How Strong Was the League of Nations?

The League of Nations was created from the Treaty of Versailles after WWI. However, unfortunately no countries were willing to create the League of Nations. They joined and created the League because Wilson, the president of one the strongest countries U.S, said he wanted to create a better world. So, the countries in the League seemed lacking of eagerness. How effective was the League of Nations, then?
It was true that the League of Nations had contributed to world peace, in spite of the lack of eagerness. For example, they successfully stopped the conflict between Yugoslavia and Albania, and between Finland and Sweden. In addition, they arbitrated between Germany and Poland, Britain and Turkey, and Greece and Bulgaria. Without the League of Nations there were many wars between countries. So, the League of Nations contributed to the peace a lot.
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