Though the Citizens' Defense was involved in internal struggle, it soon became entangled in foreign conflict. Indeed, many of its leaders saw its primary purpose as providing defense for Germany's frontiers. In March of 1921, the Allies, citing the Treaty of Versailles, demanded the dissolution of the illegal paramilitary and occupied two German cities along the Rhine. But Germany did not disband it. That same month, German Communists attempted a short-lived revolt. And in May, Germany sent the Citizens' Defense to help crush a Polish uprising in the important coal province of Upper Silesia. (The fighting had been brought about by the controversy over the results of the plebiscite that had been held there to determine whether Upper Silesia would be controlled by Germany or Poland.)