After Germany surrendered in November 1918, Höss finished high school. Soon, he joined the nationalist paramilitary groups that were forming. First, he joined the East Prussian Volunteer Corps. Then he joined the " in the countries around the Baltic Sea, Silesia, and the Ruhr. Höss participated in the armed terror attacks on Polish people during the Silesian Uprisings (when the Polish people tried to break away from German control). He also participated in terror attacks on French nationals during the Occupation of the Ruhr (when the Ruhr valley in Germany was occupied by France and Belgium).