The British Army "Tortoise" (Tank, Heavy Assault, Tortoise A39) was one example in the seemingly long line of "super heavy tanks" being entertained, and, in some cases, reaching development by all sides in World War 2. Many of these wartime designs fell to naught or appeared in just a handful of developmental forms with the Tortoise being no exception. By early 1943, Allied warplanners were beginning to flesh out the results of a direct European land invasion of Nazi-held territories. After a foothold was presumably established, it would be the "bloody business of the day" to advance ever closer to Berlin and bring a timely end to the war in Europe. As such, the Allies were beginning to estimate the level of German defenses throughout that journey and correctly deduced that there would, no doubt, be a strong and disciplined response from Hitler and his fanatical followers. The Tortoise was, therefore, developed to counter the expected heavily fortified German defenses, specifically those to be found on the fabled "Siegfried Line".
The "Siegfried Line" was an impressive defensive front developed as a response to the French "Maginot Line", itself constructed from 1930 to 1940. The Siegfried Line was a defensive array of forts and anti-vehicle defenses intended to hamper - or halt - any advancing ground army. The front stretched along some 390 miles of land and was made up of over 18,000 fortified bunkers connected via an underground network of tunnels. Hitler made plans for a counter to the Maginot Line as early as 1936 and the German defensive line was subsequently installed from 1938 to 1940. The Tortoise, it seemed, would be born for such a role.
The British had already begun attempts to turn several of their existing tank platforms into assault tanks by adding more potent armament and more armor protection. Having been convinced of the dedicated "assault gun" concept, a general directive was issued in April of 1943 for a powerful heavy system to match the requirement. No fewer than 18 designs were submitted by the Nuffield Organization as concept "AT1" through "AT18". Design AT16 was eventually agreed upon by the British Tank Board who ordered it as a batch of twenty five production vehicles based directly on the mockup, thusly negating the need for any time-consuming pilot (prototype) models. The hope was to have the new weapon system installed in British Army service by September of 1945, operating as part of the 79th Armored Division - a specialized British armored division set up on August 14th, 1942 as part of the Normandy landings in France to be conducted on June 6th, 1944.
Design on the Tortoise began in 1944 with a focus placed on stout armor protection, in effect sacrificing mobility and general performance in the process. Additionally, the design would fuse the main armament within a hull superstructure itself, doing away with a complicated turret system and its inherent weight ensured the Tortoise would be a solid gunnery platform for which to fire the powerful main armament from. This type of thinking played well to the strengths of the Tortoise, whose primary mission had always been to engage and clear away enemy fortifications, assuming Germany would clearly be fighting a defensive war within time.
However, the war in Europe more or less ended in late April of 1945 with the suicide of Hitler and Japan capitulated in the Far East in August that same year. While already under construction, the original Tortoise production order was curtailed to just six of the production vehicles and only a single example was ever delivered for evaluation in Germany where it was found to be an adequate and stable mount - the only true drawback being its weight, making transportation a time consuming ordeal and requiring the use of established railways. Only the six Tortoise tanks were eventually completed in all and non were ever used in operational combat nor was the tank placed into serial production. Like many other high-level developments for the Allies by war's end, the end of the war itself had proven a death sentence of sorts to projects such as the Tortoise. The lucrative defense contracts that seemingly "flowed like water" during wartime were now a thing of the past and programs were either cut back, abandoned or scrapped where they stood.
Design of the Tortoise generated quite a unique appearance when compared to other armored vehicles of this class during the war. The system was propelled by a pair of wide track systems fitted to either side of the hull, its road wheels tied to a torsion bar suspension system. The tracks would have had armored "skirts" for increased protection to the hull sides and the critical road wheels. The engine was fitted to a compartment in the rear for maximum protection of this key component. There was no conventional turret but a fixed superstructure instead. The superstructure held an relatively sloped front facing - with a noticeable protruding mantlet - and slab-sides with a straight top. The hull and superstructure were heavily armored to bear the brunt of any enemy return fire and contained the main gun armament as well as secondary armament in the form of Besa type machine guns. Circular access hatches were located atop the superstructure installation. Overall armor protection thickness ranged from 178mm to 228mm. The main gun extended from the mantlet and was held in place by an inverted "vee" support bracket during transport sessions. The main gun was capped by a muzzle break at its lethal end. At any angle, the Tortoise provided for a most imposing look. She was to be crewed by seven personnel made up of a driver, co-driver, tank commander, gunner, a pair of projectile loaders for the main gun and a dedicated machine gunner.
Primary armament centered around the powerful Ordnance QF 32-pounder (94mm) main gun, a derivative of the proven British 3.75-inch anti-aircraft gun. The armament, while set within the fixed hull superstructure, was actually given a slight amount of powered traverse for assisted aiming though, generally, the turning of the whole vehicle in the direction of the target would have been quite normal. Operation of the gun stemmed from direction received from of the commander followed by a timely response from the two loaders - inserting both charge and projectile - and finally the all-critical aiming and reaction of the designated gunner. The QF 32-pounder was supplied an armor piercing (AP) round weighing no less than 32 pounds (hence the armament designation). During evaluation, the weapon and its projectile were able to pierce the armor of the impressive German Panther series of medium tanks, this recorded at a distance of some 1,000 yards away. Should the Tortoise ever have gone into production, this armament would have been quite a lethal addition to the British inventory.
Self-defense - usually to counter direct infantry grenade actions - was supplied from a trio of 7.92mm Besa machine guns. One was fitted within a ball mount to the left of the main gun. Though traverse from this mount would have been somewhat limiting, it supplied a good field of fire for the crew when tackling targets direct ahead of the vehicle. The remaining pair of Besa machine guns were fitted along the top of the superstructure.
Operating weight of the Tortoise would have been in the vicinity of 79 tons, making the Tortoise one of the heaviest completed tank developments of the war. Her running length stood at 33 feet with a width nearing 13 feet and a height of 9.8 feet. At such dimensions and weight, the Tortoise would of had a tough go of it when attempting to traverse the old-style streets and bridges of France, Belgium, Holland, Denmark or Germany all herself. The system would have no doubt made use of the established railway network across Europe for "express relocation" actions. Power was supplied from a single Rolls-Royce Meteor V12 gasoline engine delivering up to 600 horsepower of output. As it stood, this gave the tank a top speed of just 12 miles per hour on paved roads and no more than 4 miles per hour off-road. Operational range was listed at just 87 miles.
While both a battlefield liability and a powerful addition, the Tortoise is an oft-forgotten part of British tank development concerning World War 2. In reality, she would have been on par with many of the heavy assault systems being fielded by the Germans by the late-war years and would have gone on to supply the British Army with a capable assault system to help even the playing field to an extent. While generally referred to as a "super heavy tank" and formally categorized as a "heavy assault tank", the general design of the Tortoise - with its fixed armament in a hull superstructure - was more akin to an assault gun or self-propelled gun (SPG)system than a "true" tank - which typically operated with a traversing turret system.
One of the existing Tortoise tanks - having survived both the war and the ensuing post-war politics - can be found today as part of the Bovington Tank Museum collection in Bovington, UK.