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.
This led the U.S. Army to issue a requirement for a new series of self-propelled artillery: lighter, so as to be transportable by air, while continuing the practice of deriving several vehicles from the same chassis, which simplified maintenance and training.