The Treaty of Versailles (1919) stipulated the temporary occupation of the Rhineland by Allied troops and its eventual demilitarization. The occupation was intended to secure Germany's reparations payments while creating a buffer zone to protect France and Belgium from German attacks. As shown on this map, there were three occupation zones: A zone around Cologne and around the Aachen area (Belgian and British), a zone that included Koblenz (American, French), and a large zone that included Mainz and Trier (French). The Inter-Allied Rhineland Commission, based in Koblenz, was responsible for administering the Allied occupation. The occupation period formally began after the Treaty of Versailles came into force in 1920 and was gradually phased out, ending with the evacuation of the Mainz zone in June 1930. The map also shows the areas around Duisburg and Essen, which were occupied by French and Belgian troops from 1923 to 1925 (Ruhr occupation) in order to demand reparations payments after the First World War and to control coal and steel production. French troops also occupied parts of Hesse, including Frankfurt and some surrounding areas, from 1920 until the formal end of the occupation in 1929/30. As stipulated by the Treaty of Versailles, the Saarland was under the mandate of the League of Nations from 1920 until the plebiscite of 1935.