Stridsvagn 103 The Stridsvagn 103 ( Strv 103 ) , or S - Tank , was a Swedish tank ( although some consider it to be a tank destroyer ) . It was known for its unconventional turret - less design , with a fixed gun traversed by engaging the tracks and elevated by adjusting the hull suspension . The S - Tank was developed in the 1950s and was the first main battle tank to use a turbine engine . The result was a very low - profile design with an emphasis on defense and heightened crew protection level . S - Tanks formed a major portion of the Swedish armored forces during the 1960s , 70s , 80s and part of the 90s , but have since been removed from service in favour of the Leopard 2 . History . In the mid - 1950s the Swedish army put out a contract tender for a new tank design to replace their Centurion s . Although the Centurion was arguably the best tank in the world at the time , its performance lead over contemporary Soviet designs like the T - 55 was only marginal , and any future designs would best it . A consortium of Landsverk , Volvo and Bofors responded with a new heavy tank design , known under the codename KRV , fitted with a 155mm smoothbore gun in an oscillating turret . But this would be an expensive option and the Army started looking at British , German and American tanks . Sven Berge of the Swedish Arms Administration then in 1956 proposed " Alternativ S " , a domestic alternative ( S stands for Swedish ) . Noting that the chance of being hit in combat was strongly related to height , he proposed that any new design should be as low as possible . The only practical way to do this was to eliminate the turret ( which would also make the tank much lighter and simpler ) , though in terms of absolute height , this still did not give the Strv 103 any significant advantage . Its most likely opponent after all , the T - 72 , is only 2 . 23 meters in height with its turret versus the 2 . 14 meters of the Strv 103 ( a mere 3 . 5 inches shorter ) . However , tanks occasionally deploy themselves into hull - down firing positions , either purpose dug or using the crest of a hill , in order to reduce the exposure of the vehicle to enemy fire . In this firing position the level of exposure is determined by the distance between the bottom of the gun barrel to the top of the turret or vehicle , and the angle to which the vehicle is able to depress the gun barrel . Because the Strv 103 orients the entire tank to depress and elevate the barrel , in a hull down position it has a very low apparent height and subsequent visual profile to the enemy . It can also lower the hull 13 centimeters . Such static use of a tank is at odds with the very concept of a tank , i . e . , a mobile , protected gun platform able to bring heavy firepower to bear upon the enemy while attacking . Hence the S - Tank must be considered a strictly defensive vehicle . This is not the first time such a system had been used : it was common among World War II - era tank destroyer s and assault gun s , but in a tank , the ability to quickly aim a turret provided always proved to be great asset . However , some tank destroyers , such as the " Jagdpanther " , were both relatively cheap to make and very effective in defensive positions . Berge ' s design tried to solve the aiming problem through the use of a fully automated transmission and suspension system , which would turn and tilt the tank under gunner control . The gun itself would be fixed to the hull . Unfortunately , this made it impossible to use a stabilized gun . As a result , the tank could not accurately move and fire at the same time . However , during the period the S - tank was in service , turreted tanks rarely fired on the move , and especially not when used defensively . Other features of the tank were also quite radical . The gun , a Bofors 105mm L / 62 ( and able to use the same ammunition as the British 105mm L7 ) would be equipped with an autoloader , allowing the crew to be reduced to two ; most designs of the era used a crew of four , while the S - Tank would eliminate the loader and gunner . Room was available for an extra crew member , the rear driver , who faced the rear of the tank 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 . The commander and gunner / driver both had the same set of sights and controls to fire the gun and drive the tank . Additionally the tank was powered by two engines , a 240 hp Rolls - Royce K60 diesel for cruising and turning the tank for aim , and a 300 hp Boeing 502 turbine for dashing at high speed . 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 . In 1958 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 of 10 was placed in 1960 . With minor changes , the S - Tank was adopted as the Stridsvagn 103 ( " 103 " from the fact that it was the third tank accepted with a 10 cm gun ) and full production started in 1967 and ended in 1971 with 290 delivered . The changes included a new gyrostabilised commander ' s cupola armed with a 7 . 62 mm KSP 58 , and upgraded frontal armour . A screen , similar to those of the " Panzer " IV " Ausf . " J of World War Two , was available to help defeat HEAT rounds ; however , it was kept secret for many years and was only to be fitted in the event of war . The Strv 103 was 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 6 km / h in water . One tank in each platoon was fitted with a blade under the front hull that allowed it to dig itself into the ground for added protection . The Stridsvagn 103 never saw combat and so its design remains unproven , unlike turreted main battle tank s . 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 . 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 BAOR 1973 , the 103 was tested against the Chieftain . 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 the 103 fired more accurately than the M60A1E3 , but on an average 0 . 5 seconds slower . Strv 103B . As the weight of the Strv 103 had increased compared to the pre - production tanks the 103 turned out to be underpowered . 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 was soon upgraded to B - standard . Strv 103C . An upgrade program was started in 1986 to fit all vehicles with improved fire control systems . Also , each S - Tank 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 290 hp ( 216 kW ) Detroit Diesel with additional fuel tanks , and added a new laser rangefinder . There was some consideration of adding both reactive and / or appliqué armour in the early 1990s , but in the end the S - Tank was instead phased out of Swedish service in favour of the Leopard 2 , which entered service in 1997 . The last year in which the S - Tank were used to train tank crews was 1997 . Strv 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 . This prototype was used during the trials for the new main battle tank system for the Swedish armed forces alongside all the other tanks tested . For a few years this prototype was even tested under remote control . The only Strv 103D ever built is today on display at the Axvall armor museum , together with some 103C models . They are all still in running order .