There are not many tracked vehicles designed to work underwater, and whilst these might not fall into the usual category of what people consider ‘tanks’, they are worthy of consideration by anyone serious about tracked vehicle technology. The underwater realm offers challenges unique to vehicles whether they are armed and armored or not.
This unusual vehicle was the brainchild of Captain Jesse Wilford Reno (4th August 1861-2nd June 1947), an American inventor from New York, whose most famous contribution to western culture was not a tracked machine, but the escalator, invented in 1899. As an anecdote, his father, Major General Jesse Lee Reno, a Union General in the American Civil War, had Reno, Nevada, named after him. In addition to this, in 1919, Mr. Reno saw an opportunity to put his inventive mind to use; he built an underwater machine designed for salvage operations.
In 1919, underwater operations were still extremely hazardous. The personal diving suit was a huge, clumsy and dangerous affair, and submarines were in their infancy, with numerous accidents still occurring. The depth to which many of these early underwater pioneers could venture was extremely limited and, therefore, salvage at even a nominal depth at the time was impossible. Reno was therefore correct in assessing an important commercial market for a machine able to operate at depth and salvage valuable cargoes from sunken vessels.
The design was a simple one, basically being a sealed and heavily protected cylinder, capable of withstanding external water pressure, mounted on tracks for mobility. Large enough for up to two men, the cylinder measured some 6 feet (1.82 m) in diameter and 8 feet (2.44 m) in height according to the patent. During the recovery of the ‘Scally’, which sank in 1923, the Reno Underwater Tractor was described as being 7 feet (2.13 m) in diameter and 9 feet (2.74 m) tall, weighing some 18 tons (16.3 tonnes).
Air supply was provided by the ‘mother-ship’, which delivered air for the occupants of the vehicle but also compressed air which was to be piped into a large buoyancy sack attached to the sunken vessel or part of it. That buoyancy sack would then rise to the surface for recovery. This is still, to this day, effectively the same means by which things are raised from the sea. The mother ship also provided an electrical supply for the vehicle by means of the same umbilical cable down which air was pumped. This electrical power was used for lighting and also to power the equipment in the vehicle. Vision from inside the machine was limited to just a small glass porthole in each ‘side’ of the cylindrical chamber. Access was only possible via a single circular hatch on the roof of the machine.
For raising a sunken vessel, the machine would simply be used to connect a series of buoyancy sacks along the exterior of the vessel which, once filled with air, would bring the whole ship either to the surface or just off the sea-floor so it could be towed to shallower waters for salvage. Additionally, clever knowledge and use of the tides could be used to raise the ship, move it to shallow water and then resink at high tide, whereby it would be exposed by the receding waters.
Air Bags and the Cannon
The ‘airbags’ were, in fact, large steel boxes into which the air was pumped, but the question was how to attach these buoyancy devices to the hull of the ship. Each one would be exerting a lifting force of 300 tons, so the connection had to be extremely strong. The solution Reno settled upon was that of hooks which would be fastened into the side of the sunken vessel’s hull.
The question, therefore, was how to make holes in the side of sunken vessels. In his original 1919 Patent, he determined that it should be made by means of a drill rotating within a water-tight coupling. This drilling system though, was after he had already submitted a patent application for the concept of using a gun to make the holes.
The hole would be made by firing a horizontally mounted gun using compressed air. The calibre of this air cannon was given as 4” (101.6 mm) of an unspecified “well-known type” firing a pointed solid steel slug through the outer hull of the sunken vessel to make a hole for the attachment of buoyancy bags/boxes. The barrel of this gun was supported by the walls of the crew chamber through which it was projecting and was fitted with crude ‘stuffing boxes’ acting as the recoil buffers. As drawn, this arrangement was hazardous and likely to violate the watertight nature of any seal around that gun. In his submission, Reno mentions that he considers a gun using the ‘Davis’ principle to balance the recoil of the gun. The shell was only to be fired with enough force to rupture the side of the hull without causing damage to the interior of the ship, although quite how this was to be calculated is unclear. With up to 50 holes needed per side or a hole every ten feet (~3 m) by Reno’s calculations, a large number of projectiles would have to be carried in order to perform this means of hole-making. The fact that a month after this ‘gun’ idea had been submitted he had switched to a drilling system demonstrates that even he understood the impracticality of this underwater cannon concept. When Reno’s machine was used in 1923, it was using not one but two 4” (101.6 mm) diameter drills.
The vehicle itself was described as an ‘endless track tractor’ or ‘mobile tractor’ consisting of a large watertight cylinder mounted on a low pair of tracks. No suspension was provided in the track run on either side which was made from two large wheels, one at each end, separated by 5 smaller wheels. All were attached to a rigid horizontal frame. Drive for the tracks was delivered to the rear-most wheel via a drive chain running from a small motor estimated to be just 20 hp or so mounted inside the steel chamber. Each track was driven independently with the clutch controls worked from a small handwheel. This level of control over the drive to each track was complex but allowed for fine manoeuvering. The operator, who would also have to drive the machine, could maneuver by means of clutches that could engage and disengage with the tracks. Engaging the right track, the machine would move to the left and vice-versa.
On the outside of the chamber was a pressurized hose that could be manipulated by the operator to blast away sand, dirt, and debris from his locale, allowing him to work clearly on the side of the vessel. The chamber itself was divided into two portions. The lower part was attached to the tracked chassis and contained the motor and driveshaft. The upper part of the chamber contained the operator and controls and could rotate, allowing the machine to use its drills against the sides of the ships it was salvaging.
The tractor unit could not float or ’swim’ and was simply lowered to the sea bed by chains from a hoist where it had limited movement, but it had proven itself to be a viable system. Reno’s underwater salvage firm employed his salvage methods successfully in the 1920s and 30s. It was used in the Baltic for the Estonian government reclaiming parts from the 15,000 ton Russian battleship ‘Slava’ from a depth of 40 feet (~12 m), and closer to home with the recovery of the 500-ton Coast Guard cutter ‘Scally’ which sank off Long Island Sound in 65 feet (~19.8 m) of water. Reno’s suggestion of using this method to raise the Lusitania was not, however, ever taken seriously.
Reno never described his underwater vehicle as a tank. He did have other military ideas but not for this vehicle, although it has appeared subsequently online as some form of underwater tank akin to a Tauchpanzer. The machine was tracked, and potentially armed with a cannon, but it was not a military vehicle. Despite this, the design is an interesting one and important in regards to the development of tracked vehicles as it is likely the first underwater tracked vehicle ever built. It was certainly not to be the last, with both Great Britain and Germany looking at tanks which could drive on the sea-bed in WW2. What became of Reno’s underwater vehicle is not clear, likely it was simply scrapped though, as diving technology caught up through the 20s and 30s. Jesse Reno was inducted into the National Inventors Hall of Fame in 2007 for his work on the escalator and died in 1947, leaving behind a legacy of inventions well known, like his escalator, and obscure, like his underwater tractor.
Illustration of Reno’s Endless Belt Tractor or ‘Underwater Tank’ produced by Andrei Kirushkin, funded by our Patreon campaign.
2.5 x 2.74 x 2.5 meters
18 tons (16.3 tonnes).
1 – 2
400 feet (~122m)
drill or 4” (101.6mm) gun
US Patent US1523659 ‘Apparatus for Raising Sunken Ships’. Filed 25th November 1919. Patented 20th January 1925.
US Patent US1523660 ‘Apparatus for Raising Sunken Ships’. Filed 27th December 1919. Patented 20th January 1925
US Patent US136142 ‘Raising Sunken Vessels’. Filed 23rd February 1920. Patented 4th January 1921.
US Patent US1364143 ‘Raising Sunken Vessels’. Filed 2nd April 1920. Patented 4th January 1921.
US Patent US1416754 ‘Device for Raising Sunken Vessels’. Filed 17th March 1921. Patented 23rd May 1922.
US Patent US1400316 ‘Art of Raising Submerged Vessels’. Filed 13th June 1921. Patented 13th December 1921.
US Patent US 1495529 ‘Raising Sunken Ships’. Filed 2nd August 1923. Patented 27th May 1924.
Canadian Patent CA225695 ; Raising Wrecked Vessels’. 7th November 1922 Modern Mechanix January 1935 ‘Under-Sea Tractor-Sphere Roams Ocean Floor’ Modern Mechanix April 1932 ‘Submarine Safety: An Insolvable Problem?
Popular Science Monthly, September 1923 National Inventors Hall of Fame ‘Gunning Wrecks’ Therebreathersite.nl
Grohman, A. (2014). Salvage of the Scally. The Leader.
In 1944, the United States Army began testing British-built flail tanks such as the Crab and Scorpion. Mine flails like these consist of a rotating drum connected to a series of chains suspended from the front of the vehicle. The drum rotates at a high speed, causing the chains to pummel the ground, detonating any mines that may be buried.
Meanwhile, down on Maui, one of the Hawaiian islands in the central Pacific, members of the 4th Marine Division, United States Marine Corps (USMC), were recuperating from their time battling the Japanese on Saipan and Tinian. While on Maui in late 1944, the 4th Marines began to undertake experiments with their tanks, one of which was copying the Crab and Scorpion equipment they had seen in an article in an issue of ‘Armored Force Journal’ (or possibly ‘Infantry Journal’) that the division had received.
The result of this particular experiment was an improvised mine flail built using an old M4 Dozer and the back axle of a truck. While it was just an improvised vehicle built from scrap, it did make it to the ash-covered island of Iwo Jima. Its deployment there, however, did not exactly go to plan.
Guinea Pig, an M4A2 Dozer
The Marine Corps began to receive the M4A2 in 1943. The tank was of a welded construction and was 19 feet 5 inches (5.9 meters) long, 8 feet 7 inches (2.6 meters) wide and 9 feet (2.7 meters) high. It was armed with the typical 75mm Tank Gun M3 main armament. Secondary armament consisted of a coaxial and a bow-mounted Browning M1919 .30 Cal. (7.62mm) machine gun. Armor thickness was pretty standard for the M4s with a maximum of 3.54 inches (90 mm). The tank’s weight of around 35 tons (31.7 tonnes) was supported on a Vertical Volute Spring Suspension (VVSS), with three bogies on each side of the vehicle and two wheels per bogie. The idler wheel was at the rear. Average speed was around 22–30 mph (35–48 km/h). The big difference of the A2 with respect to other M4’s was the fact that it was diesel powered, unlike other models which were mostly petrol/gasoline driven. The A2’s powerplant consisted of a General Motors 6046, which was a twin inline diesel engine producing 375 hp.
Dozer tanks are used for route clearance. Dozer kits were installed on a number of different Sherman types in the Pacific, not just the A2. Others included the M4 Composites and M4A3’s. They were able to push debris off roads or clear routes through the dense jungles of the Pacific islands. The Dozer blade, known as the M1, was 10 feet 4 inches (3.1 meters) wide and was attached via long arms to the second bogie of the suspension. On the transmission housing on the bow of the host tank, a hydraulic ram was placed to allow the blade a small degree of vertical traverse.
After reading the article about the flail tanks the Army had tested, Robert Neiman, the Commander of C Company, 4th Tank Battalion decided that it would be a good idea for the Marines to develop their own version. Nieman discussed this with his Officers and NCOs who agreed with the concept. They knew that, in the coming battles, it was highly likely that they would run into dense Japanese minefields, and there were not always enough engineer personnel to clear them. The guinea pig for this experiment was a salvaged M4A2 dozer tank named “Joker” that had previously served with the 4th Tank Battalion on Saipan. It was available for this experiment as, at this time, the Marine Corps was starting to be re-equipped with the newer gasoline/petrol engined M4A3 model. The modifications were undertaken by Gunnery Sergeant Sam Johnston and Staff-Sergeant Ray Shaw who was also the chief maintenance NCO (Non-Commissioned Officer).
A new welded frame was constructed and attached to the joint on the second bogie. At the end of this frame, they placed a salvaged axle and differential from a truck. Drums were placed where the wheels once were and it was to this that the flail elements were attached. Approximately 15 elements were attached to each drum. The elements consisted of a length of twisted metal cable with towing eyes at the end, short lengths of chain, approximately 5 links in length, were then attached to this cable.
A drive shaft extended from the differential housing to the glacis of the tank and passed through the armor just to the left of the bow machine gun position. On the inside, this meshed with a salvaged transmission from a jeep which was, in turn, connected to the tank’s own drive shaft. This is what provided drive to the flail, allowing it to spin. The bow-gunner/assistant driver would be in charge of controlling the rotation and speed of the flail.
A frame was built atop the vestigial hydraulic ram left over from the tank’s time as a dozer. This frame supported the drive shaft, but also allowed the flail assembly to be lifted up and down. Additional support when lifting was provided by a metal shaft bolted to the glacis of the tank. It had a joint at the glacis end, with the other end connected to the frame near the axle – also jointed.
On completion of the vehicle, tests were authorized. Division commanders authorized the laying of a live minefield for the vehicle to carve a path through. In this initial test, the vehicle successfully beat a 30 to 40-yard (27 – 36 meter) path through the minefield. The tank emerged unscathed, the only real damage received was to the differential housing. Shrapnel from an exploding mine had penetrated the underside of the housing, but there was no internal damage. To stop this happening again, the engineers encased the housing in welded metal plating and during the following tests, no more damage was received.
Robert Nieman informed other Officers and his superiors of the success of the tests. Pretty soon, a display for high-ranking Officers of other units and branches stationed on Maui was arranged. However, come the morning of the display, the man with all the experience driving the thing, Gy.Sgt Johnston was, to quote Nieman; “drunk as a skunk”. Luckily, another driver was found for the display, which proved to be a great success. So much so, that it was planned to use this improvised vehicle with the 4th Tank Battalion in the coming assault on Iwo Jima.
Despite being the only one of its kind (and being a purely improvised vehicle), the flail tank was deployed during the February 1945 invasion of the volcanic island of Iwo Jima. It was assigned to the 4th Tank Battalion’s 2nd Platoon, under the command of a Sergeant Rick Haddix. It caused a small logistical issue, as it was the only Diesel engined tank the 4th Battalion took to Iwo.
Iwo Jima was both the first and last deployment of the vehicle. It is commonly thought that the tank simply bogged down in the soft ashen terrain of the island, as was the case with many tanks during the assault. In actuality, the fate of the vehicle was much more detailed than that. The Flail tank managed to advance to the island’s first airfield – simply identified as ‘Airfield No. 1’. Near the airfield was a series of flags, Sgt. Haddix believed these to be markers for a minefield and ordered the tank forward. These flags, however, were actually range markers for Japanese heavy-mortars in an elevated but hidden position nearby. The tank was pummeled by a barrage of mortar bombs, critically damaging the flail assembly and the tank itself. Following this, Sgt. Haddix and his men bailed out and abandoned the tank.
Thus ends the story of this improvised mine flail. Despite making it to one of the bloodiest battlegrounds of the Pacific Campaign, it never got a chance to prove itself. Robert Nieman was of the opinion that there needed to be more, which would likely have become a reality if American Forces had gone on to invade the Japanese mainland. Nonetheless, this improvised vehicle is a testament to Marine ingenuity. The Marines at this time were used to receiving the Army’s hand-me-downs, so the ‘make do and mend’ nature came naturally to these men. Although, by 1944, the Corps was getting what it requested from its own supply system. It is unclear what happened to the flail tank after it was abandoned. The most logical guess is that it would have been salvaged and scrapped during the post-battle cleanup.
Other US Flails
Neither the United States Army nor Marine Corps ever officially adopted a mine flail, although many were tested; some even in theatres such as Italy. The most produced flail was the Mine Exploder T3, a development of the British Scorpion, built on the hull of the M4A4 – a tank that otherwise went unused in American forces, other than in training units. Just like the Scorpion, the flail assembly was mounted at the front of the tank and was driven by a separate engine mounted externally on the right side of the hull, encased in a protective box. This engine drove the flail to 75 rpm. The Pressed Steel Car Company undertook the production of the T3 and would construct 41 vehicles in total. A number of these were rushed into theatre overseas in 1943. They went on to be used in the Italian Campaign, most notably in the Breakout from Anzio and the fight towards Rome. The flails were operated by men of the 6617th Mine Clearing Company, formed from the 16th Armored Engineers of the 1st Armored Division. The vehicles were eventually declared unfit for service as mine detonations frequently disabled the flail – the flail also limited the tank’s maneuverability.
An improved design for a flail was unveiled in June 1943, designated the T3E1. This vehicle was similar to the British Crab as the flail drum was propelled via a power-take-off from the tank’s engine. Although it was an overall improvement, it was still a failure and disliked by operators. This was mostly because the flail threw rocks and dust into the vision ports and because the flail unit was too rigid to follow the contours of the terrain.
When the Second World War ended, work on mine flails in the US ceased. With the eruption of the Korean War in June 1950, however, attention was again given to such vehicles. In preparation for deployment to the Korean Peninsula, engineers stationed in Japan began working on flails built on late-model M4s, namely the M4A3 (76) HVSS. The most common type to emerge featured wire cutters at each end of the drum, and 72 flail chains. Like the Scorpion flails, the drum was propelled by an external engine mounted in a protective box on the right side of the hull. Other flails were improvised in the field, but information on these is scarce.
Illustration of the Marine Corps’ improvised Mine Flail, built on the hull of a salvaged M4A2 Dozer, using a truck axle and a salvaged transmission from a jeep. Illustration by Tank Encyclopedia’s own David Bocquelet.
Dimensions (not including flail)
5.84 x 2.62 x 2.74 m
19’2” x 8’7” x 9′
Total weight (flail not included)
30.3 tons (66,800 lbs)
5 (commander, driver, co-driver, gunner, loader)
Twin General Motors 6046, 375hp
48 km/h (30 mph) on road
Vertical Volute Spring (VVSS)
M3 L/40 75 mm (2.95 in)
2 x (7.62 mm) machine-guns
Maximum 76 mm (3 in)
Robert M. Neiman & Kenneth W. Estes, Tanks on the Beaches: A Marine Tanker in the Pacific War, Texas A&M University Press
R. P. Hunnicutt, Sherman – A History of the American Medium Tank, Presidio Press The Sherman Minutia Evolution of Marine Tanks
Following the Allied invasion of Northern Europe in 1944, the US Department of Ordnance, believing that they would encounter heavily fortified areas such as the Siegfried Line further in northwestern Europe, decided there would be a need for a limited number of tanks with heavier armor and more powerful guns in order to act as breakthrough tanks. In order to get past these fortified areas, the M6A2E1 project was started, which would mount the turret of Heavy Tank T29 on an up-armored Heavy Tank M6A2 hull.
M6A2E1 initial draft design from July 1944; its similarity to the T26 turret is apparent here. Photo: History of the Heavy Tank, M6A2E1.
The Heavy Tank T29 had started its development during August of 1944 in response to the belief that the US would need heavily armored and armed vehicles to take on fortifications and enemy vehicles that would be encountered in the advance into Europe. However, the Heavy Tank M6 was chosen for this role instead as the T29 was still in early development and would likely not be adopted and available before the Allies encountered these heavier fortifications. Ordnance, having M6 tanks left over, decided that these could be modified to meet the needs. As such, it was proposed to modify the M6 to mount the T29 turret, and to increase its armor. To do so, the M6’s turret ring would be expanded.
The M6 was a US heavy tank designed in 1940 mounting a 76 mm and a 37 mm cannon. It was in trials by 1943 but never put into service. There were 3 sub-variants of the tank made. These being the M6, M6A1 and T1E1. The M6 and M6A1 were similar, only differing in the M6 being cast and the M6A1 welded. The T1E1 was similar to the M6 but had an electrical transmission instead of a torque converter type. It had been proposed to standardize the T1E1 as the M6A2 but this was not accepted. Despite this, the M6A2 name appeared in a number of drawings and correspondence concerning the vehicle.
To increase the armor of the tank, it was decided to remove the driver’s vision door along with the hull machine gun and then weld on additional armor to achieve an effective thickness of 7 ½ inches (190.5 mm). After this was incorporated into the tank, a tentative Ordnance Committee Minute (OCM) was written up on August 14th, 1944 for a total of 15 T1E1 tanks to be modified with the 5 remaining T1E1s being used for spare parts. This new vehicle was christened the M6A2E1 in the OCM, and delivery was projected for November 15th, 1944. The Army Ground Forces, who were encouraged by the idea of the tank and the project from the start, sent a cablegram to General Eisenhower on the matter on August 2nd, 1944. General Eisenhower’s reply on the 18th was that the M6A2E1 tanks were not wanted as they were deemed impractical for use. This effectively killed the project. This may not have been a bad thing, as tests with a T1E1 (M6A2) loaded to the expected weight of 77 tons (69.8 tonnes) showed poor climbing abilities, being unable to advance on a slope of more than 40 percent (22 degrees) inclination. Given there would not have been enough time to change the drive-gear reduction, the M6A2E1 would have been limited in what terrain it could operate on.
Following this cancellation, it was requested that two should still be finished in order to test the T29’s turret and armament. This request was granted and 3 turrets were built by the Continental Foundry & Machine Company. Two of these turrets were then mounted on modified M6A2’s and were tested at the Aberdeen Proving Ground, Maryland, with the third turret being sent for ballistic testing at Watertown Arsenal, Massachusetts. The plan for additional armor of the initial designs was never implemented.
M6A2E1-1 at Aberdeen Proving Grounds on June 7th, 1945 showing the later added muzzle brake. Photo: Hunnicutt’s Firepower
Despite the M6A2E1 being used as a test bed for the T29 turret, the turret design for the T29 had not been finalized and was constantly being changed, subjecting the M6A2E1 to turret modifications. The earliest of these modifications was a turret proposal dated around August 1944 calling for frontal turret armor up to 7.5 inches thick (190 mm) and a gun mounting with -10 degrees gun depression and +20 degrees elevation. In September that year, a decision was made to make three turrets for testing. Two of these were intended to be fitted onto tanks, and the third was for ballistic testing. The first mockup of this turret was seen around October. At this stage, the turret was essentially an enlarged Medium Tank T26 turret. In this initial design, much of the specifics were not fully detailed, such as where the commander would sit and if it would have one or two loaders. The front turret armor was also increased to 8 inches (203 mm) on a large external mantlet.
In December 1944, this design was further modified. The mount needed to be able to, at a minimum, provide -5 degrees of gun depression and +15 degrees elevation, and if possible -10/+20. The turret was to be traversed manually or through an electric turret drive, and no attempt was to be made at stabilizing the gun owing to limitations with the gun mount. In January 1945, a further rework was done, this time to facilitate the installation of a 155 mm gun. By February that year, a contract was placed for the production of these 2 turrets, in addition, the turret was redesigned further to be lighter and more practical. The gun was moved inwards slightly and switched to separate two-piece ammunition. In March, it was decided to increase the armor basis for the turret and gun shield.
The ammunition stowage, which was up to this point based mostly on the T26E1’s, was refined. The revised stowage now had capacity for 46 projectiles to be stored in the turret and a further 17 rounds stored in the hull, with 9 cartridge cases being carried in the turret for use as ready rack ammunition for a total of 72 rounds. In April 1945, a minor modification was done, assigning the commander a spot in the turret bulge on the center line. Due to the continual changes on the M6A2E1 and the parallel T29 project, in August, it was decided that these turrets were no longer deemed comparable to the current design for the T29’s turret and as such the M6A2E1s role of testing turret design was complete.
During these constant modifications, a side project was also started, which was primarily aimed at lightening the turret by reducing the armor thickness, although this was not applied to any the produced turrets. The intended armor for this was as of December 1944, 2.5 inches (63.5 mm) on the turret sides, 1.5 inches (38 mm) turret top, and a 3.5 inch (89 mm) gun shield.
The two produced tanks which were finished were not the same and were sub-designated M6A2E1-1 and M6A2E1-2. The M6A2E1-1 was similar to a typical M6, while the M6A2E1-2 was different, with its front plate being more vertically angled.
The M6A2E1-2 at Aberdeen Proving Grounds on October 3rd, 1945. This image shows the original gun configuration without a muzzle break. Photo: Aberdeen Proving Ground.
Armament and Fire Control
In addition to the constant turret development, the M6A2E1 was also a test bed for the T5 105 mm gun and its mounting equipment. The initial gun was based on the T4 105 mm AA gun, but had reduced barrel length and fired one piece ammunition. However, this ammunition was long and the gun would have needed to been depressed to allow loading.
The initial T5 gun, the barrel on this gun was also smaller at L48. Photo: Watervliet Arsenal
As a result, this was changed to the T5E1 gun firing two-piece ammunition. Additionally, it was decided to lengthen the barrel to the same length as the T4 105 mm AA gun. During trials, the tank fired T32E1 Armor Piercing Capped Ballistic Capped (APCBC), T29E3 High Velocity Armor Piercing (HVAP), T30E1 High Explosive (HE) and T46 White Phosphorus (WP). While these are the only known shells tested with the gun, it could have fired any round for the T5E1 105mm, such as T13 (APCBC), T37 Armor Piercing Ballistic Capped (APBC), and T182 (APBC). The tank also included a .30 caliber coaxial Browning machine gun for the gunner in the turret and on top there was a flexible AA mounting for a .50 caliber M2. For fire control, the M6A2E1 used the M70E2 sighting telescope. For indirect fire, either the M10 panoramic telescope or M62 elbow telescope would be used, and for vision, an M10 periscope was to be provided.
The commander and driver were the only people with any good vision of the outside, the gunner also had vision of the outside but this was limited to the tank’s gun optics.
Later T5E1 showing its longer L65 barrel. Photo: Watervliet Arsenal
The hulls of the M6A2E1’s were very similar to that of the normal M6 tank, however, a few modifications were made. The T29 turret was designed for an 80 inch (203cm) turret ring, whilst the M6 had been designed for a 69 inch (175cm) ring, so the turret ring had to be expanded.
Top-down view of the M6A2E1-1, looking at the hull and turret roof. Photo: tankarchives
This tank’s crew consisted of 5 men – 2 loaders, a gunner, a commander in the turret, and the driver in the hull.
The running gear consisted of Horizontal Volute Spring Suspension (HVSS) and utilized the T31 tracks, just like that on the standard M6 heavy tank.
Side profile shot of the M6A2E1-1 showing the running gear. Photo: tankarchives
The two M6A2E1’s assembled were sent to Aberdeen Proving Ground for testing. This testing was to compose of turret design and armament testing. An early fault found with the gun mounting was the use of bronze trunnion bushings. These were not strong enough and caused excessive trunnion friction with the gun and were quickly switched to needle bearings which reduced this friction to an acceptable amount. In a later firing test, during which some 119 rounds were fired, it was found that the hand wheel effort needed on the elevation mechanism gradually increased and eventually it required so much effort the firing was stopped and the unit taken apart to find the fault. Upon disassembly, it was revealed that the trunnion caps, due to a design fault, had been rubbing against a part of the firing mechanism causing increased friction during firing. While testing the gun mount and elevation systems, priority was given to strain readings on the elevation mechanism when the tank was driven cross-country. To this extent, the elevation mechanism was tested over 9 runs at 5 (8 km/h) to 10 mph (16 km/h) with the tank mounting a muzzle brake and counterweight. During this, the elevation mechanism failed during the second run at 10 mph (16 km/h) with the tension reading 105,000 lbs (47.6 tonnes).
M6A2E1-1 operating at the Churchville test course at Aberdeen Proving Grounds in July 1945 Photo: Hunnicutt’s Firepower
The tanks finished testing in 1946. Following this, the first M6A2E1-1 was displayed at Aberdeen Proving Grounds, however, in the 1950s, this tank, along with various other vehicles at Aberdeen, was sent for scrapping. The history of the second M6A2E1 produced is unknown, but if it was not scrapped at the conclusion of its testing, it was likely scrapped along with the first one later on.
While its design was rejected for use in combat, it was still important to the development of the T29 tank. Due to the use of existing unused T1E1s for a hull, they were able to have a tank ready that could test design choices for the upcoming T29 tank. When the tank was finished with turret design, it would find usage testing out the T5 105mm gun as well as gun mounting aspects with lessons learned from this being implemented in the T29 program.
11.18 x 3.12 x 3.48 m (36’8’’ x 10’3’’ x 11’5’’ ft)
Total weight, battle ready
69.85 tons (70.8 tonnes)
5 (Driver, commander, gunner, 2 loaders)
Wright G-200 9 cylinder 960 hp@2300 rpm
18 mph (29 km/h) on road
100 miles (160 km) on road
Main: 105 mm Gun T5E1
Sec: Browning M2HB .50 Cal (12.7mm) machine gun, .30 Cal (7.62mm) Browning M1919 machine gun
1.75 inches (44 mm) to 9 inches (228 mm)
R.P. Hunnicutt, Firepower: A History of the American Heavy Tank, Presidio Press
R.A.C Technical Situational Reports No 26, 27, 29, 30, 31, 32, 34, 35, 36, 37, 38
Aberdeen Proving Ground Photograph
Metallurgical Examination of Sections from the Cast Armor Turret made by Continental Foundry and Machine Company and two Trunnion Pins from a Heavy Tank M6A2E1 Watertown Arsenal ADA954836
Watervliet Arsenal Photographs
History of the Heavy Tank M6A2E1
Development History of the Heavy Tanks, T29 & T30 tankarchives.blogspot.com
Illustration of the Heavy Tank M6A2E1-1, produced by Tank Encyclopedia’s own David Bocquelet.
At the time of its conception, the Canal Defence Light, or CDL, was a Top Secret project. This ‘Secret Weapon’ was based around the use of a powerful Carbon-Arc lamp and would be used to illuminate enemy positions in night attacks as well as disorient the enemy troops.
A number of vehicles were converted to CDLs, such as the Matilda II, the Churchill, and the M3 Lee. In keeping with the highly secret nature of the project, Americans designated vehicles carrying the CDL as “T10 Shop Tractors.” In fact, the designation “Canal Defence Light” was intended as a code name to draw as little attention to the project as possible.
Looking at the CDL tanks, one would be forgiven for thinking that they were one of the famous ‘Hobart’s Funnies.’ but in fact, the man credited with the creation of the Canal Defence Light was Albert Victor Marcel Mitzakis. Mitzakis designed the contraption with Oscar De Thoren, a naval commander who, like Mitzakis, had served in the First World War. De Thoren had long championed the idea of armored searchlights for use in night attacks and the project continued under the supervision of the venerable British Major General, J. F. C. “Boney” Fuller. Fuller was a noted Military historian and strategist, credited as one the earliest theorists of modern armored warfare. With Major General Fuller’s backing, and even the financial support of the Second Duke of Westminster, Hugh Grosvenor, the first CDL prototype was demonstrated to the French Military in 1934. The French were not keen, thinking the system was too fragile.
The British War Office had refused to test the device until January 1937 when Fuller contacted Cyril Deverell, the newly appointed Chief of the Imperial General Staff (C.I.G.S.). Three systems were demonstrated on Salisbury Plain in January and February 1937. Following the demonstration which took place on Salisbury Plain, three more of the devices were ordered for tests. There were delays, however, and the War Office took over the project in 1940. Tests finally began and orders were placed for 300 devices that could be mounted to tanks. A prototype was soon constructed using a spare Matilda II hull. A number of Churchills and even Valentines were also supplied for the tests.
The turrets were manufactured at the Vulcan Foundry Locomotive Works in Newton-le-Willows, Lancashire. Components were also produced at the Southern Railway workshops in Ashford, Kent. The Ministry of Supply delivered the Matilda hulls. The turrets were identified by Type, eg. Type A, B & C. The Ministry of Supply also established an assembly and training site known as the CDL School at Lowther Castle, near Penrith, Cumbria.
The CDL was demonstrated to United States officials in 1942. Generals Eisenhower and Clark were present for the demonstrations. The American’s became intrigued by the CDL, and decided to develop their own version of the device. Designers chose the then outdated and plentiful M3 Lee Medium tank as a mount for the light.
For the purposes of extreme secrecy, production stages were split between three locations. The Arc-Lamps being provided by the US Army Corps of Engineers, the American Locomotive Company, New York, worked on modifying the M3 Lee to accept the CDL turret and the Pressed Steel Car Company, New Jersey, constructed the turret as “Coastal Defence Turrets.” Finally, the components were united at the Rock Island Arsenal, Illinois. 497 Canal Defence Light equipped tanks had been produced by 1944.
Crews were trained at Fort Knox, Kentucky, and in the huge Arizona/California maneuver area. Crews training with the vehicles – codename “Leaflet – went under the codename “Cassock.” Six Battalions were formed and would later join British CDL tank regiments, covertly stationed in Wales.
American crews came to call the CDL Tanks “Gizmos”. Tests would later begin to mount the CDL on the newer M4 Sherman chassis, developing their own unique turret for it, which will be explored in a subsequent section.
Let There Be Light
The Carbon-Arc searchlight would produce a light as bright as 13 Million candle-power (12.8 million candela). Arc-Lamps produce light via an arc of electricity suspended in air between two carbon electrodes. To ignite the lamp, the rods are touched together, forming an arc, and then slowly drawn apart, maintaining an arc. The carbon in the rods vaporizes, and the vapor produced is extremely luminous, which produces the bright light. This light is then focussed by a large concave mirror.
Using a series of mirrors to reflect it, the intensely bright beam of light passes through a very small vertical slit on the left of the turret face. The slit was 24 inches (61cm) tall, and 2 inches (5.1cm) wide and had a built in shutter that would open and close two times per second, giving the light a flickering effect. The theory was that this would dazzle enemy troops, but also had the added bonus of protecting the lamp from small-arms fire. Another tool to dazzle troops was the ability to attach an amber or blue filter to the lamp. Coupled with the flashing, this would increase the dazzling effect and could still illuminate targets areas effectively. The system also allows for the use of an infra-red illumination bulb so that IR vision systems can see at night. The field covered by the beam was a 34 x 340 yards (31 x 311 m) area at a range of 1000 yards (910 m). The lamp could also elevate and depress 10 degrees.
“…a source of light placed at the focus of a parabolic-elliptical mirror reflector [made from aluminium] is thrown by this reflector near the back of the turret which directs the directs the beam forwardly again to focus at or about an aperture in the wall of the turret through which the light beam is to be projected…”
An excerpt from Mitzakis’ patent application.
The device was housed in a special one-man cylindrical turret that was squared off on the left, and rounded on the right. The turret could not rotate 360 degrees as the cabling would snag so could only rotate 180 degrees left or 180 degrees right but not all the way around. The turret featured 65 mm of armor (2.5 in). The operator inside, listed in the vehicle design as “observer”, was positioned on the left side of the turret, partitioned off from the lamp system. The commander was issued with a pair of Asbestos gloves which were used when the carbon electrodes that power the light burned out and needed changing. He also had the role of operation the tank’s only weapon, a BESA 7.92 mm (0.31 in) machine gun, which was positioned on the left of the beam slit in a ball mount. The device was also designed to be employed on small naval vessels.
The faithful “Queen of the Desert,” the Matilda II, was now a largely considered outdated and outclassed in the European theatre, and as such there was a surplus of these vehicles. The Matilda II was the first tank to be equipped with the CDL Arc-Lamp turret, identified as the Type B turret. The Matildas were as reliable as ever with reasonable armor, however they were still extremely slow, especially compared to the more modern tanks entering service. As such, the Matilda hull gave way to that of the M3 Grant, which could at least keep up with the majority of Allied vehicles as well as sharing a lot of component parts with other Allied vehicles, making supply easier.
Another variant of the Matilda came out of this project, the Matilda Crane. This involved a Matilda using a specially designed crane attachment, that could lift off the CDL or standard turret as required. This allowed an easy conversion, meaning that the subject Matilda could be used as a gun tank, or a CDL tank.
The Churchill is the rarest of the CDLs, with no pictorial records whatsoever, barring a cartoon from a newspaper. The 35th Tank Brigade, as well as being issued with Matildas, were also issued with Churchills, forming the 152nd Royal Armored Corps. It is unclear whether these Churchills were ever equipped with the CDL. The turret ring for the Churchill was only 52″ (1321mm) compared to 54″ (1373mm) on the Matilda and the later M3 Grant. The turrets, therefore, were not interchangeable from Matilda or M3 CDLs. Armor on the turret was also increased to 85mm.
There is a written record for the existence of the Churchill CDL in the form of a report by a member of the 86th Field Regiment, Royal Artillery, stating that he witnessed Churchills equipped with CDLs deployed on the 9th February 1945 near Kranenburg, Germany.
An excerpt from his report: “A Churchill tank carrying a searchlight took up position at the rear of our position and at night floodlit the area, pointing its beam over the town. They turned night into day and our gunners working on the guns were silhouetted against the night sky.”
In the long run, the M3 Grant was always the intended mount for the Canal Defence Light. It was quicker, able to keep up with its compatriots, and retained its 75mm tank gun allowing it to defend itself much more effectively. Like the Matilda, the M3 Grant was largely considered obsolete, so there was quite a surplus of the tanks.
The CDL replaced the secondary armament turret atop the M3. The M3s, originally, were also fitted with the Type B turret of the Matilda. Later, the turret was changed to the Type D. This welded up some of the ports and openings, but also saw the addition of a dummy gun next to the beam slit to give it the appearance of a normal gun tank. The Americans also tested the M3, known as the Lee in their service, as a CDL tank. The tanks used were mostly of the M3A1 type with the cast super-structure. The turret was mostly identical to the British pattern, the major differences being a ball mount for a Browning M1919 .30 Cal. as opposed to the British BESA.
After the M3 CDL, the M4A1 Sherman was the next logical choice for a variant. The turret used for the M4 was much different than the British original, designated the Type E. It consisted of a large round cylinder, that featured two shuttered slits in the front, for two Arc-Lamps. The lamps were powered by a 20-kilowatt generator, driven by a power takeoff from the tank’s engine. The commander/operator sat in the middle of the lamps, in a central sectioned off compartment. In the middle of the two beam slits, there was a ball mount for a Browning M1919 .30 Cal. machine gun. There was a hatch in the middle of the turret roof for the commander. A few were also trialed using the M4A4 (Sherman V) hull. The use of the M4 did not get past prototype stages, however.
The Prototype M4 CDL
Matilda CDL of the 49th RTR – 35th Tank Brigade, north-eastern France, September 1944. Churchill CDL, western Rhine bank, December 1944.
M3 Lee/Grant CDL, other wise known as a “Gizmo”. Medium Tank M4A1 CDL prototype. All illustrations are by Tank Encyclopedia’s own David Bocquelet
As it would happen, the Canal Defence Lights saw extremely limited action and did not operate in their intended roles. Due to the secret nature of the CDL project, very few armored commanders were actually aware of its existence. As such, they were often forgotten and not drawn into strategic plans. The operational plan for the CDLs was that the tanks would line up 100 yards apart, crossing their beams at 300 yards (274.3 meters). This would create triangles of darkness for attacking troops to move forward in while illuminating and blinding enemy positions.
The first CDL equipped unit was the 11th Royal Tank Regiment, formed early in 1941. The regiment was based at Brougham Hall, Cumberland. They trained at Lowther Castle near Penrith at the specially established ‘CDL School’, set up by the Ministry of Supply. The Regiment was supplied with both Matilda and Churchill hulls, with a total of 300 vehicles. British CDL equipped units stationed in the United Kingdom could later be found as part of the British 79th Armored Division and 35th Tank Brigade, they were joined by the American 9th Armored Group. This group trained in their M3 CDLs at Camp Bouse, Arizona, before being stationed in the United Kingdom. They were then stationed in Wales, in the Preseli Hills of Pembrokeshire where they would also train.
A Grant CDL testing its beam at Lowther Castle
In June 1942, the battalion left the UK, bound for Egypt. Equipped with 58 CDLs, they came under the command of the 1st Tank Brigade. The 11th RTR set up their own ‘CDL School’ here, where they trained the 42nd Battalion from December 1942 to January 1943. In 1943, Major E.R. Hunt of the 49th RTR was detailed in late 1943 to lay on a special demonstration for the Prime Minister and op Generals. Major Hunt recalled the following experience:
“I was detailed to lay on a special demonstration with 6 CDL tanks for him (Churchill). A stand was erected on a bleak hillside in the training area at Penrith and in due course, the great man arrived accompanied by others. I controlled the various maneuvers of the tanks by wireless from the stands, ending the demo with the CDLs advancing towards the spectators with their lights on halting just 50 yards in front of them. The lights were switched off and I awaited further instructions. After a brief interval, the Brigadier (Lipscomb of the 35th Tank Brigade) rushed up to me and ordered me to switch on the lights as Mr. Churchill was just leaving. I immediately ordered the 6 CDL tanks to switch on: 6 beams each of 13 million candlepower came on to illuminate the great man quietly relieving himself against a bush! I immediately had the lights extinguished!”
Back in the UK at Lowther, two more tank battalions had converted to CDL units. These were the 49th Battalion, RTR, and 155th Battalion, Royal Armoured Corps, and were equipped with Matilda CDLs. The third battalion to arrive was the 152nd Regiment, RAC, who were equipped with Churchill CDLs. The 79th Armored Division was the first Canal Defence Light force to see deployment in Europe in August 1944, the other units were retained in the UK. Rather than let the remaining crews sit idle, they were assigned to other roles, such as mine clearance or assigned to regular tank units.
In November 1944, Canal Defense Lights of the 357th Searchlight Battery, Royal Artillery provided light for the mine-clearing flail tanks clearing a path for Allied armor and infantry during in Operation Clipper. This was one of the CDLs first uses in the field.
An M3 CDl on the Bank of the Rhine, 1945. The device is concealed under a tarp. Photo: Panzerserra Bunker
The Canal Defence Lights only real action, however, was at the hands of United States forces during the Battle of Remagen, specifically at the Ludendorff Bridge where they assisted in its defense after the Allies captured it. The CDLs were 13 M3 “Gizmos,”, from the 738th Tank Battalion. The tanks were perfect for the task, as they were sufficiently armored to stand up to the defensive fire coming for the German controlled East Bank of the Rhine. Standard searchlights would have been destroyed in seconds but the CDLs were successfully used to illuminate every angle to deter surprise attacks. This included being shone into the Rhine itself (fitting the vehicle’s name), which helped reveal German frogmen trying to sabotage the bridge. After the action, without the need to defend against incoming fire, captured German spotlights took over the role.
After the action, a captured German officer reported in questioning: “We wondered what those lights were as we got the hell shot out of us as we tried to destroy the bridge…”
British M3 Grant CDLs were used as their forces crossed the Rhine at Rees. The CDLs drew heavy fire with one of the tanks being knocked out. More were used to cover British and US forces as they crossed the Elbe River Laurenburg and Bleckede.
Some Canal Defence Lights were ordered for the Pacific Campaign in 1945 by the US 10th Army for the attack on Okinawa, but the invasion was over by the time the vehicles arrived. Some British M3 CDLs did make it to India under the 43rd RTR and were stationed here for the planned invasion of Malaya in February 1946, the war with Japan came to an end before this of course. The CDLs did see a form of action however, by assisting the Calcutta Police in the riots of 1946 with great success.
To no surprise, CDL survivors are rare today. There are only two on public display in the world. A Matilda CDL can be found in The Tank Museum, Bovington, England and an M3 Grant CDL can be found at the Cavalry Tank Museum, Ahmednagar in India.
The Matilda CDL as it sits today in The Tank Museum, Bovington, England. Photo: Author’s Photo
The surviving M3 Grant CDL at the Cavalary Tank Museum, Ahmednagar, India.
An article by Mark Nash with research assistance from Andrew Hills
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.
One of the only two running Jumbos, restored by Jacques Littlefield and now operated by the Collings Foundation – Source: Auctions America
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 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.
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.
Xmas special 2019 David B. Poster: Support Tank Encyclopedia and get the most accurate depiction of M4A3E2 Cobra King “First in Bastogne”. See below for the complete history
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.
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 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 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. 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. 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.
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 “Jumbo” from the 33rd Battalion, 3rd US Armored Division, Houffalize, Belgium, January 1945. M4A3E2 Jumbo “Cobra King” with the “First in Bastogne” inscription, probably the most famous Jumbo of the entire 4th Armored Division.
M4A3E2(76) Jumbo from the 37th Tank Battalion, 4th Armored Division, Alez, Germany, March 1945.
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.
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
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
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
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
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 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
The Disston Tractor Tank (sometimes known as the Disston 6-ton Tractor Tank) was essentially a Caterpillar tractor that was given a simplistic armored superstructure, a turret, and a modest armament of a .30 cal (7.62 mm) machine gun and 37 mm (1.46 in) cannon. It was a Great Depression-era business venture – The idea being to sell cheap tanks to the military, knowing full well that value for money would be a key selling point during the period. However, they were, for the most part, deemed unsatisfactory, and eventually ended up being marketed to developing nations such as Kuwait, Romania, and Afghanistan for army / policing use.
The vehicle is very obscure and a lot of its history remains a mystery. Only Afghanistan is a confirmed user of the Disston Tractor Tank, with an estimated five surviving in scrapyards to this day. There are also claims of attempts to sell the vehicle to China, Canada, New Zealand, and even the USMC, which will be evaluated in this article.
Four Disston Tractor Tanks in Afghanistan, circa late 30s. One source has suggested that these tanks may have just arrived in Kabul, hence their armaments being removed. However, the original caption does not suggest this to be the case. A driver can just about be made out inside the vehicle on the left side – the driver’s armored port has been lowered down (see other photos for a comparison). Also, there appears to be a tiny hatch just next to the engine deck, with an unknown purpose – possibly maintenance. As taken from an unknown German book on Afghanistan from 1940.
The Disston Tractor Tank was a risky business venture with the aim of selling cheap but effective weapons to the military during the Great Depression. According to “Mobilize!: Why Canada Was Unprepared for the Second World War” by Larry D. Rose, they only cost $21,000 ($366,750 in today’s money), which might sound like a lot, but it was roughly half the price of a contemporary British light tank, and with their 37 mm armaments, they were hardly under-armed vehicles for a mere tractor tank.
The exact creator and designer of the vehicle is the subject of debate – sources will either cite the Disston Company or the Caterpillar Tractor Company. There is strong evidence for both. For example, the Disston Company had helped Frank Sutton with his very similar design, the Sutton Skunk , and what’s more, they seemed to have done all the assembly of the vehicles.
However, it seems more likely that the idea came from Caterpillar – according to “A Place to Live and Work: The Henry Disston Saw Works and the Tacony” by Harry C. Silcox. At some point in the “mid-1930s“, William D. Disston was asked by Caterpillar Tractor Company of Peoria to create tank armor sets for tractors – which implies that Caterpillar at least came up with the concept, if not the exact design. Disston received Caterpillar Model 35 (not, as some sources suggest, Model 30) tractors and assembled them into tanks. Assuming that this is true, the name “Disston” was likely used for the tractor tanks because either the Disston name had significant brand power (which it indeed did), or because Disston came up with the exact design. At some point, Otto Kafka Incorporated was involved in this deal, most likely purely for marketing, but it is unclear how they came to be involved.
One of the big unknowns of the Disston tractor tank project is when the idea was conceived. Evidence suggests that the idea came about in 1933, as there was an attempt to sell some to Kuwait in January 1934. Included in a pair of letters to Kuwait from Otto Kafka Incorporated is a leaflet advertising the Disston Tractor Tank, which includes a photo of a Disston tractor tank prototype. Logically, it follows that the agreement between Caterpillar and Disston took place in 1933 (or perhaps, but not likely, January 1934), with one prototype made at that point.
The Disston Tractor Tank was, essentially, a boxy, armored body placed onto a Caterpillar Model 35 tractor. The armor appears to have been totally riveted together, with an entry door at the rear. The turret seems to have an access hatch. An engine access hatch also appears to be placed on either side of the engine deck. There were three types of Disston Tractor Tanks – 1. Prototype. According to esotericarmor.blogspot, this vehicle is a simplified ‘late type’, but this does not appear to be the case. This type has only been seen on advertising leaflets with a 37 mm gun mounted with a gunshield instead of a turret. Its hull shape is simpler than other types. It features a short track assembly / suspension which is the original Caterpillar Model 35 design. It also has a large grill at the front of the vehicle for air intake. It is believed to be the prototype as a 1935 advertising leaflet suggests “scrap metal was used to armor the original model“, with a picture of this type below. According to the leaflet, it only took two hours to assemble the prototype – not to convert the tanks back into tractors, as some sources have suggested. 2. Main type – Longer track assemblies. This is the most common type, of which four are known to have been made, albeit with slightly varying hull dimensions. The longer track assembly appears to have been modestly made – a third roadwheel has been added in front of the larger, original front wheel. It is held in place by a large metal bar, riveted to the rest of the assembly. The rest of the track assembly appears unchanged. There are plenty of maintenance hatches on the vehicle – one either side of the engine deck, and perhaps another two in front of the driver’s and secondary gunner’s positions. There seems to be some small, near unnoticeable differences between individual hulls, such as the height of the engine deck (see photos). These vehicles were likely upgraded with engine ventilation grills at some point after the late 30s. 3. Short track assembly – in Afghanistan, a standard body type has been seen mounted on an unaltered tractor chassis. The reason why this type was made is unclear. It is most likely that this is simply how the vehicle was built and delivered from Disston. However, it could possibly be the prototype upgraded with a new body type. It could also possibly be a local conversion of the same Caterpillar tractor – according to one source, Afghanistan ordered extra armor shells without tractors (although whether this is true or not is still in debate), so it is possible that it was an Afghan conversion, but this is unlikely. Strangely, the hull of the vehicle also does not appear to be as long as the others.
Every Disston Tractor Tank featured two guns – a 37 mm M1916 gun in the turret (although the vast majority of photos show no gun barrel), and a .30cal machine gun in the hull (probably a Marlin, as these were commercially available), with perhaps five other gun ports (two on either side of the hull, and one on the rear, although it is unclear which are viewports, and which are gun ports). Armor thickness is unknown. One source suggests 6-13 mm (0.24-0.51 in), but another source suggests 6-8 mm (0.24-0.31 in). In any case, the armor would certainly stop small arms fire and light shrapnel.
Its speed is estimated to be roughly 5-6.5 mph (8-10.5 km/h) with a 47.5 hp, 4 cylinder, diesel engine. In the lower front plate covering the engine, a small hole is visible, which is for inserting a rod to start the engine. It is unclear where the exhaust pipe had been moved to.
The crew consisted of three – a driver, commander/main gunner, and a secondary gunner. However, according to advertisements, the tank also had troop transport capabilities, with a maximum of seven men.
Once it was realized that western buyers such as the US military were, for the most part, not interested, the tanks were instead marketed to developing nations such as Kuwait and Afghanistan. This process began as early as 1934, with the first known attempt in January 1934, to Kuwait. The design was well-marketed, with letters addressed to foreign leaders with informative pamphlets enclosed. The only nations it was known to be marketed to are Kuwait, Afghanistan, Romania, and possibly Canada. It is highly likely that attempts to sell to other nations happened between 1934 and 1935 via Otto Kafka Incorporated, but these documents may remain hidden in national archives.
Kuwait seems to have been the first known to receive a sales pitch involving the Disston Tractor Tank. At some point, Otto Kafka Incorporated was involved in the Disston Tractor Tank deal with Caterpillar and Disston, possibly a result of companies collaborating in order to survive the Great Depression, or perhaps a desperate attempt to make money on the near-failed tractor tank project.
Two letters dated January 23rd, 1934 were sent to Sheikh Ahmad Al Jaber Al Sabah, the ruler of Kuwait (although addressed to the Minister of War, Kuwait had no equivalent, so they were delivered to the Sheikh) from Otto Kafka, who was the president of Otto Kafka Incorporated (New York). The first outlined the military application of “Disston Impenetra Steel”, and the second discussed the Disston Tractor Tank. The second letter states:
“What the auxiliary cruiser is to a Navy, the Disston Tractor Tank is to an Army or Police Force. Both are useful and useable in peace and war. They both pay their way. The Disston Tractor Tank is the latest in army and police equipment. It is, in fact, a combination war and peace machine, and it has created a sensation in military and police circles. Your excellence, we trust, will appreciate its many advantages of which a few are summarized as follows: 1. The price of the Disston Tractor Tank is less than one half of the usual war tank. 2. Being smaller it is more ambulant and, therefore, it can be used to advantage in city streets and in difficult war terrain. 3. It is equipped to be a highly efficient combat and troop transport machine. It is an efficient offensive weapon for use against the enemy across the border, or for use to quell riots, to dispel mobs in case of civil disturbances. 4. The armature with its equipment of a 37mm. gun in the back, a machine gun in the front, and toxic gas equipment can be attached with a few moments’ work at any well-equipped garage, converting the war tank into a serviceable tractor for agricultural purposes, for general hauling and for the many other uses of the ordinary tractor. 5. The Disston Tractor-Tank accommodates a crew of three in combat, or seven when used for transportation of troops. Will it please Your Excellency to consider Disston Tractor Tanks as your standard military, navy and police equipment. We will be glad to supply more detailed information upon request.”
No orders were placed, but it caught the attention of Harold Dickinson, a British political agent in Kuwait. In a letter dated 15th February 1934, addressed to Lieutenant Colonel T.C. Fowle, Dickinson suggests that Fowle intended to report the attempted sale to the British government. He also remarks that the attempted sale was “not a very edifying procedure when their Government (the U.S.A) is supposed to be taking the leading part in the world today to try and stop war etc“.
Unfortunately, no further details are available on this incident.
According to “The Romanian Army and the Evolution of the Tank branch. Documents. 1919-1945” by Commander Doctor Marian Moşneagu, Doctor Iulian-Stelian Boţoghină, Professor Mariana-Daniela Manolescu, Doctor Leontin-Vasile Stoica, and Professor Mihai-Cosmin Şoitariu, there was an attempt by Otto Kafka to sell Disstons to Romania. In the mid-1930s, Romania was attempting to acquire foreign tanks in order to develop their armored corps.
By 24th July, 1935, B.D. Zissu informed Romanian army leaders that Kafka was “in a position to supply to Romania the latest type of tanks at advantageous prices and payment conditions“. Zissu recalled that it would be possible to quickly replace damaged parts (as Caterpillar had branches across the world) and that the vehicle would be compact, cheap, have solid construction, could use a variety of fuels (apparently including alcohol), and, it had the possibility to be reconverted into an agricultural tractor.
The Ministry of Defense sent an invitation on 20th August 1935, for the Disston to take part in a tank competition in September. Kafka refused, stating that the Romanians had to buy the vehicles first – perhaps suggesting something about the manufacturer’s opinion of the vehicle. Romanian officials refused this condition.
On 12th November, B.D. Zissu represented a new offer to Romanian officials, whereby they would travel to the USA to view the vehicles, all travel expenses paid, on the condition that twenty-five vehicles would be bought. Again, this proposal was refused, mainly due to the high transport costs and unlikeliness of obtaining spare parts during wartime conditions.
Afghanistan is the only confirmed operator of the Disston, but their order has also been the subject of the debate in terms of when it was placed, and what the exact order was.
Silcox suggests it was nine tanks and three extra armor sets, but gives no date as to when the order was placed. However, in “US Military Tracked Vehicles” by Fred W. Crimson, it is suggested that ten were ordered. In “Tanks of the World 1915-45” by Peter Chamberlain and Chris Ellis, it is suggested that three were delivered.
Despite these claims, it is the author’s belief that only five tanks (and nothing more) were sent to Afghanistan, one of which was a short track assembly type, because photographic evidence, both from the late 1930s, and modern photos of Disston wrecks show five and nothing more.
In any case, the order was reportedly shipped in 1935 to Karachi, India (now Pakistan), and sent via train to Kabul, Afghanistan. A holiday was supposedly declared, and the tanks were paraded in the city square. It is unknown how long these vehicles were in service for, although they appear to have been used at least until after WWII. It seems as though they were, at some point (believed to be after 1937), fitted with a pair of grills at the front of the engine compartment (cut into the original armor plate), probably to avoid engine overheating. Their operational colors are unclear – most modern photos show them to be sand yellow, but one in the National Museum of Afghanistan (in Kabul) was painted dark green with an Afghan roundel. Strangely, the same tank is believed to have been seen in a scrapyard in sand yellow livery.
There are no further details of their use in Afghanistan. Surviving Vehicles in Afghanistan
The earliest reported sighting of a Disston by a US soldier was perhaps as early as 2003. Since then, a common figure for the current number of Disstons remaining is two or three, but this does not appear to be the case – it seems that all five Afghan Disstons have been accounted for by modern photographs.
Reports from soldiers in Afghanistan is the best source to find out where these vehicles now lie, but reports from soldiers and photographs do not match up. Kingston Montgomery Winget (who was in Afghanistan in 2015) has said that he has seen three. Ian Parker (who was in Afghanistan in 2015) has reported only seen two (but believes that there are three in Afghanistan). Testofbattle.com forum user “cmikucki” (who was in Afghanistan circa 2006) has only reported seeing one at KMTC (but has reported seeing another near Darul Aman Garrison, and also believes there to be a third Disston somewhere else). Other soldiers, namely, Dean Larsen, who served in Kanadahar in 2007, and Steve Tyliszczak, who served primarily in Regional Command East, are helpful with their information on vehicles being scrapped in Afghanistan.
The varying figures are fairly simple to explain – not looking for Disstons specifically might seem obvious, but it must be noted that according to Dean Larsen, Soviet vehicles had been cut up by locals and parts were likely re-purposed. Worse still, a modern LAV III was abandoned overnight, and once the crew returned to recover it the following morning, all the tires were gone, and someone was even stripping down the armor plates! Similarly, Steve Tyliszczak recalls that small tank graveyards have been consolidated into larger graveyards, and the Chinese have been cutting up vehicles for scrap in several different provinces.
Based on this information, it is quite likely that local salvagers (or more likely, military clean-up and scrap operations) have meant that the vehicles have been moved, damaged further (thus making the same vehicle in different photos hard to identify), or scrapped entirely.
However, based on the reports of the aforementioned soldiers and photographs, the author has pieced together a likely set of locations for the remaining Disston Tractor Tanks: One vehicle likely located near Darul Aman Garrison, south of Kabul, last seen 2006
A Disston was reported at Darul Aman Garrison in 2006, by testofbattle.com forums user “cmikucki“. “cmikucki“, who was in Afghanistan circa 2006, claims that he has seen only two Disstons. One at Pol-e-Charkhi, and another at Darul Aman Garrison. He believes that the one he saw at Darul Aman garrison still had its suspension and gun intact, and therefore, is the famous one from the National Museum of Afghanistan. This vehicle was kept outdoors, but the museum closed in the early 1990s when rival Taliban factions fought for control of Darul Aman palace (located over the road from the museum), and it was looted many times. It is probable that the Disston at the museum has been removed by looters and was probably abandoned nearby.
“cmikucki” believes this Disston to be a third, distinct from the ones that he has seen, because the one he saw at Darul Aman had its suspension intact. However, it is the author’s belief that this Disston is the one from the National Museum of Afghanistan, as no others are known to have been given a long replica gun.
There could be a number of reasons why “cmikucki” is wrong:
It is quite possible that he is simply mistaken, and has forgotten what he has seen. “cmikucki” has not described the gun barrel of either tank that he has seen, and it is plausible that he is mistaken for what a Disston’s gun barrel looks like.
It is also possible that the vehicle has had its suspension removed at some point between him seeing it, and it being photographed, hence why he does not recognize it and believes it to be distinct from the one he saw at Darul Aman. Based on information from Steve Tyliszczak and Dean Larsen about vehicle clean-ups, salvaging, and scrapping, this seems rather likely.
Up to four vehicles located inside Kabul Military Training Center, Pol-e-Charkhi, photographed and reported between 2006 and 2011
It is the author’s belief that there are perhaps as many as four at KMTC (up to three in one area, and one in another) because of photographic evidence, but several US soldiers have given different figures, which will be explored. Three Disstons can be seen together in 2006 – apparently all long track types (although it is hard to tell with the vehicle on the far left). According to the poster on g503.com forums, this photo was taken by French soldier circa 2006 at a “sideline Blackwater Base in Kabul“. This “sideline base” is almost certainly referring to Pol-e-Charkhi, and the mountainous terrain as seen in the background points towards this being the case, too.
According to sources, this photo was most likely taken between Forward Operating Base Scorpion and the Armor Branch School on the north-west side of Gharib Ghar, close to Range One and Two, and some old, bombed-out buildings. These vehicles appear to have been moved around over time, and may now be slightly further apart than the photo shows for aforementioned reasons.
The fourth Disston at Pol-e-Charkhi is believed to be in a different tank graveyard area, and is most likely the only short-track type in existence. According to Kingston Montgomery Winget, a single Disston is likely located at the fence line east of the Armor Branch School with many old Soviet vehicles, just before the firing ranges. This particular vehicle is believed by the author to be the ‘short-track type’, of which there are several photographs showing it alone. This is also most likely the vehicle that “cmikucki” reports seeing in 2006 at KMTC.
This is evidenced further by Charles Lemons (ex-curator of the US Armor and Cavalry Museum) as he suggests that this short track vehicle was last photographed circa 2011. Lemons has also provided photos of this skeletal Disston tank, which he suggests were taken at KMTC. This ‘skeletal Disston’ appears to be the vehicle on the far right (or possibly the center) of this grouping of three, which is believed to be between Forward Operating Base Scorpion and the Armor Branch School. Assuming this to be true, (as it is hard to tell, but it appears to be a long-track type), then this short track type is a fourth vehicle at Pol-e-Charkhi, and is, as Winget suggests, located at the fence line east of the Armor Branch School. Final note on likelihood of locations
However, due to the lack of photographs, the fact that available photos were taken over five years, the likelihood of further damage to the vehicles from scrapping (thus making it exceptionally difficult to identify individual vehicles), and the fact that some may have been moved around over time, it is near impossible to say where these vehicles are currently, what condition they are in, and how many vehicles are actually left. Possible Salvage
According to Ian Parker, the US Armor and Cavalry Museum contacted him in 2015 about arranging an export of at least one Disston. The ANA (Afghan National Army) would not even begin to entertain the offer without substantial bribes at multiple levels. He reports that he was offered a T-27, but in his opinion, getting it out through Pakistan would have been more trouble than it would have been worth.
Other potential users
The attempt to sell Kuwait and Romania Disston Tractor Tanks, and the successful sale to Afghanistan is documented with primary sources and clear photographic evidence. However, there were three more reported attempts to sell the vehicle. These are: the US Military (namely the US Army and US Marine Corps), Canada, New Zealand, and China. There is a general lack of credible evidence for each of these potential users/buyers, but the claims cannot be categorically dismissed either. In some cases, there has been difficulty obtaining the original source material for the claims, however, additional research on the claim has been undertaken in each case.
Sources will suggest that at some point between 1933 and 1935, the US Army was offered the tanks, but refused to buy any. In the same time frame, the USMC was reportedly interested and briefly operated sixteen. One source suggests that these tanks were from a diverted order from the Chinese, but this is not a substantiated claim. There is no photographic evidence for any of these suggestions, nor are there any available primary sources. Having contacted the US Army Center of Military History, and US Army Tank-automotive and Armaments Command (TACOM) for more information, both stated that they have no records of the Disston Tractor Tank.
Charles Lemons has stated that there is no photographic evidence for the Disston ever being in US military service. He suggests that the USMC would certainly have taken photographs if they ever did operate any. The USMC was still using the 6-ton M1917 (US license built Renault FT) into the late 1920s, after which the tank companies were disbanded. Interest in USMC tank units awakened again in 1936 and the Corps was interested in Marmon-Herringtons.
It is his opinion that the Disston would not have been a good choice for the Marines because of its weight and size, and therefore, none were bought by the USMC.
According to “The Great Tank Scandal, The Universal Tank” by David Fletcher, there were suggestions to mechanize the New Zealand Army with the Disston Tractor Tank. This claim’s original source is a paper written in 1938, although the exact paper is not source cited by Fletcher and cannot be traced further.
The later Bob Semple tractor tank from 1942 was a very similar design because it was built using a postcard depicting a Disston Tractor Tank. The Bob Semple was based on the similar Caterpillar RD8 (from 1939), featured suspension that was lengthened in nearly the exact same manner, a similar turret design, same hatch designs, and even featured the exact same pistol port design.
According to “Mobilize!: Why Canada Was Unprepared for the Second World War” by Larry D. Rose, in spring, 1935, the General Supply Company of Canada wrote to the National Defense Headquarters offering to produce the tanks for Canada. The proposal was rejected because the tanks were simply too slow. The source for this claim is cited, but unfortunately, obtaining a print copy of this book has proven difficult for the author, and therefore, the original source on Rose’s information about the Disston has not been evaluated.
Regardless, there are no other sources to substantiate this claim, and the National Defense Headquarters and The Library and Archives Canada have both stated that they have no documents relating to this subject.
China is reported to have received (or at least ordered) four tanks. No dates are given by sources for the order date, but according to “A Place to Live and Work: The Henry Disston Saw Works and the Tacony” by Harry C. Silcox, four tanks were built in 1938 and delivered in 1939 because of security concerns. The source for this claim is cited in the book, but due to an issue with obtaining a print copy of Silcox’s book, the source cannot be ascertained at this moment in time. Many other book sources also suggest that China received some tanks, too.
In contradiction to Silcox’s claim of four delivered in 1939, one source suggests that the order was actually canceled in 1935, and these were sent to the USMC – although this claim can be largely dismissed, as it is believed that the USMC use is a myth.
There are no records of any negotiations or attempts to sell the Chinese the vehicles. Even if there were, it seems possible that the Chinese would not be interested in the vehicle. According to “General of Fortune, The fabulous story of One-Arm Sutton“, by Charles Drage, the similar Sutton Skunk might have been marketed to China in late 1932, but the Chinese preparations for war against Japan were in the hands of a German military mission, headed by General Von Seekt, who did not need “talented amateurs like Sutton, nor his ingenious improvised tractor tank“.
Whilst the situation was dire in the mid-late 1930s, especially as Sino-German cooperation was coming to a close by 1938, and it might logically follow that the Chinese would now be willing to buy tractor tanks, there is no credible evidence for even the marketing of Disston Tractor Tanks ever taking place. Also, given that the Sutton Skunk was rejected, when ‘One-Arm Sutton‘ was so well respected in China, it seems unlikely that the Disston Tractor Tank was ever bought by China. If the Disston Tractor Tank was ever sold successfully to China, it is likely that a successful sale would involve Sutton, if he was not, by this time, busy with his mining operation in Korea.
The leading academic on the western armaments trade to China in the early 20th century, Anthony B. Chan was contacted, but unfortunately he has given no comment on the subject.
The Disston Tractor Tank was, frankly, a get rich quick scheme, and the quality of the machine reflects this. Whilst it might be easy to accept the slick advertisements as fact, it was still little more than a tractor, slow and overburdened with some armor plate and a pair of guns.
The Disston Tractor Tank’s production and marketing probably ended not much later than 1937, by which time, the global economy had just about recovered and armies looking for tanks could begin serious projects. The claims about China receiving tanks as late as 1938 or 1939 have not been substantiated, but could be true.
It seems more probable than not that the vehicle was marketed to more nations than recorded in this article – however, relevant documents may remain undisturbed in national archives.
37 mm (1.46 in) M1916 gun
.30 cal (7.62 mm) machine gun (probably a Marlin)
6-8mm or 6-13mm
Unknown. Using photographs, the lowest realistic estimate is at 6 (five in Afghanistan, plus one prototype). The highest estimate, albeit spurious, places it at 36. There are plenty of other estimates.
Prototype Disston Tractor Tank, circa 1933. This one was allegedly made in two hours from scrap metal. Rendition of an Afghan Disston Tractor Tank circa WW2. There were two types – most had lengthened track assemblies, but one retained the original and unmodified Caterpillar Model 35 track assembly.
Five Disston Tractor Tanks on parade in Afghanistan, circa 1937 – the fifth is just out of shot to the right, but the tip of its engine deck and tracks can just be seen. The center tank does not have a lengthened track assembly. This is the only photograph to show Disstons with their armaments.
Several Disston Tractor Tanks in Kabul. The photograph was reportedly taken by a French soldier, in March 2006 at KMTC, Pol-e-Charkhi. According to information provided by Kingston Montgomery Winget, this photo was likely taken between Forward Operating Base Scorpion and the Armor Branch School on the north-west side of Gharib Ghar, close to Range One and Two, and some old, bombed-out buildings. These vehicles are likely to have been moved apart before 2015. These all appear to have long-track suspensions – important to note, as a fourth vehicle with a short track assembly is reported at Pol-e-Charkhi.
More recent view of what appears to be the vehicle in the far right of the above. It appears as though the vehicle has rusted further and the turret and what remains of the gun have been moved. It may have been moved apart from the other three over time Courtesy of Charles Lemons.
Short-track type Disston Tractor tank, circa 2011. According to Charles Lemons, this photo was taken in the “same place” as the above. According to information provided by Kingston Montgomery Winget, this one likely located in a separate vehicle graveyard at the fence line east of the Armor Branch School, along with many old Soviet vehicles, just before the firing ranges. Courtesy of Charles Lemons.
Different view of the above. Courtesy of Charles Lemons.
Different view of above, possibly at an earlier point in time.
Disston Tractor Tank, believed to be at a garrison near Darul Aman Palace in southern Kabul circa 2006 – this is believed to be the one on display at the National Museum of Afghanistan, because it features the dummy gun and clear Afghan marking, now somewhat rusted.
A Disston Tractor Tank on display in the National Museum of Afghanistan. The museum closed in the 1990s when rival Taliban factions fought for control of nearby Darul Aman Palace. The engine grill is probably an Afghan modification to stop the engine from overheating. The gun barrel is also likely a prop, for display purposes. It was last seen near a garrison at Darul Aman Palace, close to where it was originally displayed, missing its suspension and some armor plates.
Different view of the above. Likely earlier, due to the photo being in black and white.
Different view of the above.
Drawing of a Caterpillar Model 35 tractor. These were modified by adding a new, but smaller, wheel in front of the front wheel. The new wheel was held in place by a metal bar which was riveted to the rest of the assembly. It is unclear where the exhaust pipe has been moved to.
1935 advertisement for the Disston Tractor Tank. It is believed to be the prototype design, as the suggestion of scrap metal being used to armor the original model seems to refer to the picture below. The source for this material is unknown.
Advertisement leaflet for the Disston Tractor Tank from Otto Kafka’s correspondence with Kuwait. This appears to show an unaltered photo of the above Disston prototype.View closer here.
Slightly different view of the above.
Otto Kafka’s letter on the Disston Tractor Tank addressed to the Kuwaiti Minister of War. View closer here.
Poor quality photo of several Disston Tractor Tanks. Their exact hull shapes appear slightly different to one another. Unknown location, unknown date – Likely Afghanistan circa mid/late 30s.
Another old photo of the Disston in the National Museum of Afghanistan – on its right, an Indian Pattern Mark IV.
Disston Tractor Tank in Afghan service, circa WWII. Note: This image appears to have been cropped. The original cannot be found, but a wider shot of the image can be viewed here.
Sidenote: Sutton Skunk rip-off?
The Disston Tractor Tank certainly seems to have come into existence shortly after the creation of Francis Arthur Sutton’s “Sutton Skunk“. The vehicle is believed to be made in roughly 1932, and the similarities are clear. Both vehicles were based on a tractor (an M1917 5-ton semi-armored tractor for the Sutton Skunk), both used Disston’s high-quality steel alloy plate, both were made with the intention of exports (for the Sutton Skunk, China), and both were made at Disston’s Steel Works. Based on the limited information available on both vehicles, the Sutton Skunk seems to have been developed first. The Caterpillar Company was based Peoria, Illinois, where the Sutton Skunk was made, and it may have perhaps been seen by the Caterpillar Company. The book, “General of Fortune, the fabulous story of One-Arm Sutton“, the only source for the Sutton Skunk, reveals few details on the tank’s construction. It will remain unknown if the Disston Tractor Tank was inspired by the Sutton Skunk or not.
“Mobilize!: Why Canada Was Unprepared for the Second World War” by Larry D. Rose
“A Place to Live and Work: The Henry Disston Saw Works and the Tacony” by Harry C. Silcox
“US Military Tracked Vehicles” by Fred W. Crimson
“Tanks of the World 1915-45” by Peter Chamberlain & Chris Ellis
“The Great Tank Scandal, The Universal Tank” by David Fletcher “General of Fortune, the fabulous story of One-Arm Sutton” by Charles Drage
“Armata Română şi Evoluţia Armei Tancuri. Documente. 1919-1945” by Commander Doctor Marian Moşneagu, Doctor Lulian-Stelian Boţoghină, Professor Mariana-Daniela Manolescu, Doctor Leontin-Vasile Stoica, and Professor Mihai-Cosmin Şoitariu Email correspondence with Charles Lemons, the National Defense Headquarters (Canada), the Library and Archives Canada, US Army Center of Military History, US Army Tank-automotive and Armaments Command (TACOM), Pete of vintagesaws.com
Discussions with Ian Parker, Kingston Montgomery Winget, Steve Tyliszczak, and Dean Larsen – all US soldiers in Afghanistan Esotericarmour.blogspot wwiiafterwwii.wordpress britishlibrary.typepad aviarmor.com g503.com forums network54.com forums overlord-wot.blogspot warhistoryonline.com testofbattle.com planetarmor.com
History forgets. Files are lost and mislaid. But this book seeks to shine a light, offering a collection of cutting edge pieces of historical research detailing some of the most fascinating arms and armament projects from the 1920s to the end of the 1940’s, nearly all of which had previously been lost to history.Included here are records from the UK’s MI10 (the forerunner of GCHQ) which tell the story of the mighty Japanese heavy tanks and their service during the Second World War.
Little known, the M6 was the first modern US heavy tank. The only other heavy tank built in series was the Liberty or Mark VIII, a joint US-British design, produced in 1918, of the WWI-era lozenge type. When the Second World War broke out, the successful German campaign of 1940 gave a spur to US tank development. Already, on 20 May 1940, the Chief of Infantry recommended to the US Army Ordnance Corps to study a 50-ton tank design. The first one was a projected multi-turreted model with two main 75 mm (2.95 in) turrets, a secondary one with a 37 mm (1.46 in) gun and coaxial M1919A4, and another, smaller turret with a 20 mm (0.79 in) gun and coaxial cal.30 (7.62 mm), plus four cal.30 machine guns in each corner of the tank in ball mounts. In was approved on 11 June 1940 under the ordinance prototype registration T1 heavy tank. The T1 had to be fitted with a cast hull and hydramatic transmission. However, this design already appeared outdated. In October, this design was changed to a more conventional approach, with a single turret armed with a 76.2 mm (3 in) and a 37 mm gun (1.46 in).
T1E1 and T1E2 prototypes (1942)
This second design had a single three-man turret, with a vertically-stabilized 3 in gun (76.2 mm) coupled with a coaxial 37 mm (1.46 in) gun. The turret was cast and had an electric drive and manual traverse. There was also a bow mount with twin cal.50 (12.7 mm) machine guns handled by the assistant driver. The commander cupola and some other parts were borrowed from the M3 Lee. The suspension was also borrowed from the M3, being a standard vertical volute spring (VVSS), with four bogies per side, but the tracks were doubled in width, with two rubber shoes instead of one. The upper tracks reposed on a guide rail, and the entire side was protected by a large, one-piece side skirt. The armor ranged from 83 mm (3.27 in) to 44 mm (1.73 in), while the hull was sloped. The overall weight was a staggering 50+ tons. Due to this, the main issues were the engine and transmission.
The Society of Automotive Engineers was charged with finding a suitable combination. The Wright G-200 air-cooled radial gasoline engine was initially selected and served with an electric transmission, a hydramatic one or with a torque converter. Three prototypes were ordered, but only two were delivered early in 1942 by Baldwin Locomotive Works, using the electric transmission and torque converter. One differed by having a cast hull, while the other had a welded one. On 26 May 1942, other prototypes of both series were ordered under the T1E1 designation (unofficially M6A2), with electric transmission, welded hull, 20 being built, and T1E2 (M6), with the torque converter, with a cast hull, 8 built.
The M6 and M6A1
Eventually, after many unit trials, the Ordnance Corp advised to concentrate only on the torque converter variants, and a third improved series, the T1E3 (M6A1) was ordered. Recommendations included that 115 M6s would be built for US army service and 115 others for the Allies, starting in December 1942. These series vehicles were given a two-piece cupola hatch and ring mount for an AA cal.50 (12.7 mm). The left front machine-gun was removed. However, the Armored Corps had quickly grasped the utility of having a single tank type in service, cheaper and easier to transport, such as the Sherman, and the production was stopped. The development, however, did not end there.
In August 1944, the Ordnance Corps recommended an experimental series of 15 T1E1s with a new turret, later known as the M6A2E1. Main features were a new, tall and roomy turret, similar to the one of the T29 heavy tank and a 105 mm (4.13 in) gun, giving an overall weight of 77 tons. This project was rejected by General Eisenhower.
Since the M6 was never approved for mass-production, the small series built remained on American soil, for training purposes, unit maneuver drills, and later propaganda movies, war bond tours and various related displays throughout the United States. On 14 December 1944, the M6 was declared obsolete and all but one of these scrapped, the latter now stored on display at the U.S. Army Ordnance Museum, at Aberdeen, Maryland.
Turret 83 mm (3.27 in), lower sides 70 mm (2.76 in), upper sides 44 mm (1.73 in)
Production (M6A1 alone)
M6A1, cast armor hull type, Fort Bennnings, 1942.
A -what if- prospective view of a welded type hull M6 in Italy, 1944.
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