Kill rate of German SP guns

[JasonC]

In addition to cheaper, the more important consideration was that a larger gun could be mounted on the same chassis as a turretless AFV than as a turreted one. The switch to SP guns went hand in hand with the upgunning of all early war lighter tanks.

- The Pz I chassis was used in midwar as a chassis for 47mm SPAT with open tops. 2 7.92mm MGs or a 47mm gun? 6 times the gun caliber. Once the 47mm was too small to be useful, these were phased out altogether - the only German chassis to see production actually halted.

- The Pz II chasis was used for long-75 Marders and for 105mm Wespes. Instead of a turreted 20mm gun and MG, big guns, no turret, and opened topped. 3-5x the gun caliber.

- The Pz38 chassis was used for long-75 Marders, 150mm sIG "Crickets", and armored long-75 Hetzers. Up from a turreted 37mm, so 2-4 times the gun caliber.

- The Pz III chassis was used for StuG and StuH with long-75 and 105. Up from initial 37mm, and the largest turreted weapons 50L60 and 75L24. This change took the longest time, because the Germans were reluctant to change their main vehicle chassis to turretless, and because the older guns remained at least somewhat useful into midwar.

- The Pz IV chassis was mostly used for turreted long-75 guns of course. And became the main type precisely because it could accept that gun in a turret. But the chassis also handled larger guns in SP mounts - 88L71 Nashorns, 150mm Hummels both open-topped, 75L70 in later Jagdpanzers, and short 150mm in Brummbars, both also heavily armored compared to the standard Pz IV.

- Comparatively little use was made of upgunned SPs with the heaviest chassis, since they remained highly effective in turreted form. But the 88L71 on Jagdpanthers is bigger than the 75L70 on turreted Panthers, the same on Elephants is longer than the Tiger Is gun, the 128mm on the Jagdtiger is bigger still.

So basically, the point was you could get a larger, more powerful gun on the same chassis, more cheaply. In the case of the smallest chassis this was particularly important, since the turreted versions became nearly useless as armor thickness on the fielded fleets increased. Particularly once the Russians were through with 45mm light tanks, and their fleet transitioned to almost all T-34s, the 50mm and smaller guns weren't sufficient for main battle tanks.

The alternatives were then to suspend production of smaller chassis, or upgun them as SP guns without turrets. The Germans could not afford to lose running chassis production lines, as this would mean fewer AFVs produced. They struggled longest with the Pz III transition, trying to fit a useful gun into a turret. But once committed to the StuG it became the most common SP type, since it inherited the most common early war chassis lines.

Using them, they found they had other virtues, like a low sillouette which favored ambush tactics from concealed positions. The absence of a turret was not felt too keenly when defending, especially when combined with use of cover in keyhole sighting techniques. But the initial logic of it came from the production side, from the need to keep the older and smaller lines running to generate enough useful AFVs.

[Tero]

Originally posted by JasonC:

the SP guns only about 1/3rd of the total, roughly matched by each of the other two main types (Pz IV and Panther I mean).

1/3 SP, 1/3 PzKw-IV and 1/3 Panther or 1/3 SP, 1/3 PzKw-IV and Panther and 1/3 others (PzKw-III/Tiger/35(t),38(t)) ?

Production figures from http://www.feldgrau.com/afvstats.html

(entire war)

SP AT guns 2 545

TD 5 363

AG 10 550

SP total 18 458

all turreted gun tanks 29 910

1940

SP AT guns 173

TD 0

AG 184

SP total 357

all turreted gun tanks 1512

1942

SP AT guns 835

TD 0

AG 789

SP total 1 624

all turreted gun tanks 4281

1944

SP AT guns 456

TD 3400

AG 4999

SP total 8 855

all turreted gun tanks 7975

Ergo, the tanks are living longer than the SP guns.

A force commander might be disposed to pulling out his turreted tanks and leaving the SP guns to cover the retreat. Or in attack the infantry might be supported directly by their organic SP's instead of tanks. Being artillery does mean that a armoured force might be more willing to sacrifice assest not directly under their care. But please look below for loss stats that do not comply with your conclusions.

Because the tanks are fielded in much larger groups than the SP guns. They fight in mobile divisions, which are more survivable overall, less likely to be overrun, better equipped with supplies and spares, etc.

In contrast: more likely to be forced to execute long road marches from one crisis spot to another = more basic maintanance required. Also more likely to find itself on unfavourable terrain.

Whereas, 10 StuG as one company of a divisional AT battalion in a Heer infantry division, are seperated from support, committed in tiny numbers, etc.

The support being denied is what ? Arty ? Each Heer infantry division had it. Infantry ? Each Heer infantry division had it. (Duh ! ) There were also towed AT guns in the Heer infantry division OB so they could rely on some support from there too. Being commited in tiny numbers is not necessarily a bad thing in tactical terms, even if it can prove to be a logistical nightmere. Also, the Stugs were organized in separate battalions of 27 or 31 vehicles or brigades of 45 vehicles (corps and army level formations) so their deployment was not necessarily just that 10 vehicle penny packet.

They may benefit from defensive use (both can, but they may be more likely to - fine). But that is not as big a deal as being part of a Panzer division or corps, with hundreds of AFVs. Where the tanks appear on the front in more concentrated doses, it makes sense that each vehicle will have a longer lifespan, even if it gets fewer unique opportunities (per unit time) to kill enemy AFVs. And the production vs. fleet strength comparison bears that out.

When the data from http://www.feldgrau.com/afvstats.html is combined with data from

http://www.freeport-tech.com/WWII/011_germany/999_AFV_losses.htm

your comparison becomes questionable.

PzKw-III losses in 1943 - 2 395

PzKw-III production in 1943 - ~235

PzKw-IV losses in 1943 - 2 352

PzKw-IV production in 1943 - 3 013

total production 3 248 vehicles

total losses 4 747

net loss in 1943 1 499

StuG III losses in 1943 - 1 566

StuG III production in 1943 - 3011

net gain in 1943 1 445

In 1943 925 SP AT guns were lost and 1 227 built.

In 1944 the Germans lost 3 555 Stugs and 5 748 turreted tanks while they built 4 999 Stugs and 3 400 TD's ( lost 412) and 456 SP AT guns (lost 1 155 - 1943 production 1 227) and 7 975 turreted tanks.

Lookind at the 1941-45 loss figures and comparing them to I would say the SP's fared better than the turreted tanks. Overall. The SP AT guns did get punished but the Stugs seem to have been better. Speaks volumes for the benefits of enclosed fighting compartments.

[Redwolf]

Tero, I'm afraid your number have a weakness. The number of losses obviously depends on the number of existing vehicles.

However, you compare 1943 losses against 1943 production, not 1930-1943 production minus 1930-1942 losses.

I hope to find the time to come up with data without this weakness using my loss rate accounting stats. However I have difficulties finding data about existing Jagdpanzer IV or Hetzer. I have numbers for turret AFVs (Jentz Panzertruppen) and StuGs (Spielberger's StuG book). However, for the light TDs I only find data which is only for one theatre or otherwise flawed. Any hints appreciated. We need (complete) losses in one year or the number of existing vehicles. For the Jagdpanzer and Hetzer we need data with more resolution that a year.

[JasonC]

By "support" I meant rear area support - maintenance, spare parts, POL, recovery, etc. It takes an organization to keep AFVs in working order, and one of the main drawbacks of penny packet deployments is it seperates most of the vehicles from these necessarily centralized forms of support.

A Panzer division (or corps) can provide a lot more support to keep its vehicles running, and get them back into action, than the 1st company of a divisional PZ Jgr Abt, or a seperate battalion sized unit of StuG. And StuG were definitely used in packets as small as 10 vehicles - any number of real world OOBs will show you that. Even StuG brigades (which are only battalion sized, only called brigades because of the artillery size designations) were often called upon to support more than one unit at a time, resulting in the same situation - companies operating on their own for significant combat periods.

As for the early war figures, I don't think they say anything about the subject I was discussing. The Germans made heavy use of turretless SP guns only from 1943 on, and in that year the fleet was transitioning to the turreted and SP mix. Losses come out of existing fleet strength, not just the year's production, and existing fleet strength of SP guns really took off only in 1944. I know the production figures, and you really don't add anything by quoting them over again.

The ordinary course of a "product transition" is that production is initially far above losses, because losses are low. Losses are low because there aren't many in service. As the number in service rises, so does the loss rate. This continues until the loss rate catches the rate of production, though the changes in fleet size become marginal well before the actual peak of vehicles in service. When a type is replaced, the losses continue without production, drawing down the fleet strength, until the type becomes insignificant - thus completing the cycle.

In 1943, Pz III production was all switched to making StuGs (Alkett switched over back in 1942, the rest by early 1943). The Pz III was still the dominant type in the fleets at the begining of that year, and had been since the fall of France. By Kursk the Pz IV long had replaced it as the main type, though only about half the fleet were that type, and about 1/3rd were still the earlier mix.

Another way of putting it is that about 10,000 of the turreted tanks in your figures are from the early war, when only a handful of SP guns were being used. In the second half of the war, their were around 20,000 of each type, turreted or not turreted.

If you want to see the point I was making about SP gun longevity, you have to look at 1944 and afterward, when SP guns were a large part of both the existing fleets and of production, just like the turreted varities. And you have to look at fleet strengths. There were about as many later SP guns (StuG, StuH, TD, SPAT) as later turreted tanks *made* (around 20k each). But there are not as many SP guns in the unit returns in the late war. Instead you see, as I said, around 1/3rd Panther or better, around 1/3rd Pz IVs, and around 1/3rd SP guns of one kind or another - mostly StuG. 1944 to the end. Nobody is talking about turreted Pz 38s by then.

How did they get that way? Why weren't there twice as many StuGs or Jagds in unit strengths, as each of Panthers or Pz IVs? (As many as both combined, in other words). Through the end of 1944, 7000 Pz IVs with long 75s had been produced, and 5500 Panthers. StuG&H production by then was 10000, and Jagds and Hetzers another 3000. If each was lasting as long in action, the fleet should have been split 50-50 between these main late-war types. It wasn't.

[JasonC]

Also, there is a bit of a problem with your idea of an "overall" "how they fared". The Germans lost the war, and by the end of it that means they lost everything they made - KOed, broken down, captured, whatever. You cannot get any meaningful info by aggregating the whole war, certainly not about average vehicle lifespan, which is the subject under discussion. Because "in the long run we are all dead", as the saying goes. The question is whether this or that part of the armored fleet-in-being during the war (not after it - there wasn't one) required a larger or smaller production stream to maintain a given level of fleet strength.

In the second half of the war, the overall production streams for tanks and SP guns were the same overall size, and the turreted production was "front-loaded" (higher relatively in 1943 than in 1944). Meaning the same number of vehicles saw action, and the turreted ones on average saw it longer. If they all lived the same length of time, the turreted ones should have been marginally *less* common than SP guns by the end of 1944. The same number had been made (roughly, for the main types it is accurate enough, ~13K each), and a larger portion of the turreted tanks was older.

So, why weren't turreted tanks scarcer than SP guns by late 1944? When you go look at unit returns in 1944, middle or late, you see about 30-40% SP guns and about 60-70% turreted tanks. How did they get that way?

[Tero]

Originally posted by redwolf:

Tero, I'm afraid your number have a weakness. The number of losses obviously depends on the number of existing vehicles.

However, you compare 1943 losses against 1943 production, not 1930-1943 production minus 1930-1942 losses.

Only because the losses source starts counting from 1941 and the Stug's came into service in a big way in 1943. Also, most of the earlier tanks were lost or converted to other uses by 1943.

Prior to 1941 the Feldgrau source counts 4 941 turreted tanks manufactured. 1941 production was 3 094 while losses were 2 262. The 1942 production was 4 281 while the losses were 2 546.

In 1942 Stug losses were 330 while the production up to and including 1942 numbers 1 521 vehicles. Prior to and including 1942 the production of SP AT guns numbered 1 609 while the losses in 1942 were 127.

The clear trend from 1943 onwards was more SP, less turreted tanks. And the losses were more severe for the turreted tanks than for the SP's. They made less turreted tanks and they lost them faster than they made them while the SP production could keep the production ahead of the losses.

I hope to find the time to come up with data without this weakness using my loss rate accounting stats.

I hope to find the loss data for the eraly years.

Any hints appreciated. We need (complete) losses in one year or the number of existing vehicles.

Concur. If the loss data starts counting from June 1941 (and not 1944 as the * indicates) the losses can be for the Eastern Front alone for all I know. But the data is an indication anyway.

[Tero]

Originally posted by JasonC:

Also, there is a bit of a problem with your idea of an "overall" "how they fared". The Germans lost the war, and by the end of it that means they lost everything they made - KOed, broken down, captured, whatever. You cannot get any meaningful info by aggregating the whole war, certainly not about average vehicle lifespan, which is the subject under discussion.

I got to love the way you guys never fail to pull out the "they lost the war" card every time your reasonings in in jeopardy of getting bogged down.

So, why weren't turreted tanks scarcer than SP guns by late 1944? When you go look at unit returns in 1944, middle or late, you see about 30-40% SP guns and about 60-70% turreted tanks. How did they get that way?

Because Stugs were artillery, turreted tanks armour ? The Stugs in armoured formations got counted in while the ones in Stug Brigades were not counted as armour but artillery ?

Can you give any specific numbers ?