Chamberlain's policy of appeasement emerged from the failure of the League of Nations and the failure of collective security. The League of Nations was set up in the aftermath of World War I in the hope that international cooperation and collective resistance to aggression might prevent another war. Members of the League were entitled to the assistance of other members if they came under attack. The policy of collective security ran in parallel with measures to achieve international disarmament and where possible was to be based on economic sanctions against an aggressor. It appeared to be ineffectual when confronted by the aggression of dictators, notably Germany's Remilitarization of the Rhineland, and Italian leader Benito Mussolini's invasion of Abyssinia.