M10 vs. M4 - why have both a TD and a tank?

[JamesValentine]

MOD EDIT:

I've split this topic to clear up the more practical posts from the sillyness (which is still okay, mind, just in a different thread now).

The OP asked about the purpose and rationale behind having both the M4 Sherman tank and M10 tank destroyer when they were broadly similar in armament and resource requirements.

[Abbner Home]

More knowledgeable people will surely pipe up, but...

The US Army at the time had a specific doctrine for what they called Tank Destroyers and those units were not intended to be tanks with a hot AT gun. They were intended to be dedicated anti-tank and thus would not need such frippery as "adequate front armor" or a "closed turret". They were meant for shoot and scoot at medium - long range and were teamed with recon jeeps and armored cars to help located enemy tanks to then destroy.  So the M-10 was the first TD designed to meet that doctrine and thus its existence.

[jamesmanto]

The open turret would make spotting and target acquisition easier.

[Ultravanillasmurf]

I suspect that the key is the difference in weight between the M2/3/6 75mm gun and the 3 inch M7 gun (plus the weight of the ammunition).

Does the quoted weights include the  M10's counterweight? Field expedients weighed up to three tonnes.

[Abbner Home]

I don't think any one is saying that what the Army did was brilliant or wise. Just what their reason was at the time for good or ill.

[Arrigo]

Abbner is broadly right.

The M10 and the follow on M18 and M36 were created to fill the requirement for a full tracked turreted tank destroyer. It was a reaction to the German blitzkrieg as seen in France. The underlining idea was that tanks would have been used for exploitation, and not to get bogged head on against German panzer units. Massed TD groups would have dealt with the panzers. To get these masses of TD they had to be a bit cheaper than full tanks, plus because they were supposed to be faster thank tanks and able to quickly acquire target, the open topped turret and less armour made sense.  The bolts were for add on armour to keep the pace with tank developments.

On paper it made sense in 1940-41, by 1943 when the masses of German panzers are nowhere to be seen... a bit less. But the TDs were McNair (chief, Army Ground Forces) pets so they still soldiered on. There is still an ongoing debate if they were just useless or performed a real service. Certainly they were cheaper, and in some case allowed larger guns to be deployed faster than in tanks. Also the M10 was a derivative of the M3, so it did not really hamper M4 production.

[Cubs]

British tank development shows how easily these cul-de-sacs can be made with (initially) good intentions, which are then carried on through short-term need over longer-term wisdom (perhaps a little harsh, hindsight makes a genius of us all), changing requirements on the battlefield and, most frustrating of all, contractural arm-locks, industrial inflexibility or personal pet projects. 

[SpaceCudet]

It wasn't just that the M10 would be the quickest way to get a better gun into the field, tank destroyers were a different branch of the army with their own requirements. It just happened that these turned out to be pretty similar to a tank's requirements.

Originally, (until someone was impressed by the performance of AT guns in Tunisia) the US were not going to have towed AT guns larger than the 37mm. The bigger guns were considered too difficult to manhandle into position especially as the plan was to being attacking pretty much all of the time. So, it was always the plan to have self propelled AT guns.

   

[Ultravanillasmurf]

Also the M10 was a derivative of the M3, so it did not really hamper M4 production.

I know it is only one source (and YMMV) but Zaloga in NVG57 page 6 states that the original T35 was based on an M4A2, and (page that the Army was so desperate for tank destroyers that they had a higher priority than M4 tanks. There was concern that M4A2 chassis production would not be adequate so the M4A3 chassis was used to build the M10A1.

It might be that the M10 assembly line might have replaced M3 production (but that is speculation on my part).

[Arrigo]

I know it is only one source (and YMMV) but Zaloga in NVG57 page 6 states that the original T35 was based on an M4A2, and (page that the Army was so desperate for tank destroyers that they had a higher priority than M4 tanks. There was concern that M4A2 chassis production would not be adequate so the M4A3 chassis was used to build the M10A1.

It might be that the M10 assembly line might have replaced M3 production (but that is speculation on my part).

Do you know I have Steve's visit card?  There is also a group picture in front of the main building at the RMAS with us standing together! 

There are basically two sources on technical details of US AFV of WW2, Hunnicutt  and Zaloga; both agrees so it is not one source. Zaloga mentions the connection from the  M4A2 not only in the Osprey, but also in Armored Thunderbolt (that he claims, with sound judgment, to be his best book).  I think my comment was confusing because it looked like the M10 was built from M3.  To clarify, it did not replace M4A2 or M4A3 production at all. It was desgined with commonality with the M4A2 (M10) and A3(M10A1) and that made sense to reduce different parts floating in supply depots. The concept itself started as modification off the M3 (the awfully looking M9!), but then it was constantly redesigned to meet changes in requirements and different preferences.  Assembly started at Fisher, where M4A2 were also produced, probably to save on time.

It is also worth to note that while the US Army did not use the M4A2 (Marines and allies did), it did use the twin engined diesel M10. the A1 were either retained in the US for training or, later on, converted into M36.  So basically M10 while sharing a lot of commonalities with both the M3 and M4 (that, from an automotive point of view, were indeed similar until the A3E8), ended up having a production path of its own, based on a limited standard Sherman hull.

[Ultravanillasmurf]

Do you know I have Steve's visit card?  There is also a group picture in front of the main building at the RMAS with us standing together! 

What with that and http://leadadventureforum.com/index.php?topic=114242.msg1429603#msg1429603 it must be like one of Richard Castle's poker nights round at your place. ^__^

So to be clear, your comment

Also the M10 was a derivative of the M3, so it did not really hamper M4 production.

which I agree was unclear, does not represent my (and it appears your) interpretation of Zaloga's views on the development path of the M10 (in my case taken from the NVG57).

Cool.

Oh, I apologise for strange emoticons/emojis appearing in my text, the strange smiley is eight followed by close bracket. It is supposed to be the page reference for the quote but the forum renders it as an emoticon/emoji

The single source reference

I know it is only one source

related to my single source being the Zaloga New Vanguard title.

[Arrigo]

but because Zaloga NVG matched Hunnicutt (and the official sources too) it makes more than a single one 

Oh well people I met around... Heinz Frieser (Blitzkrieg Legend) sitting in front of me in a train; Having a lunch with Richard B. Frank (with me: that Richard B. Frank?  Heim; Do you have read some of my books?), chatting with a Royal Navy Admiral withour realizing he was the husband pf Princess Anne...  having Anthony Beevor's son as a student (in a war studies module), talking with Sir Robert Thompson's daughter (she was doing a PhD at the same time as me),  being introduced to Adrian Goldsworthy ('He  is Adrian'), discussinf the fine art of unguoing torpedo aiming with Paul Kennedy ('oh  so in the end it was just point and hope') well, I had my moments .


On the perverse side: one me and my supervisor (at the time professor Saki R. Dockrill) complaining a lot about 'Eating soup with a knife' and John Nagl, then leaving her office to go downstairs to get some stuff in the department office and then going to grab some food at the canteen and seeing him in the corridor... waiting he was out of sight and chuckling...    of... having an argument with General Petraeus' mistress, without even knowing who she was...


Back to tanks...

[Ultravanillasmurf]

but because Zaloga NVG matched Hunnicutt (and the official sources too) it makes more than a single one 

I do not doubt that, however I had only the Osprey book, so it was my single source which contradicted my understanding of your statement about the M10 being based on the M3.

I did see the Queen Mother drive by while I sat on top of a World War One tank at Bovington forty years ago ^___^.

[Ultravanillasmurf]

Back to Mr Valentines's original question.

From Zaloga NVG57, the design originated as part of the underwear changing moment that was the Blitzkrieg.

The US Army concluded that they needed something and a whole bunch of designs was the result. Most of them made TOG look like cool kit (The M5 3 Inch GMC is described as "clap-trap" - see page 4).

Complaints about the designs led to (US) Ordnance recommending the design of a Tank Destroyer using the 3 inch gun from the M6 heavy tank fitted in a partial (frontal armour) turret on an M4A2. The approved T35 had an all round turret.

Experience in the Philippines December 1941 - January 1942 showed existing designs with vertical plates were vulnerable. This led to the T35E1 with the distinctive sloped armour.

The pilots were too heavy, so armour was reduced from one inch to 3/4 inch plate on the sides.

The final version was type standard as the M10 GMC. As there were concerns about M4A2 production not meeting requirements, a version using the M4A3 chassis was designed as the M10A1.

If you want to know more, I suggest Osprey's NVG57. It tells you all about the bizarre politics of the US Army of the time.

[custosarmorum]

For a thorough discussion of the U.S. development of Tank Destroyers, their doctrine, and employment, I would recommend Christopher Gabel's monograph on the subject, which is conveniently available online:

https://www.armyupress.army.mil/Portals/7/combat-studies-institute/csi-books/gabel2.pdf