Disadvantages of a flat trajectory

[SteveP]

This question is primarily for the grogs, I think, since if my interpretation is correct, there is probably no relevance to gameplay in CM.

The question is inspired by a report from an American staff officer during the Tunisian campaign. It concerned the early "tank destroyers" (e.g., the M-3). The report concluded that these AFVs could not conduct offensive operations, for many reasons (like thin skin, for one thing). But in particular, according to this officer, because they could not deal with AT guns -- and this was because their own guns had a "flat trajectory." This puzzled me for awhile, but then I thought of a possible explanation.

I surmise that the problem was that in these AFVs the guns had no elevation capability, and therefore could not be used in howitzer mode, to fire at long range and/or from defilade. Does that sound like the right explanation for the above comment?

If this was in fact the problem, then:

1. Was this not common for tank destroyers and mobile assault guns generally?

2. Was it standard doctrine to use indirect fire (if all you had were AFVs) to silence AT guns -- rather than the keyholing tactic, which is about all we have to work with in CM?

[JonS]

Flat traj is good for hitting vertical targets.

Arced traj is good for hitting flat (or area) targets.

Basically, you want the rounds coming in normal to the target.

[John Kettler]

SteveP,

A dug-in antitank gun, unless we're talking the classic 88 with tall shield, presents a tiny vertical and horizontal profile. A miss short must be close to do much of anything, and a miss long may be off by hundreds of meters or more. Lower velocity weapons with arcing trajectories are more forgiving of range estimation errors and are trying in essence to hit a larger target. This is why the on board mortar is the best gun killer in the CM games. It can be aimed with fair precision, and because of its near vertical trajectory, maximizes the kill zone around the gun.

Regards,

John Kettler

[SteveP]

Jon and John: Your comments are along the lines of my first thought -- which only left me more puzzled. Why single out the M3 (called a "support halftrack" in CM) for it's flat trajectory, when it actually has a relatively low shell velocity. The only thing I could think of was that the staff officer was really commenting on an inability to get any elevation from the gun.

Maybe it's too much of a leap on my part to assume that implied a doctrine of using indirect fire. On the other hand, it seemed obvious to me that these thin-skinned AFVs could not have engaged in direct fire with AT guns in any event -- so worrying about the trajectory of the shell as it left the muzzle would seem rather pointless, like commenting about the food service on the Titanic. In other words, I'm assuming that the officer's comment (he had some responsibility for planning/training in the use of tank destroyers) wasn't pointless.

And yes, I know that mortars are the desirable way of knocking out guns. But we also know that HE equipped AFVs also routinely knock out AT guns (in CM, at least) as long as they are keyholed, or in an overwatch situation.

[pamak1970]

Originally posted by SteveP:

Maybe it's too much of a leap on my part to assume that implied a doctrine of using indirect fire. On the other hand, it seemed obvious to me that these thin-skinned AFVs could not have engaged in direct fire with AT guns in any event -

That is my opinion also .

This seems to be more about combined arms warfare than ballistics and probabilitites of kill.

It is essential especially in offensive operations to have means for indirect fire to counter AT defence and a great mobility to keep up with the pace of operations.

As the combined arms force gets close enough to the enemy making indirect fire support impossible,it will be the infantry's job to assist armour against AT guns while armor "returns the favor" assisting infantry against MGs.

[ August 12, 2006, 04:24 AM: Message edited by: pamak1970 ]

[Michael Emrys]

Originally posted by SteveP:

I surmise that the problem was that in these AFVs the guns had no elevation capability, and therefore could not be used in howitzer mode, to fire at long range and/or from defilade. Does that sound like the right explanation for the above comment?

That has to be false since they were used in Italy, especially by Commonwealth troops, in the indirect fire mode.

Michael

[pamak1970]

I think SteveP implies a limited elevation capability which still restricts the effective employment of the weapon in indirect support adding among other ristrictions engaging enemy positions in defilated positions ,reverse slope and so on.

[Brent Pollock]

Hmmm...that angle doesn't look terribly steep. It doesn't say "we're using plunging howitzer fire" to me. It looks more akin to the use of Shermans & M-10s in indirect fire mode. In those cases, to get something closer to plunging fire, they drove the vehicle onto some form of incline.

[John Kettler]

Okay, I just learned something new. The famous French 75, which is what the TD in question is armed with, has a maximum elevation of only 18 degrees. Figured it could go a lot higher than that, but its range was only 11,110 meters in consequence. Source is page 137 of THE ENCYCLOPEDIA OF WEPONS OF WORLD WAR II, Chris Bishop, Editor.

Regards,

John Kettler

[SteveP]

Interestingly, I just read an account where US TDs (my guess is that we are talking about M10s now) were used effectively in direct fire against AT guns, at a point near the end of the Tunisian campaign. However, this account implies that the TDs may have been firing from atop a ridge line. Or the M10 may have had a better gun for that purpose than the M3. So, I'm still unclear as to whether the M3 gun was unusually handicapped, or (to be provocative for a moment) CM should do a better job of modeling the limited effectiveness of flat trajectory guns when the target is dug-in.

[Michael Emrys]

Originally posted by Brent Pollock:

Hmmm...that angle doesn't look terribly steep.

It's not. This site lists maximum elevation as 29°. It is, after all a gun and not a howitzer. Still could be used for indirect fire though. For plinking ATGs, depends on how the ATG is sited, but in most cases they should at least be able to raise the anxiety level of the crew without exposing themselves to return fire.

Michael

[Michael Emrys]

Originally posted by John Kettler:

Okay, I just learned something new. The famous French 75, which is what the TD in question is armed with, has a maximum elevation of only 18 degrees.

Actually, it was armed with the M1897A, which was a modified version of the 75. In the process of modification, the maximum elevation may have been substantially increased, but we haven't nailed that down yet.

Michael

[Michael Emrys]

Originally posted by SteveP:

Or the M10 may have had a better gun for that purpose than the M3.

It was higher velocity, which means an even flatter trajectory. But I think it carried a smaller HE payload.

I think the big problem of the M3 vs. ATGs was that they were so thin skinned that almost anything could penetrate their armor, and that was likely the thinking behind the report from Tunisia. Be aware though that the M10 had some of the same problem, though not so severe.

Michael

[SteveP]

Originally posted by Michael Emrys:

I think the big problem of the M3 vs. ATGs was that they were so thin skinned that almost anything could penetrate their armor, and that was likely the thinking behind the report from Tunisia. Be aware though that the M10 had some of the same problem, though not so severe.

Michael [/QB]

Maybe I'm still not making myself clear yet. It's exactly because the officer didn't say this -- "that they were so thin skinned that almost anything could penetrate their armor" -- but rather focused on the flat trajectory issue. That is what puzzled me. Since the quote I saw was taken out of some larger context, I don't want to draw unreasonable conclusions. The officer may have been saying that the TDs were poor on the attack because they were too thin-skinned and had a flat trajectory (and maybe other factors as well). Still, why even bring up the flat trajectory in the first place? The implication is that if the TDs could employ plunging fire, this would provide a significant offset to the thin skin. But why, or how, would this offset be utilized?

[Michael Emrys]

Originally posted by SteveP:

Maybe I'm still not making myself clear yet. It's exactly because the officer didn't say this -- "that they were so thin skinned that almost anything could penetrate their armor" -- but rather focused on the flat trajectory issue. That is what puzzled me. Since the quote I saw was taken out of some larger context, I don't want to draw unreasonable conclusions. The officer may have been saying that the TDs were poor on the attack because they were too thin-skinned and had a flat trajectory (and maybe other factors as well). Still, why even bring up the flat trajectory in the first place? The implication is that if the TDs could employ plunging fire, this would provide a significant offset to the thin skin. But why, or how, would this offset be utilized?

Maybe I'm missing something. Taken at its face, I interpret the officer's statement to mean something like, "Because the gun of the M3 GMC has such a flat trajectory, it is forced to engage ATGs only by direct fire, which makes it too vulnerable to return fire." What that suggests to me is that they were simply not employing them in a manner of which they were capable. Since doing so would have required spotters with comms back to the battery, etc., as well as having trained in the use of indirect fire control, and since those do not seem to have been part of TD organization and doctrine at that time, I guess they simply were not able to do it in Tunisia. TDs as well as tanks did do a fair amount of spotter-controlled ID fire later in the war though, so maybe somebody figured this one out.

Michael

[David I]

I think the good officer was commenting on something any CM player would learn - ie. it is better to take out an AT gun with mortar fire than direct fire.

There are a number of threads that deal with US doctrine concerning HT AT guns and how rapidly that idea fell appart in the field.

You should not tackle AT guns with thin skinned vehicles unless you want to play a PBEM game with me, and I have the AT guns.

DavidI

[SteveP]

Originally posted by Michael Emrys:

Maybe I'm missing something. Michael [/QB]

No, I think you've actually answered my initial question, Michael. It is clear that doctrine, at least at the time of the Tunisian campaign, was to use TDs in a direct fire mode, at least when on attack. The US did not at first understand the German's use of AT gun screens to protect tank forces. However, even after seeing this occur many times, the US still didn't try to switch to indirect fire mode, at least then. Your explanation is the most likely one -- it wasn't because of a limitation in the TD design, but because it took a lot of time and training to change doctrine to use indirect fire. What I didn't know for sure was that there was eventually a change in doctrine to use more indirect fire from AFVs.

[Michael Emrys]

Originally posted by SteveP:

The US did not at first understand the German's use of AT gun screens to protect tank forces.

I guess they should have paid more attention to British reports on the fighting in NA then, because Rommel had employed that tactic for a year and a half. I suspect Feller's reports might have mentioned it as well, as they were pretty encyclopedic from what I've read. (In case you don't recognize the name, he was the military attaché at the US embassy in Cairo, made notorious because he communicated his reports in diplomatic code, which the Italians were reading.)

Michael

[SteveP]

Originally posted by Michael Emrys:

</font><blockquote>quote:</font><hr />Originally posted by SteveP:

The US did not at first understand the German's use of AT gun screens to protect tank forces.

I guess they should have paid more attention to British reports on the fighting in NA then, because Rommel had employed that tactic for a year and a half. I suspect Feller's reports might have mentioned it as well, as they were pretty encyclopedic from what I've read. (In case you don't recognize the name, he was the military attaché at the US embassy in Cairo, made notorious because he communicated his reports in diplomatic code, which the Italians were reading.)

Michael </font>

[SteveP]

Originally posted by Michael Emrys:

</font><blockquote>quote:</font><hr />Originally posted by SteveP:

The US did not at first understand the German's use of AT gun screens to protect tank forces.

I guess they should have paid more attention to British reports on the fighting in NA then, because Rommel had employed that tactic for a year and a half. I suspect Feller's reports might have mentioned it as well, as they were pretty encyclopedic from what I've read. (In case you don't recognize the name, he was the military attaché at the US embassy in Cairo, made notorious because he communicated his reports in diplomatic code, which the Italians were reading.)

Michael </font>

[Michael Emrys]

Originally posted by SteveP:

It just goes to show that not only is there a lot of friction in war, but also a lot of inertia.

As well as a lot of NIH, as illustrated in this case.

Michael