The League failed in its supreme test. It failed to contain the aggressive action of the Axis powers—Japan, Germany, and Italy—and thus failed to halt the drift toward a new world war. Beginning in 1931, Japan, a permanent member of the League's Council, waged a war of aggression against China, in defiance of both the Council and the Assembly. Although the League did impose economic sanctions against Italy, another permanent member of the Council, when it wantonly invaded Ethiopia in 1935, support was halfhearted and the action unsuccessful. The League was unable to do anything against the illegal reoccupation of the Rhineland in 1936 by Germany, still another permanent member of the Council; nor could it offer more than verbal protests against German and Italian intervention in the Spanish Civil War or the forcible incorporation of Austria into Germany in March 1938 and of Czechoslovakia into Germany the following year. The cumulative effect of these failures strengthened Hitler's belief in the impotence not only of the League itself but also of its principal remaining members. During the summer of 1939, when the world moved ever closer toward war, and even when Hitler's armies marched into Poland on 1 September 1939, not a single member called for a meeting of the League's Council or Assembly.
The League's balance sheet in political matters was not wholly negative, however. It was able, for example, to settle the dispute between Finland and Sweden over the Aland Islands, strategically located in the Gulf of Bothnia; the frontier controversy between Albania, Greece, and Yugoslavia; the potentially explosive border situation between Greece and Bulgaria; and the dangerous conflicts between Poland and Germany over Upper Silesia and between Germany, Poland, and Lithuania over Memel. Through the League's Permanent Court of International Justice, a border controversy between Czechoslovakia and Poland was settled, as were the disputes between Great Britain and Turkey over the Mosul area and between France and Great Britain over the nationality of Maltese residents in the French protectorates of Morocco and Tunisia. The League also stopped the incipient war between Peru and Colombia over territorial claims in the upper Amazon basin.
In addition to these successful peacekeeping activities, the League financially assisted the reconstruction of certain states, notably Austria, and was responsible for administering the Free City of Danzig and the Saar Territory. (The latter was transferred to Germany following a plebiscite in 1935.) It also carried out important humanitarian work. Some of its nonpolitical activities continued throughout World War II, and its secretariat did valuable preparatory work for the emerging UN. The League of Nations was not officially dissolved until April 1946, five months after the new world body came into being.