Raupenschlepper Ost
Raupenschlepper Ost (German: "Caterpillar Tractor East", more commonly abbreviated to RSO) was a fully tracked, lightweight vehicle used by the Wehrmacht in World War II. It was conceived in response to the poor performance of wheeled and half-tracked vehicles in the mud and snow during the Wehrmacht's first autumn and winter on the Soviet Front. The RSO was a contemporary with somewhat similar Allied full-tracked small artillery tractors in use in other armies (such as the Soviet STZ-5 "Stalingradets", and the U.S. Army's M4 tractor), mostly originated from the pre-war light to medium series of Vickers artillery tractors.