High Quality Content by WIKIPEDIA articles! Raupenschlepper Ost, literally "Caterpillar Tractor East", is more commonly abbreviated to RSO. This fully tracked, lightweight vehicle was conceived in response to the poor performance of wheeled and half-tracked vehicles in the mud and snow during the Wehrmacht`s first winter on the Soviet Front. The RSO may have been inspired by very similar full-tracked small tractors in use in other armies, mostly originated from the pre-war light to medium series of Vickers artillery tractors.