The S- Tank was a Swedish main battle tank. It was known for its unconventional turretless design. It was formed Swedish armored forces during the 1970s, 80s and part of the 90s, and total of 300 were made. An upgrade Strv 103C was started in 1986 to fit all vehicles with improved fire control systems and replaced the Rolls-Royce engine with a newer 290 hp Detroit Diesel with additional fuel tanks, and added a new laser rangefinder, and added both reactive armor and additional armorplates in the early 1990s, but in the end the S-Tank was instead phased out of Swedish service in favour of the Leopard 2 in 1997.