In September 1945, the Soviets appointed Rau a member of the provisional chairmanship of the Province of Brandenburg with the title of a vice-president and responsibility for food, agriculture and forests. Rau succeeded Edwin Hoernle, who had held this position since the end of June and became chairman of the central administration for agriculture and forests in the Soviet Occupation Zone (SBZ). In his new position, Rau was a member of the commission for the execution of the land reform in the province. In spring 1946 he assumed responsibility for