Stridsvagn 103

The Stridsvagn 103 (Strv 103), also known as the Alternative S and S-tank, is a Swedish Cold War-era main battle tank, designed and manufactured in Sweden. "Strv" is the Swedish military abbreviation of stridsvagn, Swedish for tank (literally combat wagon, it also is the Swedish word for chariot), while the 103 comes from being the third tank in Swedish service to be equipped with a 10.5 cm gun.

Developed in the 1950s, it was the first main battle tank to use a gas turbine engine and the only mass-produced tank since World War II to not use a turret besides the German Kanonenjagdpanzer, which is not classified as a tank by role, but by design. It has an unconventional design with a unique gun laying process: it is turretless with a fixed gun traversed by engaging the tracks and elevated by adjusting the hull suspension.

While most turretless armoured fighting vehicles are classified as assault guns or tank destroyers, the Strv 103 is considered a tank since its designated combat role matched those of other tanks within contemporary Swedish doctrine.

History

Concept development

In the early 1950s, the Royal Swedish Army Materiel Administration's Ordnance Department began development of a new tank known as kranvagn, or KRV. The desired features were a weight around 30 tonnes with high gun performance, protection and mobility. The new design emerged with a very low-profile hull with a tall and highly angled turret mounting a large-calibre main gun and autoloader system, reducing the crew to three. 105 to 120 mm guns were initially considered, with the 120 being favoured, and later a 155 mm design was also considered. The overall design is very similar to the French AMX-50. This made it impossible to use a stabilised gun. As a result, the tank could not accurately move and fire at the same time, but the Swedish experience with Centurions suggested that, in order for tanks to reach acceptable accuracy, they would need to come to a halt anyway, and erroneously estimated that no breakthrough in stabilisation technology was likely within the foreseeable future.

Other features of the tank were also quite radical. The rifled gun, a Bofors 105 mm L74 with a barrel length of 62 Calibers, was able to use the same ammunition as the British Royal Ordnance L7, and would be equipped with an autoloader allowing a rate of fire of one round every three seconds, also allowing the crew to be reduced to two; a gunner/driver and the commander (most designs of the era used a crew of four), with one person being able to handle all functions of the tank from the ordinary position due to duplicate controls. This would of course only be used in emergencies, as the workload would be overwhelming, but apart from providing redundancy it also allowed the crew to shift tasks between them as situation required. The concept went through practical tests, that quickly revealed that a two-man crew would not be self-sufficient when considering the many tasks not directly related to handling the tank: in particular, routine maintenance, bivouacking, track-changes and reloading in field. While the last issue could have been solved by adding staff to the ammunition crews, it was decided that a third crew-member was needed. To enhance combat effectiveness, the third man was to be assigned as a rear driver/radio operator, facing the rear of the tank and equipped with a complete setup for driving. This allowed the tank to be driven backwards at the same speed as forwards, keeping its frontal armour pointed at the enemy, while relieving the commander of routine radio duty. The commander and gunner/driver both had the same set of sights and controls to fire the gun and drive the tank.

The tank was uniquely powered by two different kind of engines, a Rolls-Royce K60 opposed-piston diesel for slow cruising and manoeuvring the tank in aiming, and a Boeing 502 turbine for more power when travelling at higher speed or in severe terrain. The turbine was quickly found to be underpowered, and was replaced by a Caterpillar turbine delivering after no more than 70 tanks had been produced, and retrofitted to all previous vehicles. This was the first use of a turbine engine in a production tank; the Soviet T-80 and US M1 Abrams would later be built with gas turbines for main propulsion. The concept was interesting enough that Bofors was asked to build a prototype of the suspension/drive train, which they completed successfully.

The Strv 103 could be made fully amphibious. A flotation screen could be erected around the upper hull in about 20 minutes, and the tracks would drive the tank at about in water.

One tank in each platoon was fitted with a dozer blade under the front hull, which was from outside the tank manually dropped and locked into working position with pins and support struts. The blade allowed it to do simple engineering tasks, like digging fire pits for the platoon, filling trenches for ease of passage and so forth. Once the task was completed, the blade was again manually returned to the position under the front hull and locked in place. Upon the introduction of the 103C model all tanks had a bulldozer blade fitted, both to speed up operations and for the increased protection of the lower hull.

Service

thumb|right|The Strv 103 demonstrating its amphibious capabilities with the help of flotation screens.

In preparation for the defence plan of 1958 (Försvarsbeslut 1958 (FB58)) in Riksdagen (Swedish parliament), the procurement set Alternativ S against the two foreign alternatives Alternativ A and Alternativ T. While the domestic alternative was going to be more expensive, the defence committee report recommended "S" when weighing in the symbolic value of a domestic tank for a neutral country as well as the spin-off effects on Swedish industrial competence.

Riksdagen made the formal decision regarding FB58 on 4 February 1958, and a follow-on contract called for two production prototypes, which were completed in 1961. By this point, the army was so satisfied with the design that an initial pre-production order for 10 was placed in 1960.

With minor changes, the Alternativ S was adopted as the Stridsvagn 103 ("103" from being the third tank with a 10 cm calibre gun accepted into Swedish service). Full production started in 1967 and ended in 1971 with 290 delivered. The changes included a new gyro-stabilised commander's cupola armed with a 7.62 mm KSP 58 machine gun, and upgraded frontal armour. A unique slat armor grid could be mounted at the front to help defeat high-explosive anti-tank (HEAT) rounds; however, it was kept secret for many years and was to be fitted only in the event of war.

Despite its design, the Strv 103 was intended for offensive operations. The armoured brigades of the Swedish Army, which operated the Strv 103, were designated anfallsbrigader (assault brigades) and tasked with launching counter-offensives on enemy beachheads and airborne landings. The stated Swedish armoured doctrine contemporary to the tank describes an aggressive approach to armoured warfare, even in defensive situations. The design of the Strv 103, with its low profile, was based on protection rather than defensive battlefield behaviour.

Performance

The Stridsvagn 103 never saw combat and so its design remains unproven. However, for its intended role in the 1960s, it had numerous advantages. In 1967, Norway carried out a two-week comparative observation test with the Leopard 1 and found that, with closed hatches, the 103 spotted more targets and fired faster than the Leopard while the situation was reversed when operating with hatches open. In April to September 1968, two 103s were tested at the British armour school in Bovington, which reported that "the turretless concept of the "S"-tank holds considerable advantage over turreted tanks". In 1973, the BAOR tested the 103. British crewmen received six weeks training and the vehicles were serviced by Swedish engineers. Over nine days of manoeuvres alongside the Chieftain tank, availability never fell under 90% and the final report stated, "It has not been possible to prove any disadvantage in the "S" inability to fire on the move." In 1975, two 103s were tested at the American armour center at Fort Knox. The trial demonstrated that the 103 fired more accurately than the M60A1E3, but on an average of 0.5 seconds slower. In the late 90s, a wargame was held in Kvarn pitting 7 Strv 103s in a defensive position against an equal amount of Strv 121s (Leopard 2). All seven Strv 121s were knocked out while only one 103 was lost.

Variants

right|thumb|Strv 103C at the [[Swedish Army Museum, Stockholm, with anti-HEAT slat armor on the front]]

; Stridsvagn 103B: As the weight of the Strv 103 had increased compared to the pre-production tanks, the 103 turned out to be under-powered. Hence, a more powerful version of the same gas turbine, manufactured by Caterpillar, was introduced after the first production run of 80 tanks. The early version tanks (retroactively designated Strv 103A) were soon upgraded to B-standard. Adjustments to the hydro-pneumatic suspension increased elevation range from −10 through +12 degrees, to −11 through +16 degrees.

; Stridsvagn 103C: An upgrade programme was started in 1986 to fit all vehicles with improved fire control systems. Also, each Strv 103 was fitted with a dozer blade, rather than just one per platoon. A further upgrade in 1987/88 replaced the Rolls-Royce engine with a newer Detroit Diesel with more fuel cans placed along the sides to function as applique armour, and added a new laser rangefinder.

thumb|right|The proposed Strv 103D upgrade

; Stridsvagn 103D: In the mid-1990s, as the Swedish Armed Forces were looking for a new main battle tank, one Strv 103C was upgraded into the Strv 103D. The major changes were the installation of fire-control computer, thermal viewers for both the gunner and the commander, allowing the crew to fight at night-time and in bad weather conditions, and the installation of passive light enhancers for driving. Some minor changes to the suspension system and engine were also made. There was some consideration of adding both reactive and/or appliqué armour in the early 1990s, but, in the end, the Strv 103 was instead phased out of Swedish service in favour of the Stridsvagn 121 (leased Leopard 2A4s were used as a stop-gap measure), which entered service in 1997 (the last year that the Strv 103 was used to train tank crews). together with some 103C models. They are all still in running order.

thumb|right|MV 103C Deminer.

; Minvält 103C: The MV 103C Deminer was a minesweeper vehicle based on the 103C tank. The project was discontinued in 1997.

;15,5 cm bandkanon 1:Self-propelled howitzer developed from Strv 103 chassis.

Tanks on display

The following exhibitions possess an S-tank on display:

Sweden:

Försvarsmuseum Boden, Boden through Föreningen P5
Försvarsfordonsmuseet Arsenalen, Härad, Sweden
Swedish Army Museum, Stockholm
Beredskapsmuseet, Helsingborg

Denmark:

Aalborg Forsvars- og Garnisonmuseum

Germany:

German Tank Museum (Deutsches Panzermuseum Munster)

UK:

The Tank Museum, Bovington

Australia:

Royal Australian Armoured Corps Memorial and Army Tank Museum

France:

Musée des Blindés, Saumur

Russia:

Kubinka Tank Museum

Belgium:

Gunfire Museum, Brasschaat

References

Sources

Stridsvagn 103 S (E1995.105) at The Tank Museum
Historien bakom Stridsvagn 103 "S"

External links

Society S-tank – Welcome to The S tank association – official site of the S tank association
"Vapenverkan mot Stridsvagn 103" 20:28 minutes, English subtitles
"Tank Chats #117 | Stridsvagn 103 | The Tank Museum, Bovington UK. Curator David Willey discusses the Cold War era Swedish Stridsvagn 103, also known as the 'S-Tank'.