The League of Nations is generally considered to be a failure in the eyes of historians. This is mostly due to the fact that World War II started on its watch. The perceived failure of the League of Nations has two major causes. First, the United States, which had emerged after World War I as an important geopolitical player, refused to enter the League. Secondly, the League did not have an enforcement mechanism, particularly a military apparatus. There are a number of arguments to suggest the League of Nations was a failure. The League failed to stop a number of wars from occurring, which was a primary goal of its establishment. Examples include Greece and Turkey, and Poland and Russia. The League of Nations also failed to stop the aggression of Japan and Nazi Germany which hastened the return of large-scale war in Europe.
Despite these failures, it can also be argued that the League of Nations had its share of successes. The League helped Austria and Hungary with its fiscal crisis by securing loans to stabilize its currency. Also, the League of Nations did, in fact, prevent major conflicts between some of the European powers. This was true in mediating a resolution between Yugoslavia and Albania in 1920 and Greece and Bulgaria in 1925.