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.