Stridsvagn 103 ("S-Tank") (2024)

Sweden's Stridsvagn 103 [literal english: "battle wagon"] ("S-Tank" - 103 = the third tank in the Swedish army with a cannon caliber of 10 cm) was one of the more unusual modern tank. It was arguably the spiritual successor to WW2 era tank destroyers, and yet not quite. Designed to provide defensive firepower to support Sweden's armed neutrality, the unique design made it no good on offense. Armed neutrality required appearing strong enough to deter an enemy from attacking, while appearing weak enough to not look threatening. It required a force that's weak in offensive firepower, but strong in defensive firepower.

Although the S-tank was admirably suited for Swedish ambush tactics in restricted, forested terrain, its lack of a shoot- on-the-move capability made it unsuitable for general use. The US evaluated the S-tank in the mid-1970’s, but concluded that the workload of the driver/gunner was excessive.

Tanks are inherently attack-oriented weapons, designed to seize territory from the enemy. But the Swedish solution to this threat was the S-Tank, a tank without a turret. Designed to lay in wait to ambush invading enemy armor, it mounted the British L-7 105mm tank gun, the mounted on early versions of the US M1 Abrams tank.

After the Second World War, it was clear that the Swedish tank fleet was severely outdated, and several initiatives to renew armor weapon was carried out. In the early 1950s army leadership carried out studies to produce a new heavy tank for the Swedish defense. Under the code name KRV or "EMIL", the studies' purpose was to see if it was possible to develop a tank that weighed 30 tons, but still had good protection, firepower and mobility.

When the defense had the opportunity 1953 to buy the British Centurion tank, the studies were formally mothballed. Discussions in the KRV project continued informally. It was concluded that a tank was desired with: short training time adapted for conscripts, light weight, strong frontal protection, low silhouette and a big weapon.

The Swedish army discussed the development of a new generation of tanks to replace the British-made Centurion (Strv 81 and 101). AB Landsverk, Volvo and Bofors proposed to conyinue the project Tank KRV, but this was considered too expensive.

The engineer Sven Berge of the Royal Army Administration (KAF) had for several years been studying materials from the war, and based on what he had learned, he formulated a memo in the summer of 1956. The memo was received quite cooly, but because of the Berges convincing presentation, he was given more time to develop his idea. On 22 October 1956, Berge had a proposal for something better, and he was invited to the group responsible for the development of a new main battle tank.

In the following years the group worked on testing trailer parts separately, to see if it would actually work in reality. In 1958 the options were Option A (buying into an American tank, (M60 Patton), Option T (German Leopard I) and then Options S (S for Sweden).

• A-tank (A for America, probably) is the expected result from current US and UK design philosophy. It weighs about 40-45 metric tons and is frontally protected against sub-caliber kinetic penetrators fired from guns of up to 120 mm caliber, with mobility somewhat impaired by its weight. (In reality, this alternative later resulted in the M60 Patton and the Chieftain.)
• T-tank (T for Tyskland – Germany) is the expected result from current German and French design philosophy. It weighs about 30-35 metric tons and has very high specific engine power (25-30 hp/t or more), but only has frontal protection against (the equivalent of) 57 mm guns. (In reality, this alternative later resulted the Leopard 1 and the AMX-30.)
• S-tank (S for Sweden) is a proposed turretless Swedish design that has the same protection as the A-tank against kinetic weapons, while weighing only about 30 metric tons. Additionally, since the gun is fixed in the chassis, it can be fitted with screens or lattices that will protect it from all currently known anti-tank missiles and other HEAT penetrators.

For Swedish conditions, tanks should ideally weigh less than 37 metric tons. Sweden itself would develop its own tank. Tests yielded positive results, and in 1959 the army chief ordered the development of the tank to start. Orders for prototype tanks were given to Bofors, with certain parts from Volvo and Land Administration. It ordered a pre-series of 10 tanks.

Sven Berges' concept was revolutionary for the time, a tank adapted for the Swedish defense battle, compact with small target area, with the cannon directed by turning the whole vehicle. Rather than being mounted in a traversing turret, the gun was built into the hull, lowering the S-Tank's overall profile. The gun was aimed by moving the entire tank, horizontally by pivoting the tank using its tracks, vertically by raising and lowering the tank via its hydropneumatic suspension system. The Strv 103 used a very complicated suspension to accurately point the gun at the target. Coarse pointing was done with the tracks, and final aiming was done with small actuators in the suspension.

The S-tank was a very complex machine. Because the gun was aimed by moving the entire tank, it was impossible to fire the gun accurately while the tank was moving. During an attack, the S-Tank needed to come to a complete stop to position itself to aim — and then it was very vulnerable.

A turretless vehicle is easier to protect than one with a turret. The turretless vehicle is smaller, and thus difficult to spot and hit. Because there is no turret the vulnerable turret ring (always a weak spot) is no longer a problem. There is no chance that the turret will get jammed in an awkward position. The turretless vehicle can take the weight of armour normally put in the turret and use it to protect the hull instead. A turretless design is usually more heavily armored than the tank on the same chassis. The center of gravity of the vehicle is also lower, improving stability (marginally) when moving on angled terrain.

This made the tank remarkably small — the Abrams weighed nearly 70 tons, while the S-Tank weighed a mere 40 tons. Without the weight of the turret the rest of the vehicle can be built lighter, with less powerful engines and weaker suspension than the heavier turreted equivalent. This allows yet another savings in weight and resources. The gun was fed automatically by two magazines with different types of shells (flechette projectile, explosive shell or smoke grenade) with the entire supply of ammunition outside the crew compartment. The tank's crew consisted of three people: head coach, driver / gunner and a rear-driver / radio operator. A defensive tank, the S-Tank needed to be as mobile as possible. A raised screen could be erected around the entire tank to make it float, while its tracks would propel it through the water.

The Swedish Stridsvagn-103 (S-tank), featured a three-man crew. The commander’s duties were relatively conventional, but those of the other two crew members were decidedly not. The driver/gunner was seated facing forward with an integrated T-bar control, which served as driving control while the vehicle was moving, and as gun-laying controls when it was stationary.

The turretless vehicle had a fixed 105 mm cannon that was trained using counter-rotation of the tracks, and laid using hydraulic control of the 1st and 4th roadwheels on the suspension. The entire hull was effectively aimed, like a fighter plane, to point the gun. The radio operator, whose station faced the rear of the vehicle, was provided with a redundant set of driving controls. Because the vehicle lacked a turret, the only way to keep the gun and glacis armor pointed in the direction of the enemy when retrogressing was to have the vehicle back up.

Between 1967 and 1971, a total of 290 Stridsvagn 103 were delivered. The maximum production rate was seven vehiciles per month. Strv 103 was supplied to armored brigades South Skåne Brigade (PB 7), Skåne Dragon Brigade (PB 8), Skaraborg Brigade (PO Box 9) and Norrbotten armored battalions (P 5).

In the 1990s, the country retired its S-Tanks and bought the excellent German-made Leopard 2 tank. Tank 103 was taken out of service in 1997, when technical developments had outpaced the unique Swedish tank.

Opinions on whether Tank 103 was a success or a failure differ greatly. The cost of the project was SEK 665 million, of which SEK 120 million in development costs, resulting in a unit price of 2.29 million per wagon. This was about 1 million more than what the Bundeswehr paid for the first series Leopard 1 in 1964. But at its "final" battle would prove that old was possibly the best. The "battle" was conducted at an exercises in 1997, six strv 103 met as many strv 121 (Leopard 2). The strv 103 knocked out all the "hostile" tanks with only one loss.

The tactical and technical battle doctrine in the 1950s assumed that Sweden would be greatly inferior to an attacker in the number of battle tanks and other advanced weapons systems. Therefore, the concept was to respond to an attack with the tank in a combat position. This battle from fighting positions thus governed how the S-tank could be designed. In this situation Strv 103 exposed a very small target area, and the front of the vehicle was for a long time immune against known anti-armor weapons.

Using futuristic, and not fully mature, technology led course also problems in the carriage childhood and helped to give the cart a bad reputation. As the design was improved by changing packages and REMO, increased reliability so that during the latter part of his life had a significantly better availability than the Centurionstridsvagnar undergoing renovation and modification of a number of steps. It should here be pointed out that life was much longer than what was planned in the development decision.

The layout of the tank was based on the practice in the 1960s that only few contemporary tanks could shoot with gyro-stabilized guns. Since the hit probability was so low, even these tanks were forced to stop the vehicle to align the cannon with accuracy. The analysis in those days was that in practice it would be faster to get to the point and aim the gun with the tank chassis, the principle used in the idea of Sven Berge. Although comparative trials which were then made ??showed that this was true.

With hindsight, it can obviously concluded that the 1950 technical forecast was wrong in assessing that over time there would not be any radical improvement in the accuracy of tank gun firing. Modern turret tanks in most situations have a hit probability of 80%, or more when fired from a stationary position. It was therefore obvious, when Sweden selected a new tank in the 1990s, that this would have a turret. It was also unforseen that the tank came to be used much more in a mobile attack battle than originally designed. The compromises to obtain other desired properties, gave a mobility that in certain situations was limited.