US Armor

The US Tank Destroyers evolved through the war and by the the Spring of 1945 their 90mm anti-tank gun was probably the best on the field, after modifications and experience. Starting with the M10 and moving through the M18 and M36, when were they first deployed, how were the guns in action against enemy armor, and how were they improved along the way?

 

First principles, maybe?

T24 perhaps the first US concept of a 'Tank destroyer'? Not having really refreshed the memory on other than medium armour, and assuming other halftrack expediencies might not fit the bill.
It was certainly the direct result of McNair's first push on TD/SPATG doctrine.

From that Hunnicutt man (again) :
M3 basis.
Work begins from October '41.
3 inch mount.
Cancelled April '42, but work on broadly the same vehicle as 'T40' continued alongside and briefly (very briefly) was designated as the substitute standard M9.
M3 based TD work ditched by August '42 as the M10 with it's fancy rotation turret came to fruition.

GMC T24:


GMC T40:

 

Did those ever see service?

I was reading that during the battle of Tunisia the Americans only had half-track M3s, and no M10?

 

No, no service for the M3-based gun carriers, just the full-track progenitors of the Medium breed.

I think M10 did just get in towards the end of the Tunisian campaign, but would have to check.
Decent enough gun for that period, but despite it's ubiquity for a while the M10's big problem was that it really didn't fit the requirements laid out for TDs in new US doctrine. Nothing was perfect though - any old port in a storm - and it eventually found it's role once TD doctrine fell away a bit.
M18 always strikes me as what McNair really wanted, and when you watch one blatting around at full speed you start to at least get a glimpse of what they intended with the concept.

 

So before the M10, they used the half-truck with the cannon?

 

Yes, and M6s, but as you're doubtless aware that particular style of GMC wasn't really fulfilling anyone's ideal of aggressive US TD doctrine; despite their mixed successes... and failures.
Crewed in the finest spirit and with immense bravery in Tunisia, but lacking what was really required as machines that might prove the concept.

 

I found the following for 1st combat with the M10:

899th TD Bn - March 24, 1943, East of El Guettar, Tunisia
776th " - March 27, 1943, at Maknassy, Tunisia
601st, 701st, 805th, 813th and 894th used the M6/M3's although by March, 43, there were enough M3's in theater that the M6 was phased out.

 

I just did some extensive research on TDs for my current book. The M10 (British gave it the name Wolverine, and the US never used it) was based off the M4 Sherman chassis and used the 3 inch (76 mm) M7 Gun. They used the M4 chassis due to it being produced in numbers and they thought it could be fixed/repaired quicker in the field. The problem was that they did not have a powerful engine and were slow. Later models had the 90 mm gun which made it a very effective TD.

The M10 was the first tracked TD that could traverse 360 degrees.

The M18 Hellcat was also developed using the M4 chassis, but from lessons learned with the M10, came with the 90 mm gun and had stronger/better engines. It was much faster than the M10. The M18 could keep up with the armor it was designed to support.

 

There is some debate as to whether the 'Wolverine' name was ever actually used in wartime for M10.
Current thought is that it's very much a postwar addition to the lexicon, as nobody can find any contemporary references to it as such in British or Commonwealth usage.
The blessed David Fletcher seems to have led the charge on this thought, and it appears, as ever, that he may well be right.

 

I thought the M18 used a different frame. Or maybe I'm thinking of the Chrysler engine? I remember something different about the M18 Hellcat. So M10s weren't brought it until towards the end of Tunisia? I just watched this documentary that showed the only tanks and TDs used by the US were the Shermans, Grants, and M3 half-tracks in NA. That must have been before March 1943.

 

Some confusions here. This is from Appendix I to my manuscript of For Purpose of Service Test.


Tank Destroyer and Antitank Artillery
[SIZE=12pt]M6 GMC[/SIZE][SIZE=12pt] (T21, Standardized February 1942, re-designated Limited Standard September 1943 and declared obsolete January 1945) was a simple conversion consisting of mounting a M3 37mm antitank gun onto the bed of a Dodge ¾-ton 4 x 4 weapons carrier. It was never intended to serve in combat, but was simply an interim training vehicle for the Tank Destroyer Force and as a substitute for purpose-built armored cars in mechanized cavalry units. Nonetheless, some saw service in Tunisia with American forces following the Torch landing, but they proved to be hopelessly inadequate as a service weapon. Production began in May 1942 and continued through May 1943, for a total of 4,117 built.[/SIZE]

[SIZE=12pt]T48 GMC[/SIZE][SIZE=12pt] (not standardized) was another simple conversion consisting of the M1 57mm antitank gun mounted on a M3 halftrack. Production began in December 1942 and continued to May 1943, for a total of 962 built. It was never used by U.S. forces, but was Lend-Leased to Great Britain (30) and the U.S.S.R. (650).[/SIZE]

[SIZE=12pt] On 2 May 1942, a meeting between General Bruce, president of the TD Board, and representatives of Ordnance and of the Requirements Division of the War Department was held at Aberdeen. During the conference they viewed tests of the new 3-inch T35 GMC developed as a joint effort by General Motors and Ford. Bruce refused to approve standardization of the vehicle, deeming it another expedient vehicle that was too slow and heavy for Tank Destroyer requirements. Nevertheless, Bruce was overruled and the vehicle was standardized as the M10 (GMC design with twin diesel engines) and the M10A1 (Ford design with their V-8 air-cooled gasoline-powered tank engine), which were then issued to the Tank Destroyer battalions.[1][/SIZE]

[SIZE=12pt]M10 GMC[/SIZE][SIZE=12pt] (T35E1, Standardized October 1942) was the first purpose-built Tank Destroyer. It mounted a modified 3-inch antiaircraft gun known as the M7 Tank Gun in an open-topped turret on a lightened M4A2 Medium Tank chassis. Later, the standard M4A3 Medium Tank chassis was utilized with the same turret resulting in the M10A1. Production began in September 1942 (the first saw service in Tunisia in February 1943) and continued to December 1943, for a total of 6,706 built. Of those, 4,993 were M10 built by Grand Blanc (September 1942-December 1943), 1,038 were M10A1 built by Ford (October 1942-September 1943) and 675 were M10A1 built by Grand Blanc (September-November 1943). Later, from April 1944 through August 1945 a total of 237 M10 and 1,859 M10A1 were converted to M36 (see below). Lend-Lease shipments were 1,648 to Britain, 443 to French forces and 52 to the U.S.S.R.[/SIZE]

[SIZE=12pt] Meanwhile, work continued on the vehicle most desired by General Bruce, the 57mm T49 GMC. However, Bruce desired a weapon heavier than the 57mm and on 2 July 1942 requested it be replaced with the 75mm M3 Tank Gun. At the same time, work had continued by General Motors on a 3-inch GMC with a torsion bar suspension. On 3 September 1942, Bruce was viewing tests of that vehicle at Aberdeen when General Barnes mentioned to him that a new 76mm gun had been developed.[/SIZE]

[SIZE=12pt] The General Motors vehicle was designated the 75mm T67 GMC on 19 November 1942. Representatives of the Tank destroyer Board, Ordnance, and General Motors met in Detroit on 22-23 December 1942 and decided to change the armament to the new 76mm gun. The new concept fit Bruce’s concept of the “perfect” Tank Destroyer vehicle and on 31 December 1942 he ordered its adoption by the Tank Destroyer Board. On 7 January 1943, the T67 project was closed and then reopened by the Ordnance Department as the 76mm T70 GMC.[2][/SIZE]

[SIZE=12pt]M18 GMC[/SIZE][SIZE=12pt] (T70, Standardized February 1944) was the first Tank Destroyer built as such from the initial design stages and incorporated the features desired most by the Tank Destroyer Force, speed, maneuverability, quietness, and light weight, combined with the M1 76mm Tank Gun. However, it also sacrificed all but the lightest of armored protection and like the M10 and M36 utilized an open-topped turret. Production by Buick began in July 1943 and continued through October 1944, for a total of 2,507 built. Only seven were shipped as Lend-Lease, two to Britain and five to the U.S.S.R.[/SIZE]

[SIZE=12pt]M36 GMC[/SIZE][SIZE=12pt] (T71E1, Standardized June 1944) was an Ordnance development designed to mount the more powerful M3 90mm Tank Gun onto the same chassis as the M10 (M36B2) and M10A1 (M36) Gun Motor Carriage. Initial production of the M36 began at Grand Blanc (300, April-July 1944), followed by Massey-Harris (500, June-December 1944), American Locomotive (413, October December 1944), and Montreal Locomotive (85, May-June 1945). Total production was 1,298 M36, with an additional 561 converted from M10A1, May-August 1945. M36B1 production converted from M4A3 Medium Tanks was 187 at Grand Blanc (October-December 1944) and 237 M36B2 were built by American Locomotive (May-August 1945), but none of the M36B2 saw service in Europe. Total production of all types was 2,283.[/SIZE]


[SIZE=10pt][1][/SIZE] Lt. Col. Emory A. Dunham, The Tank Destroyer History, Army Ground Forces Study No. 29 (Washington, D.C.: Historical Section – Army Ground Forces, 1946), p. 59-61.


[SIZE=10pt][2][/SIZE] Dunham, ibid.

 

Between the three main Tank Destroyers based on tank design, the US only made over 11,000. That's not that many compared to number of Sherman tanks made (over 49,000). Well I guess it is, since Germany made a total of 25,000 tanks of ALL types. We made almost half of that in just TDs.

 

Correction: Germany made just over 49,000 tanks and self-propelled guns of all types. The US made just over 49,000 Sherman tanks alone. Then add the 11,000 Tank Destroyers, M3 Grant (obsolete but still used), M24 Chaffee and M26 Pershing used towards the end of the war.

To that add the British tanks and self-propelled guns. Germany was definitely out-numbered.

 

I forgot the older light tanks. I just saw a statistic, the US produced over 88,000 tanks and self-propelled (TD) guns for WWII. That plus 300,000 aircraft is incredible.

 

87,178 tanks actually...more or less. From July 1 1940 to 1 September 1945, 28,885 light tanks, 55,876 medium tanks, and 2,417 heavy tanks. GMC, HMC, and specialized vehicles were counted separately. 49,422 Medium Tanks M4 were built.

 

Does that count M18, M10, and M36 since they were tank chassis?

 

Both the M10 and M18 used the Sherman chassis. The M10 had a low power engine until it was upgraded. At about the same time the gun was upgraded to the 90 mm.

The M18 came out with the high power engine and 90 mm gun

 

I added the bold.

The M18 (T70) was a 'ground up' design, it did not use the Sherman chassis. It was armed with the 76mm main gun as stated above. The only US TD to use the 90mm gun was the M36.

 

Indeed. Neither the 57mm T49 or 75mm T67 GMC used "Sherman chassis"...and nowhere did I say they did. The GM-developed chassis was radically different from the "Ordnance-standard" chassis, although I'm sure Barnes was happy they used "his" torsion bar suspension.

 

No, they did not. The M10, as I already said, used a modified Medium Tank M4A2 chassis with the twin GM diesels. It was never "upgraded", although some M36 with 90mm gun were built on the standard M4A3 chassis with the Ford GAA V8 gasoline engine. The M18 GMC was a completely different animal designed by GM. It had a very light chassis, not a high power engine - the engine was essentially the same as in the M4 and M4A1. It never had a 90mm gun, although attempts were made to fit it.