In 1942, and in somewhat of a panic over the state of their heavy tank program,
Britain asked the United States to begin a joint project to create an assault tank. The American
design would culminate in the T14, while the British would create the A33 “Excelsior”.
But after nearly 3 years of development, the project was cancelled in late 1944, with only
4 vehicles produced out of a planned 8500. Both designs had their merits, so why did all this work
go to waste? What killed the allied assault tanks?
To get to the bottom of this we must first look at
the vehicle that Britain had produced before the project began, namely the A22 Churchill.
Churchill was not a heavy tank nor was it an assault tank, it was an infantry tank.
These vehicles, in British armoured doctrine, would be relatively slow but heavily armed and
heavily armoured and would accompany, as the name suggests, the infantry.
The Churchill design was based on the rather incorrect assumption that a second world
conflict would play out much like the first – trench warfare, muddy terrain,
and mostly frontal assaults. In fact, very early designs had sponson-mounted 2 pdr guns,
and a turret was only added on later.
Britain was concerned that the Churchill was outdated.
Its 2 pdr main armament, while still being relatively potent in the early war period,
was not an effective assault weapon, and so Churchills mounted a 3 inch howitzer in the front
of the vehicle to destroy fortifications and emplacements. The design was cumbersome, slow,
unreliable and largely outdated, as would be proven in the Dieppe Raid of late 1942.
Of course, the Churchill was not the only reason this raid failed,
but the British wanted a new tank that would eventually replace it, perhaps as early as 1943.
Meanwhile, across the pond, the US Army had developed their own heavy tank, the M6. And boy,
was it heavy. 57 metric tonnes of American steel. It featured a large turret with a high
calibre gun, double wide tracks, thick frontal armour, and armoured side skirts. The Americans
had been working on this design for a number of years and clearly had some idea of how to make a
modern heavy tank, despite the M6 slightly falling short of what the US Army had originally wanted.
And so, Britain asked them for help. They proposed a joint project, and wanted the
Americans to design an assault tank to their specifications, while the British would work
on their own competing design using some American components and knowledge. The British wanted to
order 8500 of the chosen vehicle, and so to aid logistics the American design would be
loosely based on the M4 and the British design would focus on adapting the A27 Cromwell.
The influence of the M4 on the American design is immediately apparent, and it’s easy to dismiss
this vehicle as just some fat Sherman, but the T14, as this vehicle would be known, was
a completely new design. It did use the Sherman’s transmission and drivetrain, and mounted the same
75mm gun, but the similarities largely end there. The armour on the T14, while being the same 2
inch thickness as the M4, was sloped at a much steeper angle of 60 degrees, giving the vehicle
more than 100mm of effective protection. The transmission cover’s armour was also increased,
with the front of the cover being cast at 4 inches thick. Even the side and rear of the hull
were 2 inches thick, and angled at 30 degrees. The new turret was also much better protected,
with the front offering 3 inches of protection sloped at 30 degrees,
and the sides and rear were 4 inches thick. It was an incredibly impressive armour layout,
considerably better than anything the British or Americans had at this point in the war.
However it was also incredibly heavy at nearly 43 tons. This was more than 10 tons heavier than
the Sherman, and thus required a more powerful engine. The Sherman M4A3 used the Ford GAA V8, but the
T14 had the more powerful GAZ, with space left for a possible upgrade to a V-12 engine down the line.
T14 used double wide tracks to try and spread out this extra weight, and used
the same suspension as the M6 – HVSS bogies arranged in pairs along the length of the hull.
With the extra weight, the T14 managed a top speed of around 24 mph.
It was a little slow, but considering its protection and the role it was designed for,
it was acceptable. The Churchill could only manage around 15 mph for example.
One of the more unique features of the T14 is the addition of side skirts. T14 was being
designed for use by the British, remember, and they felt it necessary to protect the sides of
the vehicle and the suspension where possible. These so called “bazooka plates” were either an
inch or half an inch thick, and hung down over the sides of the hull. But more on that later.
The British A33, originally meant to be a modified Cromwell, ended up sharing
pretty much nothing with the original A27. It’s predecessors, the A28, A31 and A32,
were much more similar to the Cromwell, and attempted to add armour to the vehicle while
retaining the 5 wheel Christie suspension system. These were abandoned in favour of the A33, which
would use a brand new suspension design. Or to be more accurate, 2 different suspension designs.
The A33, made to the same specification as T14, had very similar armour protection,
but it was achieved slightly differently. Instead of sloping a thinner plate, the A33 would simply
thicken the armour of the Cromwell, with the front plate being increased to 4 and a half
inches and the lower frontal plate 2 inches, but angled at 70 degrees. The inner side armour was 2
inches thick, but the vehicle did enjoy increases protection from the 1 inch thick side skirts.
The turret protection was very similar, with the front being increased to 4 and a half inches,
the sides 3 and a half, and the rear being 3 inches, the same as the rear of the hull.
But not all A33s looked like this one.
The first A33 pilot, known as A33/1 or A,
would mount the same suspension system as the M6, and by extension, the T14. You can
see in this image the early pilot, with it’s M6-style side skirts, but including the very
British side escape hatches. These side hatches would have a 1 inch thick steel tube connecting
them to the crew compartment through the middle of the tracks. Definitely not somewhere I would
like to be stuck in a life or death situation, especially given the small size of these openings.
This vehicle would mount the 6 pounder as planned, would weigh in at around 40 tons, and was powered
by the Rolls Royce Meteor engine, the same as Cromwell apart from a few minor modifications.
The A33 would enjoy almost exactly the same top speed as the T14, around 25 mph.
Pilot versions of both the T14 and A33 were built and then tested throughout 1943. The M6 style
suspension proved troublesome. American reports mention the bogies being damaged, especially the
outside centre set. This report also mentions the fact that the vehicle would frequently
throw its tracks, and recommends serious improvements to the entire suspension system.
But perhaps the most infuriating aspect of the design was the side skirts,
especially when the suspension system needed constant repair and replacement.
Every time track access was required, these plates needed to be folded up or removed entirely,
making regular maintenance incredibly difficult. British testing came to largely the same
conclusion, although they seemed to have far less issues with the suspension itself.
After a 1000 mile test, the Brits only had some minor complaints. The vehicle
picked up over 2 tons of mud during this trial, which apparently didn’t affect the performance,
but obviously wasn’t ideal. They had been working on their own
suspension design, using more grippy tracks, which would be implemented on the 2nd pilot,
known as A33/2 or A33 B. This vehicle mounted the upgraded suspension system, known as the R-L Type,
which was also bogie based, but was meant to improve reliability and ride quality. In actuality
this suspension was complicated and expensive, and was not without its own reliability issues.
But, due to the change in suspension, the 2nd pilot mounted side skirts which covered the
entire hull. It also was produced with the QF 75mm gun, to match the Cromwells upgraded
armament at that point in the war. The first pilot was retrofitted with this weapon as well.
You might’ve noticed that I have been very well behaved and only referred to the A33
as the Excelsior once, in the intro. This is because the A33 was never called the Excelsior.
The name doesn’t appear in any of the literature surrounding A33 and nobody is quite sure where it
came from. A more likely name that was at least mentioned, was “Commodore”, but this name has
also been attributed to another vehicle, the A40. So probably safe just to call it the A33 for now.
The A33 and T14 were both good vehicles that met the specification and by all accounts would’ve
been fit for purpose. However, during these vehicle’s development the Churchill had got
some serious upgrades. It had become much more reliable, mounted a 6 pounder gun in a new,
thicker turret, had thicker armour and had eliminated the 3 inch howitzer. It really made
no sense to attempt to replace Churchill with the war so evidently about to come to a close.
The Americans had only ever had very limited interest in the T14,
but this interest had faded long ago and they had in fact fielded their own assault tank,
the Sherman Jumbo, which was performing relatively well. The T14 and A33 just weren’t
needed anymore, and both projects were shelved. In the end, two pilots were made of each of these
vehicles. The first pilot in both cases was lost – the T14 was scrapped and the A33 A was lost after
being used as a range target. The 2nd pilot of both vehicles survives however, and are both on
display in the Tank Museum’s Vehicle Conservation Centre if you want to pay them a visit.
I want to say a quick thank to Anson and ArchieB from the channel’s Discord for giving me the idea
for this video. If YOU have any suggestions, feedback or just want to hang out and chat,
I’d love to see you in the Discord as well, link in description. As always,
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