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Stridsvagn 103: Sweden’s Turretless Cold War Super Tank

Written by Matthew Copes

https://commons.wikimedia.org/wiki/File:Stridsvagn_103_Revinge_2015-1.jpg

Known for their low profiles, fixed guns, and curiously nonexistent turrets, Stridsvagn 103s were among the world’s most revolutionary armored vehicles when they entered service with the Swedish Army in 1967. 

Except for Germany’s Kanonenjagdpanzer, Stridsvagn 103s were the only heavily armed turretless vehicles produced after the Second World War.

Commonly referred to as S Tanks, in English, “Stridsvagn” means chariot, battle carriage, or simply, tank. 

Nearly all turretless vehicles with big guns produced during the Second World War were designated assault guns or tank destroyers. 

Because they shared similarities with these machines, S Tanks were commonly misclassified as the latter. 


However, they were officially main battle tanks because the roles for which they’d been built were nearly identical to those filled by traditional tanks.  

Another common misconception is that Swedish military doctrine has always been primarily defensive. 

In fact, despite the country’s long history of neutrality, its Cold War national defense strategies and tactics were largely offensive in nature. 

Now the story of the Stridsvagn 103, Sweden’s unique Cold War tank. 

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Background

In the post-war years, Sweden’s Army relied almost exclusively on tanks produced in other countries.

Weighing in at more than 50 tons and packing powerful 105 mm main guns, British Centurions were among the era’s most lethal main battle tanks. 

By the late ‘60s, Sweden had more than 300 Centurions in service, but they were expensive to operate and had been designed to slug it out with large formations of Soviet tanks streaming across the plains of western Europe. 

On the other hand, Sweden’s abundant mountains, forests, and swampy areas weren’t well suited to heavy tanks, and because Centurions weren’t domestically produced, getting spare parts could be tricky in times of crisis. 

Because these issues were evident as early as the mid-’50s, the Swedish Army sought to replace its foreign-built tanks with domestically produced ones. 

To that end, the Ordnance Department issued a contract tender to several Swedish manufacturers, most of which had formed multi-company consortiums to share technical data, speed development, and spread the financial risk associated with developing an entirely new machine. 

Initially, the Army considered continuing the development of the KRV medium tank that had been designed in secrecy a few years earlier. 

At just 25 tons, KRVs featured oscillating turrets and massive 155 mm smoothbore cannons that had far greater range and stopping power than nearly anything they were likely to encounter on the battlefield. 

Early prototypes showed promise, but because they had dangerously high profiles and thin armor, KRVs never progressed past the prototype phase. 

With the revamped KRV program dead on arrival, Swedish arms manufacturers began designing a new tank from the ground up. 

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Design

More than three-quarters of the tanks hit or knocked out during World War II took rounds in their turrets instead of their hulls. 

This isn’t surprising since turrets are traditional tanks’ highest and most visible parts.  

The Swedes deduced that turretless vehicles would be harder to see and hit, and that survivability rates for both men and machines would increase dramatically. 

In addition, turretless armored vehicles were generally lighter, less expensive, and more mobile than regular tanks, all of which made them attractive alternatives. 

After reviewing proposals submitted by various manufacturers in early 1958, the Swedish Army commissioned Bofors to build two prototypes of its design for additional testing. 

By the spring of 1961, the Army was so pleased with S Tanks’ performance that ten pre-production units were ordered for more thorough analysis. 

Tipping the scales at 42 tons and measuring 26 feet (7.9 m) long from nose to tail, S Tanks were just slightly over 7 feet (2.2 m) tall. 

This was far lower than Centurions which were nearly 10 feet (3 m) tall, and American M60s which were almost 11 feet (3.2 m) tall. 

But ironically, S Tanks were only slightly lower than the turreted Soviet T-62s they were most likely to square off against in combat. 

Featuring squat, heavily armored, dome-shaped turrets, T-62s suffered from several inherent design flaws, one of the most significant of which was a lack of gun depression. 

With the muzzles of their main guns pointed down, the breech’s upward travel was inhibited by the ceiling of the turret. 

This put T-62s at a major disadvantage when firing at targets below them from “hull down” positions.

But whereas T-62s had fully traversable turrets, S Tank guns were fixed. 

In other words, the whole vehicle had to move to get the cannon lined up on its target. 

This difficult task relied on a complex hydropneumatic suspension system that automatically raised and lowered the vehicle’s front, rear, and sides in response to input from the gunner. 

Oddly enough, with their rear ends raised to maximum height and their front ends lowered as far as they’d go, S Tanks had better depression than T-62s. 

The computer-managed system worked remarkably well, but firing on the move was out of the question because fixed guns can’t be stabilized. 

However, Swedish designers knew that even tanks with stabilized guns rarely fired while moving, and when they did, they seldom hit their targets.

As main armament, S Tanks featured Bofors-built variants of the reliable and battle-tested Royal Armament L7 105 mm rifled cannons similar to those found on Centurions and M60s.

Designated L/62, the Bofors cannon used the same ammunition as its British cousin, but S Tanks were equipped with autoloaders capable of getting off nearly 20 rounds per minute under optimal conditions. 

Internal storage allowed 50 rounds to be carried, and spent casings were ejected through a hatch in the rear of the hull after each firing. 

With a muzzle velocity exceeding 3,700 feet per second (1,100 m/s), direct-fire range was approximately 4,500 yards.

Secondary armament consisted of two fixed 7.62 mm KSP 58 machine guns in the hull, and another gun on a swivel mount just above the commander’s cupola. 

S Tanks packed formidable punches, but with just 70 mm of armor up front they were relatively thin-skinned. 

However, thanks to severely angled upper and lower glacis plates, the armor’s effective thickness was far greater than its actual thickness. 

Since incoming rounds typically hit a sloped surface, most deflected up or down instead of penetrating the crew compartments. 

At just 40 mm, side and rear armor was even thinner, but crews were trained to disengage whenever they were at risk of being outflanked. 

Later variants were equipped with removable slat armor that offered additional protection against high-energy-anti-tank (HEAT) rounds. 

Another critical consideration during the design process was keeping crew size as small as possible. 

Whereas most tanks were crewed by a commander, driver, gunner, and loader, in the early going it was considered feasible that S Tanks could function effectively when crewed only by a well-trained commander and gunner-driver. 

However, even with the autoloader the workload would have been overwhelming in combat and when performing routine tasks and maintenance in the field. 

To improve efficiency and survivability, a third crewman and duplicate controls were added.

Consoles and controls were simple, ergonomic and rugged, and the forward facing driver and commander could perform one another’s duties when necessary. 

The third crewman faced backward and could only operate the radio and drive the tank in reverse, but duplicate controls made S Tank crews far more efficient in nearly every situation. 

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Engines and Performance

Despite limited interior space, each S tank had two engines – one diesel and one gas turbine. 

The less powerful but more fuel-efficient diesel moved the tank at relatively low speeds, whereas the gas turbine kicked in when more power was required, like when traveling on a finished road at high speed. 

Though both were underpowered, early S Tanks entered service with 240 horsepower Rolls-Royce K60 diesels and 290 horsepower Boeing 502 turbines. 

Later variants got 300 horsepower turbocharged Detroit Diesel 6V53s and 500 horsepower Caterpillar gas turbines. 

With a drastically improved power-to-weight ratio, top speed increased to 37 miles per hour (50 km/h).

Depending on speed and conditions, power was sent from one or both engines through independent transmissions to an elevated final drive sprocket at the front of the tank. 

The diesel engine’s transmission had two forward and two reverse gears, giving S Tanks the ability to move forward and backward at the same speed, though this wasn’t the case with the turbine. 

This feature allowed the tank to keep its heavier frontal armor pointed toward the enemy even when retreating. 

Range was about 250 miles (402 km), but could be nearly doubled with the addition of fuel cans affixed to racks over the tracks on each side of the vehicle. 

On the downside, this extra fuel wasn’t connected to the internal fuel system and had to be added manually from outside the tank.

Thanks to easily erected flotation screens that extended more than 3 feet (.9 m) above the top of their hulls, S Tanks were also fully amphibious.

The thrust generated by the moving tracks propelled each tank at about 3.5 miles per hour (5.6 km/h) in calm water. 

Initially, one tank per unit was fitted with a dozer blade mounted on the underside of the front hull, but unlike those on civilian bulldozers, S Tank blades had to be fixed into position manually with pins and struts. 

The blades were generally used to excavate shallow depressions and construct defensive berms, and when fully retracted they provided additional armor protection to the lower portion of the hull. 

Flaws

With two engines, two transmissions, duplicate controls, and computer-actuated suspensions coupled to advanced gun sites, critics claimed that S Tanks were needlessly complex and that battlefield reliability and lethality would likely suffer. 

S Tanks were also susceptible to neck-jarring front-to-back oscillations when traveling at medium and high speeds, thanks to their short wheelbases consisting of only four road wheels.  

In addition, the protruding muzzles often penetrated the earth when obstacles like berms and embankments were encountered because the guns were fixed. 

In cases like these, soil, vegetation and rocks could become lodged in the barrel, after which thorough and time-consuming cleanings were required before firing. 

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Service 

All told, Bofors manufactured nearly 300 Stridsvagn 103s that made up the lion’s share of Sweden’s armored forces between 1967 and 1997. 

Development and procurement costs topped 665 million Swedish Kroner, or about 500 million USD when inflation is taken into account. 

Though early variants were capable and reliable, later models had more powerful engines, better suspensions, and improved fire control and thermal imaging systems, the latter of which allowed them to operate effectively at night and in poor weather. 

During conflicts, S Tanks would have been tasked with carrying out counteroffensive actions against enemy armored units, but since they never saw combat, the design remains largely unproven. 

But though they never fired their guns in anger, S Tanks did fare well in mock combat exercises when pitted against turreted main battle tanks like British Centurions, American M60s, and German Leopard 1s. 

Shortly after entering service with the Swedish Army, S Tanks were put through their paces at the British Armor School in Bovington, where they proved to be just as lethal as their English counterparts. 

Two S Tanks were also tested at the American Armor Center at Fort Knox, Kentucky in the late ‘70s, where they performed well against M60A1E3s.  

Yet despite international acclaim, no S Tanks were ever exported. 

Norway considered equipping its armed forces with Stridsvagn 103s in the late ‘60s, but ultimately opted for Leopard 1s instead. 

In 1980 – nearly two decades before they were finally retired – the Swedish Army considered phasing out its S Tanks and replacing them with Stridsvagn 2000s. 

Unfortunately, the futuristic Stridsvagn 2000 never made it past the prototype phase, and 103s remained in service until 1997, after which they were replaced by domestically produced variants of Germany’s Leopard II. 

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