Categories
WW2 US Prototypes

Medium Tank T6 – The Birth of the Sherman

USA (1941)
Medium tank – 1 built

On the 2nd of September 1941, a single tank was completed and drove under its own power for the first time at Aberdeen Proving Ground (APG) in Maryland. It was the first of nearly 50,000 and the first U.S. designed tank to employ the now standard concept of a three man turret crew. Only 13 months later it would see its first action in the North African desert in the second battle of El Alamein with the British Army and would remain in frontline service for another 30 years in various forms with a variety of countries. The tank was the T6 and it would become the legendary Medium Tank M4 or as the British named it, the Sherman.

Design Development

On the 31st of August 1940, the United States Army Armored Force submitted detailed characteristics for a medium tank to replace the Medium Tank M3, even though the design of the M3 hadn’t been finalised and was not expected to be in production before the following summer. The M3 was a stop gap design and its shortcomings were already apparent. The most obvious shortcoming of the M3 was the location of the main 75mm gun in a limited traverse hull mounting, so the highest priority was given to designing a suitable fully rotating turret for 75mm main gun. The Armored Force also listed in its requirements a lowering of the overall height of the tank in comparison to the M3 and a provision for anti-aircraft protection.
As the design process of the M3 was fully occupying the design team at Aberdeen, the new tank had to wait until the M3 design was completed. On the 1st of February 1941, the Chief of Ordnance released a directive to proceed immediately with the design of the M3 replacement.
At a conference at APG on the 18th of April 1941, the major features were confirmed for the new design. The basic chassis of the M3 was to be retained including the lower hull, engine, gearbox and final drive, suspension and tracks, most of which had already been carried over from the previous Medium Tank M2. Two main reasons for the M2/M3 carryovers were an ease of transition on the production lines from the M3 to the new tank and because the M2 chassis dimensions were already designed with mass transportation in mind. The original M2 was built to fit a standard gauge railway flatcar. The U.S. was under no illusion that it would be fighting a major war in the continental United States, so priority was given for a mass produced vehicle able to be shipped across oceans with as little alteration to existing transportation infrastructure as possible.
Although the design was based around the continued use of the Wright R975 radial engine, the engine bay was designed with enough space to accept larger engines in the future as they became available.

The new upper hull was to be either cast or welded and was to use as many existing components from the M3 design as possible. The turret ring was increased to 69” (1752.6mm) and the armor thickness was to be a maximum of 3” (76.2mm) on the glacis. The twin fixed .30 caliber machine guns (operated by the driver) were to be retained from the M3 design as well as a new bow mounted .30 caliber machine gun (operated by the co-driver, also known as the bow gunner or BoG) on the right hand side of the glacis.

Two escape hatches were to be placed (one on either side) of the hull sponson plates to allow the crew the ability to bail out of a damaged vehicle on the leeward side of any incoming fire.
The turret was to have a removable plate to allow the fitting of a selection of armament combinations. Five possibilities were considered:
(1) One 75mm (2.95”) gun M2 with a .30” (7.62mm) coaxial machine gun.
(2) Two 37mm (1.45”) guns M6 with a .30” (7.62mm) coaxial machine gun.
(3) One 105mm (4.13”) howitzer with a .30” (7.62mm) coaxial machine gun.
(4) Three .50” (12.7mm) machine guns mounted for high angle anti-aircraft fire.
(5) One British Qf 6pdr (57mm) high velocity gun with a .30” (7.62mm) coaxial machine gun.
Although not listed in available reference material, one other combination was obviously considered at some point as a picture depicts the wooden mock up with a different style turret with a 75mm M3 main gun and a 37mm M6 coaxially mounted. The commander’s cupola from the M3 with its high angle .30 caliber anti-aircraft machine gun was to be retained. It was hoped that this design would allow a single vehicle design to be equipped to meet a number of tactical missions.
The crew was to be reduced to five with a driver and co-driver in the front of the lower hull and three man turret crew in the arrangement that would become the standard for all future U.S. tank designs. The gunner was to be on the right of the gun at the front of the turret with the vehicle commander behind and slightly above him under the cupola. The loader was on the left of the main gun with the .30 caliber coaxial machine gun to his front. The turret crew would share a single roof hatch and the two hull crew would share a single roof hatch on the left side of the hull and a floor escape hatch just behind the co-driver’s seat (these were obviously augmented by the two sponson escape doors).
The T6 full size wooden mockup, to aid speed the lower hull and running gear was reused from the wooden mock up of the M3.
The T6 full size wooden mockup, to aid speed the lower hull and running gear was reused from the wooden mock up of the M3.
In May 1941 the Ordnance Committee recommended a full size wooden mockup and a pilot tank to be built. This was approved in June 1941 and the new design was designated Medium Tank T6. Once the wooden mock up was completed, Aberdeen was instructed to build a pilot model using a cast upper hull. The casting of both hull and turret was to be done by the General Steel Castings Corporation of Granite City, Illinois. At the same time the Rock Island Arsenal was instructed to build a welded hull version but this was delayed because of modifications to the design to reduce the number of plates and the length of the welded joints.

The T6 Pilot

The pilot T6 was completed at Aberdeen on the 2nd of September 1941, and was inspected by representatives of both the Armored Force and the Ordnance Department. The pilot used a donor lower hull, suspension and tracks from an M3 to aid speed to the project.
The T6 pilot on presentation day
The T6 pilot on presentation day, original features that were soon removed include 1) the M3 commander’s cupola 2) side grab handles and 3) the circular armored cover for the antenna base. Picture credit: sherman_minutia
As built, the T6 had side doors but without the vision devices as seen in similar doors on the M3. The bow mounted .30 caliber was linked to a sight rotor in the upper hull casting and both hull crew positions were equipped with direct vision slots with hinged armored covers. The driver also had a periscope mounted in the hatch above his head and his seat was height adjustable allowing him to drive with his head out of the hatch when open, or lower down with the hatch closed using either the periscope of direct vision slot for observation. The twin .30 caliber machine guns were operated by the driver with a limited elevation.
A pistol port with a protectoscope (an armored glass vision port) was located on each side of the turret, and the gunner’s sight rotor was linked in the same way as the bow machine gun. This linkage only moved the top mirror in the periscope which if damaged could be replaced from within the tank by way of a mirror magazine that was integral to the sight.
The gun mount (T48) was designed for the longer barreled M3 75mm (2.95”) gun (L40) but as none were available the shorter M2 75mm (L31) gun was installed. This was breech heavy in this mount and prevented the gyrostabilizer from working correctly. Counterbalance blocks on the muzzle were required to remedy this and were installed shortly after presentation day. The gyrostabilizer was essentially the same as the unit used on the M6 37mm (1.45”) in the M3 Medium Tank.
The T6 was fitted with two radios, one in the front right of the hull, operated by the co-driver (an SCR 506) and one in the turret bustle for use of the commander (an SCR 508). The radio brackets in the turret were also designed to take the British No. 9 radio set.
The co-driver’s position showing twin bow machine guns and the linkage bar to the rotor sight with the SCR506 radio behind.
The co-driver’s position showing twin bow machine guns and the linkage bar to the rotor sight with the SCR506 radio behind.
At a conference on 3rd September, a number of key changes to the T6 were agreed for any further production models, these included;
(1) Removal of the M3 style commander’s cupola to be replaced with a commander’s split hatch that would become standard on the M4.
(2) Removal of the hull sponson doors, as they were considered to be too great a compromise of the armor integrity and also restricted the amount of main gun ammunition that could be stowed in the sponson racks.
(3) A rotating periscope would be retrofitted in the turret roof above the loader’s position.
(4) The rotor mount bow machine gun was to be replaced with a ball mount.
(5) If possible a .50 caliber (12.7mm) anti-aircraft machine gun be installed.
(6) A gun shield should be added to protect the gun mount from splash damage.
The conference confirmed that the T6 would be standardized as the Medium Tank M4.
The M3 style cupola was removed very soon afterwards as it only appears on pictures taken on the 15th of September and is gone in photos from the 16th of September.
Further changes include the addition of an armored cover for the M3 air intake on the engine deck. A change in the casting of the rear of the hull and the replacement of the pepperpot exhaust, which were ill suited to the task and caused problems of serious overheating of the rear decks of M3s. These changes required an adjustment in the tool stowage positions.
The rear deck showing the unarmored air intake inherited from the M3.
The rear deck showing the unarmored air intake inherited from the M3.
The co-driver also received a roof hatch with the removal of the rotor sight. The hinges of the hull hatches were moved forward from their original position at the rear of the hatch. The circular armor protection for the antenna mount above the SRC 506 radio was replaced with a hull ventilator and another ventilator was added just behind the turret and another fitted in the turret roof.
The welded hull pilot constructed by the Rock Island Arsenal has become somewhat of a mystery, no photos have (to date) been found of the completed pilot and only one picture seems to exist of a scale model of the vehicle. Interestingly, it includes the co-drivers hatch and does not have the side sponson doors and also included the later M34 gun shield.

It should be noted that the T6 was not the only horse in the race to replace the Medium Tank M3. In June 1941, three months before the T6 was completed, the Canadian built pilot of the Cruiser Tank Ram was completed and arrived for testing at APG in August. Before the first M4 had rolled off the production lines, 110 Rams had been built by the end of February 1942.
The Ram used the entire lower hull and running gear of the M3 with little or no changes. It utilized a smaller turret ring than the T6, only 60” (1524 mm) as opposed to the 69” (1752.6 mm) in the T6, which left the turret described as “cramped” and unsuitable for anything larger than the QF 6pdr fitted. As such, the Ram was considered unsuitable for combat by both the Americans and the British after trials at APG, but it served successfully as a training vehicle and as a base for a number of specialist vehicles.


T6 Medium prototype by David Bocquelet

Conclusions

On the 11th of December 1941, the welded hull version was designated the Medium Tank M4 and the cast hull the Medium Tank M4A1. Construction of the initial production pilots commenced in November 1941 and full production of the Medium Tank M4 began in February 1942. The last known reference to the T6 was in February 1947 in a picture showing it fitted with a potential field modification for additional armor protection for the differential housing. It is likely that the T6 was scrapped during the Korean War era “scrap drives,” but there remains a small hope that it survived and is still waiting to be rediscovered in some forgotten corner of APG.
The Canadian built Ram pilot undergoing automotive trials at APG.
The Canadian built Ram pilot undergoing automotive trials at APG.

Sources

Sherman: A History of the American Medium Tank, R.P. Hunnicutt
The T6 Medium Tank on The Shadock
Armored Thunderbolt, Steven Zaloga
AFV/G2 T6 Mockups, Chris Benedict

Medium Tank T6 specifications

Dimensions 5.6 x 2.6 x 2.9 m
18’4” x 8’6” x 9’6”
Total weight, battle ready 27.2 tonnes (60,058 lbs)
Crew 5 (Commander, Driver, Co-Driver, Gunner and Loader)
Propulsion Wright (Continental) R975 EC2, 9 cylinder radial
Speed (road) 38.6 km/h (24 mph)
Range 193 km (120 miles)
Armament 75 mm Gun M2 with 75 rounds
5 x .30 MG M1919A4 machine-guns with 10,000 rounds
Armor Maximum 76.2 mm (3”)
For information about abbreviations check the Lexical Index


This picture dated 7th April 1941 (although this date cannot be confirmed and May would be more likely) of the wooden mock up showing the little known 75mm and 37mm combination and a wider turret than the final design. The cut out in the upper right front of turret is possible a gunner’s sighting periscope. Although the twin bow machine gun apertures are present there is no flexible bow machine gun and no obvious vision device in the front right hull it would seem at this stage no co-driver was planned. The driver’s hatch appears to roll backwards unlike the later hinged hatches.

In this right side view of the early version T6 the right hand side sponson door is missing further adding to the argument for no co-driver.

The last known picture of the T6 taken on the 18th February 1947 with a prototype field expedient armor upgrade for the differential cover.

The new turret design with the pistol port and Protectoscope vision device.

The only known picture of the Rock Island Arsenal welded hull pilot (albeit a scale model) showing some of the design changes from the original cast hull pilot.

A practical demonstration of the floor escape hatch located behind the co-driver’s seat.


Rear view shower the pepperpot exhausts (1) that would soon be discontinued due to overheating of the rear deck area and the original straight edge casting that would be changed on the production models.

This picture clearly shows the reason for the removal of the forward hull mounted antenna which could easily be entangled with the main gun when traversing the turret.


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American M4 Sherman Tank – Tank Encyclopedia Support Shirt

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Categories
WW2 US Other Vehicles

Assault Tank M4A3E2 Jumbo

USA (1944)
Assault tank – 254 built

In early 1944, the United States Army decided that they needed an up-armored version of a medium tank for an assault role for the upcoming operations in the European Theatre of Operations (ETO). However, they had rejected previous plans for such a vehicle, and time was short. As the new T26E1 would not be ready in time and previous designs had been totally unsuitable for the task, the decision was made to modify the standard US Army medium tank of the time, the M4A3 Sherman.
The vehicle became the M4A3E2 Assault tank or Sherman Jumbo. With only 254 built, it represented less than 1% of the total build numbers for the M4. However, it’s iconic profile left a lasting image that is probably one the most easily recognized M4 variants.
It should be noted at this point that the name ‘Jumbo’ doesn’t appear in any wartime documentation and is almost certainly a post-war nickname, quite possibly created by a model company.
The only running Jumbo, restored by Jacques Littlefield and now operated by the Collings Foundation - Source: Auctions America
One of the only two running Jumbos, restored by Jacques Littlefield and now operated by the Collings Foundation – Source: Auctions America

Development

In February 1942, the British tank mission in the United States approached the US War Department with the idea of developing a heavy version of the soon to be produced M4 to meet the expected requirement for assaulting fixed enemy defensive lines. It’s likely that the British plan was to ask the Americans to cast a heavier version of the M4A1 by increasing the casting thickness up to 3 ½” (89 mm) on the glacis (front upper hull plate) and 3” (76 mm) on the sponsons (side upper hull plates).
Although this early plan came to nothing, the US Ordnance Department didn’t entirely forget about the idea and on 17th December 1943, the General Motors Proving Ground was directed to test an M4A3 with additional loading to a weight of 82,600 lbs (37466 kg). After 500 miles, it was found that “no abnormal failures were encountered. It, therefore, appears feasible to convert a medium tank to an assault tank with a weight of 82,600 lbs. If only limited operation is to be encountered.” This was therefore intended as a vehicle to be used on an as-needed basis and not for long periods of time or distance.
The M4A3 test tank with ballast fitted on 18th January 1944.
The M4A3 test tank with ballast fitted on 18th January 1944. The recently developed extended end connectors were fitted and helped to reduce the ground pressure even with all the additional weight. These extended connectors replaced the standard connectors that were used to join the individual track shoes together and added extra width to the track to disperse the weight of the vehicle. They were often called ‘grousers’.
Meanwhile, the Armored Fighting Vehicles and Weapons section (AFV&W) of the US Army European HQ put in an urgent request in January 1944 for 250 heavy tanks for the upcoming campaign in Europe. The request was based on the need for a tank to breach the Siegfried line. The following month, the Development Division of the US Army Ground Forces (AGF) agreed, but as the new T26E2 heavy tank was not expected until the following year, it was recommended that an expedient design should be based on an up-armored M4A3 medium tank. An alternative was offered by the Ordnance department, which proposed the old M6 heavy tank be modified to fulfill the role. The Ground Forces opposed this option because of the many problems of the M6 that were exposed during trials.
In March 1944, all parties agreed that the best solution was the up-armored M4 assault tank. On 2nd March, the Ordnance Technical Committee recommended that “the M4A3 with heavier armor be designated Medium Tank M4A3E2.” An order for 250 vehicles with 4 pilot vehicles was recommended and on 23rd March the order was approved. They were to be available to the army by August 1944. The contract was awarded to the Fisher Body Corporation in Detroit.
In an unusual move, Fisher was notified in late March that “in order to expedite delivery of the M4A3E2 Assault Tanks, certain requirements of applicable specifications will be waived for the total of 254 vehicles”. Put simply, the US Government trusted Fisher to do the job to the standard required without the need for the normal and rather time-consuming testing regime. This explains how the tank maintained its ‘E’ number designation. The letter ‘E’ stood for experimental and if the Ground Forces found the vehicle unfit for task, Fisher would still have been paid for all 254 ‘experimental’ vehicles which then would have remained in the US. As it was, all vehicles were provisionally accepted and 250 were authorized for overseas shipment at the end of May 1944.

Specifications


The M4A3E2 was to have an additional 1 ½” (38 mm) of armor plate welded to the upper hull front and sides, taking the overall thickness to 4” (101 mm) on the front and 3” (76 mm) on the side. The rear upper hull and top were unchanged, as was the lower hull. To ensure a good weld the additional side armor was welded in two pieces with a 2” (50 mm) gap in a vertical center line filled with weld. The additional plate had a keyhole cut into it to allow fitting over the existing bow machine gun ball mount. The standard beading that the dust cover fitted to was then welded to the new plate. The normal lights and sirens were not fitted. The 75 mm gun travel lock was fitted on 3” (76 mm) spacers.
Union Steel foundry was subcontracted to cast a heavier final drive assembly cover. The new casting was 3000 lbs (1360 kg) heavier than the standard and had a thickness that varied from 4” (101 mm) to a maximum of 5 ½” (139 mm). The new casting had to have a substantial ridge along the upper edge to allow for the fitting and bolting to the upper hull.
Pressed Steel Car was subcontracted to assemble and finish the turrets and gun mounts with the actual casting being done by Union Steel and Ordnance Steel foundries. The turret was based on the T23 76 mm turret with a similar internal layout and a full basket, but the pistol port was eliminated. The thickness was approx 6” (152 mm) all around but it did reduce to 2 ½” (63mm) at the rear below the bulge.
The 75 mm gun was installed in a modified M62 Gun Mount normally used for the 76 mm gun. An additional 5” (127 mm) of armor plate were added to the M62’s original 2” (50 mm) cast gun shield, creating a huge mantlet covering nearly ¾ of the turret front. This modified mount was designated ‘Combination Gun Mount T110’. The completed turret weighed in at an impressive 20,510 lbs (9303 kg), roughly 5000 lbs (2267 kg) heavier than the original T23 turret casting. The gun shield alone was 1100 lbs (498 kg) heavier than the standard shield.
Combat load included 104 75 mm rounds for the main gun, 600 rounds for the .50 caliber, 6250 rounds for the .30 caliber, 900 rounds of .45 caliber, 18 hand grenades and 18 2” smoke rounds.
To allow for all the additional weight of the tank, extended end connectors were fitted as standard to the tracks. These increased the ground contact by nearly 10% and kept ground pressure to a fairly reasonable 14.2 psi, compared with 13.7 psi for a standard M4A3 without extended end connectors. Although the original Ford GAA V8 powerplant was retained, the final drive ratio was increased to 3.36:1. This reduced the top speed to 22 mph (35 km/h), but the tank maintained reasonable acceleration even though it now weighed 84000 lbs (38101 kg). It could climb a 60% slope, cross a 7’6” (2286 mm) trench, climb a 24” (609 mm) vertical wall and ford 36” (914 mm) of water.
Fisher completed production in July 1944.

cobra King forst in Bastogne poster
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Testing

On the 8th June, tank 50326 was shipped to the Chrysler Tank Arsenal Proving Ground in Detroit for endurance trials. After some 400 miles which resulted in one broken spring it was however noted that the same “low milage failures had been experienced with standard weight vehicles”. It was apparent though that the additional weight of the Jumbo was seriously taxing the standard vertical volute suspension of the M4.

The difference can be seen between the three different bogie sets in the picture taken at Aberdeen. The middle and front bogies are clearly overloaded with the front set arms almost horizontal. As a result, the following order was issued “One thing that users must realise is that, in rough cross-country operation, the front volute springs will fail if permitted to ‘bottom’ violently”.
After the endurance test, tank 50326 was sent to Aberdeen Proving Ground (APG) for ballistic testing. As these tests took place in September 1944 some time after the M4A3E2 was released for overseas shipment the tests were for “information purposes only”. The tank was tested to destruction.

Operational service

The first vehicles arrived in the New York port on the 14th of August 1944. On the 29th, the 12th Army Group was informed by the War Dept that 250 M4A3E2 Assault tanks had been released and would be in the ETO in September. On the 1st September, the 3rd Armored Division put in a request for 150 M4A3E2s from 12th Army Group. The first 128 Jumbos arrived in France via Cherbourg on the 22nd September 1944.
Full records of exactly how the Jumbos were issued are difficult to identify as the tank were often only recorded as ‘Medium Tank M4A3’ with no distinction between a standard M4A3 and an M4A3E2. But partial records have been traced although some do seem to conflict. The first thirty six tanks were issued to the US First Army on the 14th October and were then issued to individual tank battalions. Fifteen to the 743rd, fifteen to the 745th and six to the 746th. On the 18th October, Normandy beach depots recorded having seventeen on hand, twenty four released to Armies and nineteen on route to Third Army. By the 24th October Army allocations for delivery had been confirmed as:
First Army – 105 M4A3E2 Jumbos
Third Army – 90 M4A3E2 Jumbos
Ninth Army – 60 M4A3E2 Jumbos
Clearly someone at 12th Army Group needed a little extra work on their basic maths!
The last recorded delivery was on the 9th November when 746th Tank Battalion of the First Army was issued a further nine Jumbo’s.
The tanks were well received and the advantages of the additional armor were quickly appreciated. Jumbos were chosen to be the standard point tank any time advances were made with opposition expected.
A 76mm armed Jumbo of the 3rd Armoured Division, Cologne, 6th March 1945.
A 76 mm armed Jumbo of the 3rd Armoured Division, Cologne, 6th March 1945.
Crews did still feel the need to add more armor and sandbags were a common addition to the glacis and in a few cases concrete was used. The additional weight of 4”-6” (101-152 mm) of concrete right on the nose of the tank must have made it a very difficult proposition to drive. The front bogie was almost certainly beyond its maximum weight capacity by that point and a mechanical failure on the front bogies was most likely a case of when, not if.
M4A3E2 of 743rd Tank Btn, Altdorf, 27th November 1944. Sandbags covered with hessian and possible turf on the glacis.
M4A3E2 of 743rd Tank Btn, Altdorf, 27th November 1944. Sandbags covered with hessian and possible turf on the glacis.
M4A3E2 with concrete applique on glacis, date and location unknown (frame from a US Army Signal Corp film
M4A3E2 with concrete applique on glacis, date and location unknown (frame from a US Army Signal Corp film)
Because of the nature of their employment, the Jumbos suffered heavy losses. The 4th Armoured Division alone recorded 24 M4A3E2s lost in action in their after action report at the end of the war. Twenty four lost in one division may not sound like a lot, but when it is considered that nearly 10% of the total production run of the vehicle was lost in one division it shows they clearly bore the brunt of the fighting wherever they were present. Even with all the additional armor, Jumbos were still as vulnerable to mines as any other tank (minefields often covered approach routes to German positions) and concentrated anti-tank gun fire.
This Jumbo of 743rd Tank Battalion was knocked out on 22nd November 1944 near Lohn, Germany.
This Jumbo of 743rd Tank Battalion was knocked out on 22nd November 1944 near Lohn, Germany. It was hit by four 88 mm rounds from an anti-tank gun 800 yds (730 m) away. One bounced off the glacis plate and two off the manlet before the fourth actually penetrated through the gunners telescope opening (chalked ‘9’ by Divisional Intelligence staff).
Another Jumbo of 743rd Tank Battalion also knocked out in the same operation.
Another Jumbo of 743rd Tank Battalion also knocked out in the same operation. This one was disabled by a ‘friendly’ mine and abandoned by its crew with no casualties. After it was abandoned the Germans concentrated anti-tank fire on it to ensure it wasn’t recoverable.
During February 1945, approximately 100 M4A3E2s were upgunned to 76 mm using guns recovered from knocked out 76 mm armed M4s and normal supply stocks. This upgrade was a fairly straight forward field modification, as the combination gun mount was originally designed for this gun. The more complicated part of the conversion was the modification of the main gun ammunition stowage. This required removing the turret and the fitting of 76 mm racks in place of the shorter 75 mm racks. These replacement racks were then secured in place with a series of fabricated welded braces. Records indicate that conversion took 75 man hours per tank.
Out of the 250 sent to Europe, today there are believed to be eight complete survivors and one further hull and turret. Of the four test vehicles that remained in the States, none survived. Of these four, only one cannot be positively accounted for. The first was destroyed during impact testing as stated above. The second was used as a post war test bed for two different flame thrower tanks and was then used as a range target at Ft Knox. The third was sent to the Aberdeen Proving Grounds for additional testing. Its disposition is unknown but it was likely scrapped.
As for the fourth, it was last reported in a depot in Pennsylvania in 1945. It may still be somewhere awaiting discovery but in all likelihood it was also scrapped.
This up armored M4A3 (76) HVSS of the 4th Armoured Division shows the addition of armor plate to the glacis and turret.
This up armored M4A3 (76) HVSS of the 4th Armoured Division shows the addition of armor plate to the glacis and turret.
Alongside the up gunning of the Jumbo’s, the 12th Army Group commissioned the building of what became known as Field Expedient Jumbos. These were M4A3 (76) HVSS (often called M4A3E8s or Easy Eights) with additional armor welded to the glacis and turret. These tanks often achieved very near levels of armor to the original Jumbos. The additional armor was scavenged from wrecked tanks. Other M4s and Panthers were preferable. Entire glacis plates from wrecked M4s could be cut out and welded to the new vehicle without needing to move gun travel locks or cutting new apertures for the bow machine-gun. Much of this work was carried out by three civilian factories with an allowance of 85 man hours per vehicle.
A report from the 6th Armoured Division noted the success of these Expedient Jumbo’s. ‘A recently modified M4A3E8 took a direct hit from a German 75 mm shell with the only resulting damage being the complete separation of the middle section of additional armour from the hull. The tank continued in the action and succeeded in “knocking out” the opposing vehicle.The crew whose lives were saved by this additional protection were loud in their praise of this modification.

M4A3E2 Houffalize jan 1945
M4A3E2 “Jumbo” from the 33rd Battalion, 3rd US Armored Division, Houffalize, Belgium, January 1945.Cobra King Sherman M4A3E2
M4A3E2 Jumbo “Cobra King” with the “First in Bastogne” inscription, probably the most famous Jumbo of the entire 4th Armored Division.

M4A3E2(76)W jan 1945
M4A3E2(76) Jumbo from the 37th Tank Battalion, 4th Armored Division, Alez, Germany, March 1945.

Colonel Creighton Abrams
Colonel Creighton Abrams’ “Thunderbolt VII” and his famous personal insignia, Horazdovice, May 1945. This vehicle was a prime example of a Field Expedient Jumbo, being an Easy Eight with added armor.

Cobra King

Without doubt the most famous of all the Jumbos was named ‘Cobra King’, the first tank into Bastogne in Belgium, the vital crossroads town at the centre of the fighting during the Battle of the Bulge.
Cobra King was issued to 37th Tank Battalion of the 4th Armoured Division on the 24th or 25th of October 1944 and was assigned as the company commander’s vehicle of Company C. Much detail of Cobra Kings war service is difficult to confirm with absolute certainty but some of it is as follows.
From the time of its issue to its loss near the end of the war, Company C had five commanding officers who were all therefore Cobra King’s commanders.
July 1944 – 23rd November 1944, Richard Lamison
23rd November – 23rd December, Charles Trover (Trover was killed in action 23/12/44)
23rd December – 12 Januar 1945, Charles P. Boggess
12th January – (?), George Tiegs
(?) – 28th March 1945, William Nutto
Before the Battle of the Bulge details, of Cobra King’s actions are difficult to confirm. A well known one is on the 7th November outside Fontany, France when during an attack Cobra King took a hit to the final drive assembly that disabled the tank and left it with a permanent battle scar.

The splash damage left from the penetration of the final drive assembly - Picture: Don Moriarty
The splash damage left from the penetration of the final drive assembly – Picture: Don Moriarty
During the German winter offensive, the Battle of the Bulge, the important crossroads town of Bastogne, Belgium had been cut off and surrounded by German forces. Patton’s Third Army was tasked with trying to break through the German lines in the south with the 4th Armored Division as the main spearhead of this counterattack. On December 26, 1944, Lt. Boggess, commander of Cobra King, was fighting his way on the road from Assenois, Belgium to Bastogne. The following passage is from an article written by Charles Lemons, former curator of the Patton Museum.
Cobra King was way ahead of the rest of the column and had just destroyed a German bunker along the road when Boggess spotted several uniformed figures in the woods near the bunker. They wore the uniforms of U.S. soldiers, but knowing how Germans were disguising themselves as Americans, he maintained a wary eye. He shouted to the figures. After no response, he called out again and one man approached the tank. “I’m Lieutenant Webster of the 326th Engineers, 101st Airborne Division. Glad to see you.” With that meeting at 4:50 p.m. on December 26, 1944, Patton’s Third Army had broken through the German lines surrounding Bastogne
Cobra King
Cobra King
While records of the rest of the crew are not so complete the crew during the Battle of the Bulge is known.
Gunner, Milton B. Dickerman
Loader, James G. Murphy
Driver, Hubert J.J. Smith
Co-Driver, Harald D. Hafner
Cobra King was one of the Jumbos to receive a 76 mm gun upgrade and it’s coaxial machine-gun was also upgraded to a .50 cal (12.7 mm) in early 1945. The next part of Cobra Kings known service followed in March. More from Charles Lemons article.
After doing more research and discovering a post-war photo of an M4A3E2 Jumbo at a repair depot in Lager Hammelburg that had matching characteristics of Cobra King, the theory was presented that this was Cobra King and that it had participated in “Operation Hammelburg” the controversial mission which was personally ordered by Third Army commander General George S. Patton.
The operation took place on March 26-28, 1945 with the official purpose of liberating a prisoner of war camp, OFLAG XIII-B, near Hammelburg, Germany. But unofficially, it’s purpose was to free Patton’s son-in-law, Lieutenant Colonel John Waters, who was taken prisoner at Kasserine Pass, Tunisia, in 1943.
A small task force comprised of men and vehicles from the 37th Tank Battalion and 10th Armored Infantry Battalion commanded by Captain Abraham J. Baum, was formed. Task Force Baum consisted of M4A3 Shermans, M5A1 Stuarts, M4/105 Shermans, Jeeps and halftracks. The total strength was 314 men and 57 vehicles.
The task force fought through German lines with serious losses and reached Hammelburg and liberated the camp, but Patton’s son-in-law was wounded and had to be left behind. Ultimately, the entire operation turned into a total failure when German forces in the area eventually overwhelmed the small task force, destroying or capturing all vehicles and capturing Baum and almost all of his men and the liberated POWs.
Since Company C of the 37th Tank Battalion was in this raid, it leads to the question – did Cobra King participate in the ill-fated Hammelburg mission? In the book RAID!: The Untold Story of Patton’s Secret Mission by Richard Baron, Major Abe Baum and Richard Goldhurst, Baum stated that a tank named “Cobra King” commanded by Lt. Nutto was knocked out and abandoned on March 27, 1944 as it approached Hammelburg. But some historians have discounted this entry citing that the need for speed was essential on this mission and that a heavy, slow-moving Jumbo would be a hindrance.
Through these observations of Cobra King and research, then Patton Museum curator Charles Lemons proposed at the time the following:
“Cobra King is slowly revealing its secrets. The Patton Museum staff and volunteers have been brain-storming over the implications of what we have been finding. We all agree that this is “Cobra King” – no doubts what-so-ever. What the big question has been – what happened to the tank after December 26, 1944.”
“We can safely state that the vehicle remained in the 4th Armored Division – and remained as the command tank for Company C until its demise in combat. Yes, in combat – in fact the information we have indicates that the vehicle met its end in March of 1945. We firmly believe that Cobra King was lost with the rest of Company C, 37th Tank Battalion, and Task Force Baum, on the raid on Hammelburg.”
“Reminiscences from then Captain Baum, as written in the book “RAID!”, place Cobra King at the assault on Lager Hammelburg, where it was hit and put out of action. Unfortunately, Abe Baum does not note the damage.”
“However, what we have for Cobra King is a busted #3 road wheel assembly on the left side and evidence of a fire and subsequent small arms ammunition cook-off inside the BOG (bow gunner/co-driver) position. We have a vehicle that was recovered and taken to, of all places, Lager Hammelburg, where it was left in the yard until the mid-1950s.”
Further research by Don Moriarty has revealed that it is likely that Cobra King was actually hit by a Panzerfaust as the convoy was preparing to leave the camp not on the approach as originally thought. It is likely that this was the cause of the damage to the number three left side bogie station. The internal fire is not now thought to have happened at the time of the raid. As there was no main gun ammunition in the tank at the time of the fire and only machine-gun ammunition, it is believed that the Germans attempted to destroy Cobra King by torching her as the 14th Armoured Division approached Hammelburg in April 1945 to prevent it falling back into US hands in an operational condition.
“Further, C Company was only informed less than a day before the action, having been selected because it had the most tanks of the battalion. No commander would have abandoned one of his strongest vehicles – a Jumbo with a 76 mm main gun and .50 caliber coax – nor could he abandon his own command vehicle. Interviews with Brigadier General Jimmie Leach, B Company Commander, 37th Tank Battalion, show that even when in a hurry the tanks rarely traveled faster than 15 mph to avoid losing the infantry support, so a marginally slower vehicle wouldn’t have mattered.”
“Hammelburg was in the Seventh Army zone of control and 4th Armored Division, under Third Army, never came within 40 miles, with the exception of Task Force Baum. So how would a 4th Armored Division vehicle (Cobra King) end up in a Seventh Army repair facility?”
After the war, Cobra King became a monument tank, put on display at various American bases in Germany, Kitzingen (Harvey Barracks), Crailsheim (McKee Barracks), Erlangen (Ferris Barracks), & Vilseck (Rose Barracks) where it remained in obscurity, the wrong registration number painted on its side from one of its numerous repaints. In May 2001, Army Chaplain Keith Goode was checking out monument tanks while serving in Germany.
He was locating serial and registration numbers of Sherman tanks on U.S. Army bases. He passed the information onto the G104 Sherman interest group in the U.S. where member/historian Joe DeMarco confirmed that the tank was indeed the actual Cobra King.
After learning this information, another member of G104 stationed in Germany, Sgt. Brian Stigall of the Fifth Battalion, Seventh Air Defense Artillery and Steven Ruhnke, First Armored Division museum curator, paid Cobra King a visit and also confirmed the serial number and passed the information up the chain of command.
Along with other Army historians, including Patton Museum curator Charles Lemons, the identity of Cobra King was officially confirmed. Cobra King was then shipped to the United States and on to the Patton Museum’s workshops on July 9, 2009 for restoration.
Cobra King mid restoration - Source: Don Moriarty
Cobra King mid restoration – Source: Don Moriarty
At first, the plan was to restore the interior and exterior to the way Cobra King looked on December 26, 1944. However, this plan was altered due to findings in the interior of the tank. It was decided by the then Patton Museum director Len Dyer that the exterior of Cobra King would be restored to how she looked during the Battle of the Bulge, but that the interior would be left showing interior modifications to ammo storage and the damage sustained presumably at Hammelburg.
Four Patton Museum volunteers, Don Moriarty, Garry Redmon, Coleman Gusler and Robert Cartwright were selected to work with museum staff on the restoration along with other volunteers who also contributed to the restoration.
After a two-year exterior restoration, Cobra King was as finished as possible before she was shipped out to her new home at Fort Benning, Georgia in August 2011. – Patton Museum curator Charles Lemons
Cobra King on completion of restoration with the original 75mm gun returned - Picture Don Moriarty
Cobra King on completion of restoration with the original 75mm gun returned – Picture Don Moriarty
Today another Jumbo is in the town of Bastogne. It is not Cobra King, but it is painted in its markings in honor of this famous tank. It is however now missing its extended track end connectors. It is the only surviving Jumbo outside of the United States now that the real Cobra King has been returned to the States.
The only Jumbo in Europe, from the Belgian Tank Museum.
The only Jumbo in Europe, from the Belgian Tank Museum.

Conclusion

The overall effect of the E2 program was positive. It addressed the very real concerns of the crews that the M4 lacked the armor protection that enemy tanks had. It produced a tank that the Germans had a much harder time dealing with than they were used to. One thing unknown is the moral effect (if any) this had on German crews, as at normal combat ranges the Jumbos would have been difficult to distinguish from standard M4s and the effect of seeing your shots, that would normally disable or knock out a tank, having no effect cannot be a comforting sight!
An article by Adam Pawley

Sources & Links

Don Moriarty
Sherman: A History of the American Medium Tank, R.P. Hunnicutt
Armoured Thunderbolt, Steven Zaloga
Sherman Minutia
Charles R. Lemons
Garry Redmon
Armor for the Ages

M4A3E2 specifications

Dimensions 6.3 x 2.9 x 2.9 m
20’8” x 9’6” x 9’6”
Total weight, battle ready 38.1 tonnes (84,000 lbs)
Crew 5 (commander, driver, co-driver, gunner and loader)
Propulsion Ford GAA V8, 500 [email protected] rpm
Speed (road) 35.4 km/h (22 mph)
Range approx 160 km (100 mi)
Armament 75 mm (2.95 in) Gun M3 or 76 mm (3 in) Gun M1 with 104 rounds
.50 (12.7 mm) HB M2 machine gun, 600 rounds
.30 (7.62 mm) M1919A4 machine-gun, 6250 rounds
Armor Maximum 177 mm (7”)