America's Foreign Policy Practice Exam 2025 - Free Practice Questions and Study Guide

The key lesson learned regarding membership from the League of Nations when establishing the United Nations is that the absence of significant powers can critically undermine the effectiveness of the organization. The League of Nations, which was created after World War I to promote peace and cooperation among countries, faced significant challenges, particularly due to the nonmembership of the United States. The U.S. was one of the world's leading powers, and its lack of participation diminished the League's authority and capacity to enforce its decisions.

Recognizing this, the founders of the United Nations sought to include all major powers in the new organization to ensure a more robust and effective response to global conflicts and issues. This approach aimed to foster cooperation and prevent the failures that contributed to the disbandment of the League. The importance of the inclusion of key nations is emphasized by the structure and membership principles established in the UN Charter, which also highlights the importance of having the participation of both major powers and smaller states to create a more balanced and effective international organization.