through the jungle may have been much more trouble than they worth.

Wherever tanks were used, SP arty could too.

 

[parsifal]

Some interesting comments here am particulalry interested in the comments about the usee of SPGs in the Jungle. One of the biggest tactical mistakes made by the allies was to assume pre-war that tanks could not operate in the Jungle. The japanese were the pioneers in this regard, with considerable armoured assets deployed into malaya, Burma and new Guinea that I know of. Their armour was not particularly good and suffered accordingly, but it was still considered to be of enormous benefit.

The Australians were the first army in the Pacific that used armour to any significant extent. At buna and Gona, Stuarts were used for Infantry support and to destroy Japanese strong points. In this instnace the armour was placed in front of the infantry, because ther was a greater threat to the infantry thaan there was to the armour....ATGs were uncommon in the Jungle.

I am unaware of any significant use of SPGss in the Jungle, though I do know this occurred in Vietnam. Once again, drawing on my own countries experience, Centurions were used to great effect in Vietnam in the 60s. Doubling back to the pacific, we also deployed Matildas to Bougainville, and Borneo in 1945.

However, saying that mortars were a satisfactory substitute for tube artillery in the Jungle is incorrect. The allies fought at a considerable disadvantage in the mountainous jungles of NG because at the beginning they had to rely on mortars for artillery support. The Japanese had their 70mm Infantry guns and 75mmmountain guns that completely outclassed the allied artillery support until firstly the japanese ran out of ammunition, and secondly, after the Australians beganpainstakingly manhandling their shortened 25 pounders into the junglle battle areas. Even so, the Australians had great difficulty with their 25 pounders because of the weight issue. The US 75mm Pack howitzer was another solution to this problem.

I dont see an inherent reason why tracked SPGs could not be deployed into the jungle. having tracks and their own propulsion would have made it easier, not harder to deploy, surely. The right vehicle, which emphasises mobility, and lightened the payload, would have don the job quite well IMO.

 

[Shortround6]

Never said 'Pacific'. Always 'Asia/Pacific'.
Plus, we have New Guinea campaign dragged into 1945. Then Philliphines campaign, Okinawa battle (almost 3 months).

I would say that Okinawa rather proves the point. Okinawa being about 60 miles long and the battle taking 3 months I would say the presence or absence of SP guns made no real difference to length or out come of the battle.

As far as space needed for SP vehicle vs. truck + gun, SP vehicle needs less of it.
As far as weight goes, landing crafts were better suited for heavier smaller stuff, than for bulkier lighter stuff. From Wiki, about LCT of Royal Navy:

5 × 30-ton or 4 × 40-ton or 3 × 50-ton tanks or 9 trucks or 250 long tons (254 t) of cargo

250 tons means 16 x 15 ton vehicles (we don't have space for that, of course), but there is only space for 9 trucks, even less when we cram some guns there too.
So we actually save space.

All well and good if you have LCT's, Not so good if you have LCVP's and early LCM's. It is possible to get a 105 towed gun ashore in a DUKW, but then you have to get the gun out of the DUKW
Try sticking a Stuart in a DUKW

 

[tomo pauk]

Okinawa can prove many points, but not the one that SP gun is not of any use in Asia/Pacific.

By 1943 there were plenty of LCs capable to carry one or more 15-ton vehicles; a vessel that can carry one M4 tank, can carry 2 x M3s or derivatives.
Infantry can ride in their DUKWs all day long