The M107 175 mm self-propelled gun was used by the U.S. Army and U.S. Marine Corps from the early 1960s through to the late 1970s. It was part of a family of self-propelled artillery that also included the M110. It was intended to provide long-range fire support in an air-transportable system. It was exported to several other countries including Germany, South Korea, Spain, Greece, Iran, Israel, Italy, the Netherlands, the United Kingdom, and Turkey. The M107's combat history in U.S. service was limited to the Vietnam War; it also saw extensive combat use in Israeli service. The M107 shared many components with, and in many cases was replaced by, later versions of the M110 203 mm howitzer. Although withdrawn from U.S. service in the late 1970s, it continues in service with some armies as of 2019. Design and production history During the 1950s, the standard U.S. Army motorized 203mm artillery piece was the M55, based on the chassis and the turret of the M53 155mm self-propelled gun, which used some components from the M48 tank. The weight of the M55, at 44 metric tons, prohibited air transportation and its gasoline engines limited its range to approximately 260 km, as well as presenting an explosion hazard in combat. This led the U.S. Army to issue a requirement for a new series of self-propelled artillery systems: the new weapons were to be lighter, so as to be transportable by air, and would continue the practice of deriving several vehicles from the same chassis, to simplify maintenance and training. The Pacific Car and Foundry (Paccar) company developed several prototypes. The 175 mm T235 self-propelled gun and 203 mm T236 self-propelled howitzer were driven by a diesel engine and, aside from the different armament, were essentially the same vehicle. They were introduced into U.S. Army service as the M107 and M110 in 1962 and 1963, respectively. Paccar received the M107 and M110 design contracts and initial manufacturing bid from Detroit Arsenal. This was based on patented key features of the M55: the gas equilibrator, which improved barrel balance, enabling the gun to be elevated more easily (this was linked to a hydraulically controlled pendulum); an improved ratchet mechanism to improve aiming; a new design of hydraulic recoil mechanism; and hydraulically controlled chassis suspension bracing when the gun was firing. Two other firms also produced the M107: FMC, between 1965 and 1980, and Bowen-McLaughlin-York. Both