A power-operated system for actuating the rear doors or liftgates of motor vehicles includes a strut assembly having two struts, each strut mounted on one side of the door between the door and the vehicle's door frame. One end of each strut is connected to a powered rotating arm. To open the door, the rotating arms change the angular orientation of the struts such that they have a substantial mechanical advantage. In this position, the force provided by the struts overcomes the weight bias of the door, thus opening the door. To close the door, the rotating arms change the angular orientation of the struts such that the struts have a decreased mechanical advantage, reducing the force provided by the struts, and therefore causing the door to fall closed under its own weight bias. A control system for controlling the power-operated system is also disclosed.