Why did the US Army focused on using "open top" on tank destroyers?

[tankerwanabe]

Why did the US Army focused on using "open top" on tank destroyers and mobile artillery during WW2? M10,M36, Hellcat etc.

 

Did abandoning its use an acknowledgement that it was a failed design?

[Guest JamesG123]

It was hardly a "failed design".

 

US TDs were not tanks, more like self-propelled anti-tank guns. They may have look like tanks, but their armor was very thin. The TD as well as the other SPG were intentionally built with open tops to save weight, improve their ability service the guns, and in the TD's case increase the visibility of the crew.

 

US SPG only became fully enclosed after the war in order to operate in NBC environments and as further protection against shell fragments.

[Old Tanker]

Save money...cheap....cheap....save money.

 

The TD's were designed for one mission, defeat hordes of Panzers from defilate ambush positions. Direct fire AFV vs. AFV engagements.

 

Not urban warfare , not jungle warfare , not infantry support. Since all combat was invisioned in direct fire anti-AFV mode no top needed. Also less weight resulted in better speed and observation. By the end of the war some units were installing theater made tops as tree bursts arty fire severly limited use of TD's under tree coverage forcing them into open terrain and extreme exposure in city built up areas.

[Colin]

Canadian M10's were withdrawn from service in Korea partly because it was felt the open tops were at a big risk of having a grenade tossed into them. The open top gave them excellent situational awareness which was useful for hunting tanks.

[Mk 1]

Why did the US Army focused on using "open top" on tank destroyers and mobile artillery during WW2? M10,M36, Hellcat etc.

 

Your question contains the seeds of its own answer.

 

As others have pointed out, and as you have indicated in the question, tank destroyers were seen as a form of mobile artillery.

 

Perhaps from our point looking backwards, it is quite obvious that mobile guns should be fully enclosed in armor. But it was not at all clear at that time.

 

If you look at German panzerjaeger designs you will also see many open-topped, and even open-backed vehicles. Look also at the Soviet SU-76, or the many other SPG platforms that never saw such wide-spread use, like the various SU-45 incarnations.

 

The variety of designs that were created for tank destroyers shows a struggle to come to an understanding of what the vehicle needed to be. Tank destroyers were classified as GMCs - for Gun, Motor Carriage. The M6 GMC "Fargo" was nothing more than a 37mm AT gun on a truck bed, with an expanded splinter-shield. Very similar in concept and implementation to the French Laffly AT SPG that was produced at the very end of the May/June 1940 campaign. The M8 amored car "Greyhound" was first envisioned by the tank destroyer board as an improvement to the "Fargo" - a fast vehicle armed with an AT gun, with protection against shell spinters and small-arms, and in this case also with some reasonable measure of cross-country performance. The M4 GMC, with a 75mm gun on a half-track, was also in this line, but with even more gunpower and marginally more cross-country performance.

 

Roughly concurrent with those designs there were several design proposals and prototypes for specialist AT tracked vehicles, including very light tracked platforms with guns (on the Cletrac and M3 Stuart chassis) and medium tracked platforms (on the M3 "Lee" and M4 "Sherman" chassis). Some used fixed superstructures (much like the later M7 HMC "Priest", but with a 3-inch AT gun), some used only a gun-shield, and some used turrets with armor only over the frontal arc. In time, the Tank Destroyer board settled on all-around armor, but never went for overhead armor.

 

As described by others, TD crews were expected to have the edge in head-to-head fighting with tanks, in that they would have better situational awareness and could serve their guns faster. Have you ever heard a tank moving by? They can be heard from several KM away. But not if you are IN a tank at the time. So you kept your head out. On a TD, everyone in the turret crew had their head out, all the time.

 

Did abandoning its use an acknowledgement that it was a failed design?

If I might paraphrase Harry Yiede (who we may hope to see in this thread shortly), if we look at their combat record, the US Army TDs of WW2 were probably the most successful failure in military history.

 

But yes, in the end the designs, and the doctrine behind them, were considered failures. Too specialized for the investment needed to make them effective in their intended role. They had to be more mobile than their opponants, and have high AT firepower. They were intended to be held as higher-echelon reserves, ready to move forward at any moment to outmaneuver and outshoot enemy tank breakthroughs. To be effective in their envisioned role, they had to be available in substantial concentrations. But the US Army was almost relentlessly on the attack, and throughout two and a half years of combat operations there were only really two occasions of substantial panzer breakthroughs. You simply could not expect commanders to keep a large quantity of AFVs sitting around idle while troopers were dying on the front lines every day, and every operation that you suported with tanks -- ANY tanks -- achieved more, at a lower cost in lives.

 

So, in the end, tank destroyer battalions wound up serving like better-trained, under-armored independant tank battalions, or heavily-gunned cavalry squadrons. In those roles they served well, achieved excellent results, but surely could have used more tank-like features such as co-ax MGs and overhead armor.

 

-Mark 1

[Akhe100]

First off it's very simple why. First off they were working with the already flawed tank-destroyer doctrine which counted on the fact that our tanks wouldn't have to engage enemy tanks, a laughably unrealistic assumption. Also let me say one thing without a doubt. When has something being a bad idea (which it was as it left them open to even the slightest of shell bursts, well aimed grenade tosses and not to mention the elements) stopped something from being used? Want examples?

1. Panzer VIII maus

2. V-2 Rocket

3. The Tiger II

4. The Cruiser+Infantry Tank doctrine

5. The use of stuka without air-superiority

6. The use of the ME-262 as a bomber.

Dude, the list goes on, just because something is stupid, doesn't mean it's not going to be made.

[KingSargent]

First off it's very simple why. First off they were working with the already flawed tank-destroyer doctrine which counted on the fact that our tanks wouldn't have to engage enemy tanks, a laughably unrealistic assumption.

A misconception. The American tank had a role in engaging enemy tanks, but that was not its PRIMARY role - infantry support and exploitation were. The Medium's gun was optimized for infantry support. Even the US Light Tanks with the 37mm gun carried HE and cannister ammo, which was about the best you could get for infantry support from a small caliber, as opposed to the British 'AP Shot only' 2pdr ammo.

[Akhe100]

They were made with the point that tanks weren't supposed to engage other tanks, as I said, a laughable proposition,and were overall equipped fairly poorly to do so. Even it's upgraded 76mm gun could only penetrate 89mm of armor, which can't even kill a panther from the front, much less a tiger.

[Meyer]

5. The use of stuka without air-superiority

 

Yeah, I'm sure that not using the JU87 in the 1940 campaign, Barbarossa, Mediterranean, etc, would be really smart.

[Akhe100]

Use of it in the bombing raids on britain and some of it's use of the eastern front were essentially turkey shoots.

[Meyer]

Use of it in the bombing raids on britain and some of it's use of the eastern front were essentially turkey shoots.

 

No, they were not. And even if that was the case (which wasn't), still doesn't make it stupid the use of the Stukas.

[Akhe100]

Do you have any idea how many stukas were downed by the RAF during the Battle of Britain, I believe the number was in the hundreds. It was a great close air support weapon but they tried to use it as a medium range strategic bomber, which it was not. It was put to great use when they had air superiority and in places like the medditeranian where the allies had supply problems. But they suffered extremely heavy losses in the late war vs the russians and during the battle of britain.

[Meyer]

Not hundreds, 59 Ju87's were lost in the period july 2-august 18. And of course the Lw never tried to use it as a "medium range strategic bomber"...

Edited August 30, 2007 by Meyer

[KingSargent]

They were made with the point that tanks weren't supposed to engage other tanks,

WRONG!!! There was NOTHING in US doctrine that said that US tanks were not supposed to engage enemy tanks. They were not supposed to go HUNTING enemy tanks, but nothing said they were not supposed to shoot them if they appeared.

 

as I said, a laughable proposition,

Not at all, since your imaginary proposition is untrue.

 

and were overall equipped fairly poorly to do so.

Really? Who had the best AT gun in tanks in the Western Allies from 1942-44?

 

Even it's upgraded 76mm gun could only penetrate 89mm of armor, which can't even kill a panther from the front, much less a tiger.

Panthers were not seen in the West until long after the 76mm was in production, so it would be hard to design the gun to counter it, would it not? As for the Tiger, the US and USSR both considered it a minimal threat since the Germans would not be able to make enough of them to make much difference - as proved to be the case.

[Chris Werb]

Really? Who had the best AT gun in tanks in the Western Allies from 1942-44?[/b]

 

The UK? (6 and 17 pounder)

[KingSargent]

The UK? (6 and 17 pounder)

!7pdr was not a tank gun until into 1944. There was little practical difference between the 75mm M3 and the 6pdr in actual AT performance in combat before APDS. There were also lots more 75mm gun tanks in combat than 6pdr tanks and most of the 6pdr tanks had the gun and two men shoehorned into a 2pdr turret.

[Olddog84]

I have always seen the US Tank Destroyers as better versions of the German Marder concept. It was pretty standard in WWII to take an anti-tank gun and give it mobility by putting it on some type of wheeled, later tracked, platform. Look at the profusion of lashed-up designs the Germans came up with using all types of obsolete chassis in order to give many units some type of mobile anti-tank ability. The only difference is the US types were purpose-made, and having all round turrets, better designs.

 

I have always found the assertion that the US should have listened to their "wiser and more experienced" British comrades and adopted the 17 pounder prior to Normandy laughable. What exactly had the British done in the realm of tank design that would have made anyone think they knew anything about proper tank design at the time? Don't get me wrong, I love the British and I am a confirmed Anglophile, but their tank design and production policies were ludicrous. They failed to produce an indigenous design for a medium (or "heavy cruiser") capable of even mounting the 75mm gun until the Cavalier / Cromwell, and even then it's tactial and strategic value only equaled the sherman, and had no room for stretch potential in any case (unless you count the Comet as a Cromwell stretch). This fascination with the 6 pounder as a medium tank armament in 1944 is ludicrous. The majority (by far) of rounds fired were high explosive, not ap, and the 75mm was a much better he weapon.

 

The best that you can say is that the British did realize the need for some highly effective ap capability and adapted the weapon to the best medium tank design in service with the western allies at the time, the sherman (an American design). It is also right to say that they also got it right and did not arm all of the shermans with the 17 pounder (not that it was even possible for them to produce enough to do so in time for D-day) but kept most of the tanks armed with a weapon firing a superior he round for its caliber.

 

I

[Akhe100]

1. Sorry, sargent, you're the one who one who is wrong, the allied doctrine was that the purpose of tanks was not to fight other tanks, but to be infantry support weapons and as such they were not made well to fight tanks. This is a laughable proposition as this assumes that tanks will not often have to fight tanks.

2. While I agree that the british may not have had a good record when it came to tank building, the 17 pounder was arguably superior to anything that either side had at time, exceeding even the great 88 in armor penetration (while being smaller and lighter).

3. Sergent, frankly, it doesn't MATTER what the best western allied anti-tank gun was because the western front allies were just overall pretty bad at tank combat. It wasn't until the 17 pounder that we got a really good anti-tank gun (it was amazing when used on the sherman firefly) but it wasn't used that much on tanks. The eastern front allies had them beat hands down with their 100mm anti tank gun and their 85mm tank gun (which was put on tanks as early as '43)

[Marek Tucan]

1. Sorry, sargent, you're the one who one who is wrong, the allied doctrine was that the purpose of tanks was not to fight other tanks, but to be infantry support weapons and as such they were not made well to fight tanks. This is a laughable proposition as this assumes that tanks will not often have to fight tanks.

The doctrine AFAIK stated that TD's are primary antitank asset while tanks were primarily to bolster up infantry with HE, but still it required tanks to carry AP shells (that had enough power for most German armor assets sent to front). AFAIK the theory was for Sherman ca. 50/50 split between HE and AP (someone some time ago posted here excerpts from field manuals regarding HE/AP loads of ammo), hardly a choice for vehicle that is not meant to fight tanks.

 

2. While I agree that the british may not have had a good record when it came to tank building, the 17 pounder was arguably superior to anything that either side had at time, exceeding even the great 88 in armor penetration (while being smaller and lighter).

British had only limited cap in production of 17pdr, priority went to AT-Guns and anyway 17pdr mounted in Sherman was rather awkward in terms of RoF. Besides, US were producing 76mm, which wasn't as great but was lighter and smaller, easier to load.

 

3. Sergent, frankly, it doesn't MATTER what the best western allied anti-tank gun was because the western front allies were just overall pretty bad at tank combat. It wasn't until the 17 pounder that we got a really good anti-tank gun (it was amazing when used on the sherman firefly) but it wasn't used that much on tanks. The eastern front allies had them beat hands down with their 100mm anti tank gun and their 85mm tank gun (which was put on tanks as early as '43)

 

Soviets got 100mm ATG IIRC later than US got comparable 90mm (both on mobile and towed platform) and in summer 1943, 85mm was mounted on few heavy tanks, while the US got 3in with comparable performance mounted on a number of M10 Tank Destroyers. T-34/85 also got produced in roughly the same time as 76mm armed shermans and "Western front allies were overall bad in tank combat" - me thinks they were at least equal to Red Army in this aspect.

[Vasiliy Fofanov]

The eastern front allies had them beat hands down with their 100mm anti tank gun and their 85mm tank gun (which was put on tanks as early as '43)

 

85mm gun is roughly equivalent to US 76mm in anti-armor potential.

[Akhe100]

Actually that is wrong, the 76mm gun on the sherman could penetrate 89mm of steel at 1000 meters where the 85mm gun on the T-34/85 could penetrate 102mm of steel at 1000 meters, this is a significant difference.

[R011]

1. Sorry, sargent, you're the one who one who is wrong, the allied doctrine was that the purpose of tanks was not to fight other tanks, but to be infantry support weapons and as such they were not made well to fight tanks. This is a laughable proposition as this assumes that tanks will not often have to fight tanks.

And your source for this is? Incidentally, while this has been said for American doctrine, it certainly wasn't true of British doctrine.

 

2. While I agree that the british may not have had a good record when it came to tank building, the 17 pounder was arguably superior to anything that either side had at time, exceeding even the great 88 in armor penetration (while being smaller and lighter)

.

 

It had a poor HE capability until late 1944, IIRC, as the gun and original HE rounds had too high an MV. Nor was a tank designed specifically to take it until the Centurion, the Challenger and Firefly being expedient lashups with notable limitations. Meanwhile, as far as the US Army knew until mid 1944, the 76 mm was perfectly capable of handling the then known German threat. The next step for the US was the 90 mm.

 

3. Sergent, frankly, it doesn't MATTER what the best western allied anti-tank gun was because the western front allies were just overall pretty bad at tank combat.

 

Somewhat true of the British only until 1943. Not really true of the Americans after North Africa.

 

It wasn't until the 17 pounder that we got a really good anti-tank gun

On the contrary, the Western Allies had excellent AT guns until mid 1944 and even then, the 76 mm and 3 inch were able to handle most German AFV targets with little trouble. Note too that the 90 mm entered combat unit service in September 1944.

 

it wasn't used that much on tanks.

 

Mostly because it was a big gun that needed a big tank. It didn't really fit well on the Sherman and as I said, the first tank properly designed to take it didn't come out until 1945.

 

The eastern front allies had them beat hands down with their 100mm anti tank gun

There were only 185 of them in operational service in January 1945. By comparison, the US had twenty-one M36 battalions with a TOE strength of eighteen guns each. Penetration of the 100 mm gun was 130 mm at 1000 meters with APCBC. The US 90 mm had a penetration of 122 mm at 914 meters (1,000 yards) with APCBC. The 17 pounder seems even better - 130 mm with APCBC, the normally used round, and 192 mm with APDS at 914 meters.

 

and their 85mm tank gun (which was put on tanks as early as '43)

 

In fact, the T-354-85 entered production only a few weeks before the 76 mm armed Sherman. Nor was the 85 mm much better than the US 76 mm with a penetration of 90 mm at 1000 meters with APCR compared to 88 mm at 914 meters with APCBC and 135 mm with APCR (HVAP), though the latter was in very short supply. Of course, the US 90 mm was entering service about the same time and it's closer to the 85 mm in caliber than the 76 mm is.

 

http://www.militaryhistoryonline.com/wwii/usarmy/armor.aspx

 

http://gva.freeweb.hu/

Edited August 30, 2007 by R011

[R011]

Actually that is wrong, the 76mm gun on the sherman could penetrate 89mm of steel at 1000 meters where the 85mm gun on the T-34/85 could penetrate 102mm of steel at 1000 meters, this is a significant difference.

That's at a 30 degree angle target for the US gun and a 0 degree angle for the Soviet gun. The figures I'm using are all 30 degrees.

[Akhe100]

And your source for this is? Incidentally, while this has been said for American doctrine, it certainly wasn't true of British doctrine.

I never said anything about the british doctrine

.

 

It had a poor HE capability until late 1944, IIRC, as the gun and original HE rounds had too high an MV. Nor was a tank designed specifically to take it until the Centurion, the Challenger and Firefly being expedient lashups with notable limitations. Meanwhile, as far as the US Army knew until mid 1944, the 76 mm was perfectly capable of handling the then known German threat. The next step for the US was the 90 mm.

Somewhat true of the British only until 1943. Not really true of the Americans after North Africa.

I dunno about that look at villers bocage for an example of british tank performance in france. And you have to remember that we had 40 something thousand shermans, they had 5,000 or so panthers and 2,000 tigers of both models. Numbers like that tend to make a difference.

 

 

 

On the contrary, the Western Allies had excellent AT guns until mid 1944 and even then, the 76 mm and 3 inch were able to handle most German AFV targets with little trouble. Note too that the 90 mm entered combat unit service in September 1944.

Mostly because it was a big gun that needed a big tank. It didn't really fit well on the Sherman and as I said, the first tank properly designed to take it didn't come out until 1945.

 

While it was somewhat big in the sherman, the performance of the sherman firefly's were good, even being credited with the kill of tank ace michael wittman.

 

There were only 185 of them in operational service in January 1945. By comparison, the US had twenty-one M36 battalions with a TOE strength of eighteen guns each. Penetration of the 100 mm gun was 130 mm at 1000 meters with APCBC. The US 90 mm had a penetration of 122 mm at 914 meters (1,000 yards) with APCBC. The 17 pounder seems even better - 130 mm with APCBC, the normally used round, and 192 mm with APDS at 914 meters.

In fact, the T-354-85 entered production only a few weeks before the 76 mm armed Sherman. Nor was the 85 mm much better than the US 76 mm with a penetration of 90 mm at 1000 meters with APCR compared to 88 mm at 914 meters with APCBC and 135 mm with APCR (HVAP), though the latter was in very short supply. Of course, the US 90 mm was entering service about the same time and it's closer to the 85 mm in caliber than the 76 mm is.

 

First off you just proved that the 100mm was better than the 90mm and I already said that the 17 pounder was an excellent gun . Ok the source I was using didn't give the angles for both tests so I assumed they were both for verticle, so I'm gonna have to take a look at some other books I have to check the angles.

Edited August 30, 2007 by Akhe100

[Marek Tucan]

Actually that is wrong, the 76mm gun on the sherman could penetrate 89mm of steel at 1000 meters where the 85mm gun on the T-34/85 could penetrate 102mm of steel at 1000 meters, this is a significant difference.

 

You are forgetting one "quite important" fact US penetration tests were made at 30°angle.

76mm M1 Gun is rated:

92mm @914 m with M79 AP, that is ca. 106mm @0°

88mm @914 m with M62 APCBC, that is ca. 102mm @0°