Experimental, United Kingdom, WWII

UPDATED: The A39 Tortoise

The appropriately named Tortoise was a British assault tank designed with the sole purpose of attacking heavily defended enemy positions. Enormous, thickly armored and equipped with one of the most powerful anti-tank weapons of the war, the vehicle would likely have succeeded in this role.

However the war ended before the Tortoise was ready, meaning it is now most famous for its appearance in video games and as a bizarre footnote in tank design.

While it may have been a formidable assault vehicle, outside of the battlefield the Tortoise was a logistical nightmare. In fact, it was so heavy that it was used in Europe to see how German towns would cope with heavy armored vehicles should war break out with the Soviet Union.

In this article we are taking a closer look at this fascinating tank.


Origins of the Tortoises

The Tortoise story arguably starts in the 1930s, with the construction of German defences like the Siegfried Line (also known as the West Wall) that were touted as being impenetrable lines of concrete and steel. The Siegfried Line ran for 400 miles down Germany’s western border with France; from the Netherlands all the way down to Switzerland.

Covered with bunkers, cannons, turrets, dragon’s teeth and trenches, the Allies spent much time pondering on how to overcome it. Interestingly, this is the origin of the TOG, which was designed to cross heavily shelled terrain and attack fortifications, and not to combat WWI-style trench warfare as is often said.

The T28.
The US T28 was built for essentially the same purpose as the A39 Tortoise.

Britain’s response to obstacles such as the Siegfried Line was with the assault class, also known as the “Tortoise class”. These were to be heavily armored machines armed with weapons that could deal with concrete fortifications.

The US went down a similar route, creating their own assault tank that would eventually result in the Superheavy Tank T28.

Dispelling Myths

Before we continue, we need to clear up a few things.

The Tortoise is most famous for its appearance in video games. While games are great for sparking interests in history, they can also cause some misconceptions. The first of which is the Tortoise is not a tank destroyer. Yes, it doesn’t have a turret, and yes it has a powerful gun, but this doesn’t instantly class something as a tank destroyer.

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The Tortoise is a tank, as decided by its designers.

Next is a rather interesting one. Technically, it isn’t the Tortoise. Instead, there are Tortoises – Tortoise was the name of this class of tanks, and not the name of any specific vehicle. There are multiple designs all named Tortoise.


The Tortoise class of vehicles were to have a 60/40 armor distribution – which meant at least 6 inches (152 mm) of armor on the front, and 40% of that on the sides and rear.

The roof and belly were to be at least 1 inch (25 mm) thick as these vehicles were expected to go into landmine-rich environments, thus protection for the crew and engine was important.

Initially the armament was to be a 95 mm howitzer or a 6-pounder gun, which at the time was bigger and better gun than many combat tanks being produced in Britain had at the time. They would have a well-armoured body, an armoured rear section and heavy side skirts to protect the tracks.

AT.2 drawings.
A.T.2 drawings.

At this point turreted or casemated layouts were viable. Vehicles like Vickers’ A38 Valiant are tangentially linked to these requirements.

Nuffields drew up a series of designs numbered A.T.1 to A.T.10, with some featuring only small differences, while others were completely new layouts. At least one full-scale wooden mockup of what appeared to be the optimum combination of armour and armament was made. This early mockup was also called “Tortoise” and was modified slightly from time to time in line with requirements from the War Office.

On the 9th of July 1943 the design suddenly changed when the general staff required that the “Tortoise” be able to mount a new 75 mm high-velocity gun.

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This weapon was larger and heavier than the 6-pounder and required an increase in hull volume, which in turn affected the other parameters such as armour and weight leading to a new reworked body expected to be in the 65-ton region.

With the space and volume adjusted for the 75 mm gun, it was quickly realized that the vehicle could theoretically fit the new 17-pounder anti-tank gun, although this meant taking up more internal volume due to its longer recoil. The new 17-pounder vehicle was designated A.T.13

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A.T.13 had a small-scale model made by August 26th 1943, and both options were presented to the General Staff for consideration, followed by a full-scale mockup and a brochure produced.

A.T.13 drawing.
A.T.13 drawings. Note the side-mounted armament.

Around the same time Britain realised that tanks would need other means of support. This idea largely came from the disastrous Dieppe Raid the year before.

Ideally, vehicles would operate alongside tanks to support them with smoke, mine clearing, and enough firepower for immediate bunker-busting. This role went to the 79th Armoured Division later under the famed Major General Sir Percy Hobert Percy Hobart.

It was envisioned that these new Tortoises would be attached to the 79th Division as part of their specialist equipment.

By 1944 the design A.T.16 was picked as the concept to enter further development. This variant, unlike some of the others, had a centrally mounted gun. This was originally meant to be a 17-pounder, but was later changed to a 32-pounder.

The highest-mounted gun is a 32-pounder, found at The Tank Museum in Bovington.

Nuffield’s original goal was to have a lower-profiled vehicle that was faster and would not rely on specialist transport, however the adoption of the large 32-pounder gun stopped any ideas of this being a low-profile vehicle.

A.T.16 was later given the name A39, and would become the Tortoise we know now.

The Tortoise

At 72 tons with 9 inches (238 mm) of armor, it was fine tuned for the task of assaulting fortifications.

It was a casemate design to negate the vulnerabilities of a turreted tank and to make room for its powerful gun. The casemate was made from one giant casting.

The sides were covered by up to 150 mm of steel. Its almost 2 meter wide tracks were covered by thick armor plating which ran along the entire length of the Tortoise.

Armament was the massive 32-pounder gun – one of the most powerful anti-tank weapons of the war.

Tortoise gun mount close up.
The 32-pounder’s mount and shield.

This gun, often said to have been derived from the 3.7-inch anti-aircraft gun, was in fact developed from the 55-pounder. It was re-designated 37-pounder and then the 32-pounder with these being the same gun vut with different ammunition.

The 32-pounder was able penetrate over 300 mm of steel with armor-piercing discarding-sabot (APDS) rounds.

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It used two-piece ammunition, which was loaded by two loaders. It was situated in a large ball mount on the front of the hull. Despite lacking a turret, the Tortoise’s gun had a firing arc of 40 degrees each side, plus an elevation of 20 degrees and depression of 10 degrees.

Regarding crew, there was seven. Yes, seven.

Tortoise P5 in Germany.
Prototype P5, named “Arromanches” in Germany.

This was a commander, driver, co-driver, gunner, two loaders and a machine gunner. One of the crew was located in a small turret at the rear of the fighting compartment and operated its two Besa machine guns.

The suspension was comprised of 8 road wheels in a 1-6-1 configuration on each side.

Power came from a 600 hp Meteor, which, naturally, struggled to propel a tank of this size. As a result, the Tortoise had a top speed of just 12 mph on road and 4 mph off-road.

Like the US T28 though, this wasn’t a major issue as the Tortoise was designed to grind down enemy positions from the front.

Production and Testing

An order was placed for 25 vehicles, however, by 1944 the tables had turned on Germany and the defensive lines had been found to have been mostly propaganda tools. Tank production was much more efficient, and many older types had been phased out of service. This created a fear that Nuffield would loose the capability of building the Tortoise when it was ready.

As a result they were given the job of converting Centaur AA vehicles into Trailbreaker bulldozers, allowing them to keep staff and manufacturing capabilities.

A wooden mockup of Tortoise was made first, followed by an order initially for 25 vehicles. Although that number would be scaled down to just 12 vehicles by September 1945. In the end though only 6 production vehicles were finished (although it’s believed up to 12 hulls were be cast in total).

Tortoise casting.
Tortoise superstructure casting.

The Tortoise was too late to see service in the Second World War, and in all reality was not needed. The expected defensive fortifications were not as formidable as previously thought, and the majority of Germans were fighting a losing battle on the Eastern Front – the need for such a lumbering giant was not needed.

However, once the war was over they did find a use. Thanks to their enormous size and weight, plus their 32-pounder guns, they would be useful test beds.

As such, the 6 in development would be finished for this purpose. The prototypes were simply designated P1, P2, P3, P4, P5 and P6.

Prototype Fates

The first prototype, P1 (serial number AT104D), was used in the UK to compare the 32-pounder with the Centurion’s 20-pounder.

The 32-pounder’s round was devastating, proving superior in most ways other than size to the Centurion’s 20-pounder.

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P1 however was problematic, and the test team were advised not to drive it over 10 miles – which they promptly did, resulting in a serious breakdown. This tortoise differed in some ways from the others, notably, it lacks the side ammunition port for reloading.

Tortoise P1.
Tortoise prototype P1. This example survives today at The Tank Museum in Bovington.

After this, she hung around for a bit before going to Bovington in 1952. She remains here today.

P2 was fitted with a captured German gas turbine engine. This tank has confused researchers as it was listed under the name “Tortoise 2” in a few files. However, this is not a sequel. Rather, it relates to the P number – “P2”.

It was later delivered to Bovington, where it was sadly scrapped.

P3 (AT 108B A3) was used in gunnery trials after P1 broke down. It fired at Centurions, testing reload times, loader fatigue and overall accuracy. After this, her fate is not recorded but almost certainly scrapped.

Tortoise P3 prototype.
Tortoise prototype P3, with gun missing.

P4 and P5, named Athena and Arromanches respectively, were sent over to the British Army On the Rhine on the continent.

Their guns were tested in some basic firing trials, in which the large 32-pounder rounds were able to pass through a Panther easily at 1,000 yards. After this their size and weight was used to test European infrastructure to see how it would cope with heavy future tanks in a theoretical clash with the Soviet Union.

They were driven in urban areas to test road surfaces, as well as long journeys on the autobahn to see how they held up to heavy vehicle usage. Other tests were done on bridges to measure structural integrity, while fording tests were carried out as well as rafting options to carry them across rivers.

Tortoise P4 in Germany.
Tortoise prototype P4, named “Athena”, with her crew in Germany.

The fate of these two vehicles is unknown, but both were likely destroyed on German firing ranges.

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P6 (AT 108C A9) might have been the 9th casting. This vehicle was never fitted with engines or a gun and was used up as a range target in Kirkcudbright, Scotland. The wreck is still there today.

Special thanks to Armoured Archives for the images, and help with this article.