What was the international organization established by the Treaty of Versailles after World War I?

The League of Nations was the international organization established by the Treaty of Versailles after World War I. Formed in 1920, its primary purpose was to promote peace and cooperation among countries, preventing the kind of destructive conflict that had occurred during the war. The League aimed to facilitate diplomacy, promote disarmament, and address issues of international concern through collective security and negotiation.

Its establishment marked a significant moment in international relations, as it was the first organization aimed at fostering global collaboration and preventing future conflicts on such a scale. Although it ultimately struggled with effectiveness and was unable to prevent the outbreak of World War II, the League of Nations laid the groundwork for future international organizations, most notably the United Nations.

The other organizations listed have different contexts and timelines: the United Nations was established after World War II with a broader mandate, the World Trade Organization focuses on global trade agreements and policies, and NATO is a military alliance formed during the Cold War. Thus, the League of Nations stands out as the correct answer in the context of the Treaty of Versailles.