In which year was the League of Nations established?

The League of Nations was officially established on January 10, 1920. This foundational date marked the culmination of efforts after World War I to create an international organization aimed at maintaining peace and preventing future conflicts. The Treaty of Versailles, which formally ended the war, incorporated the Covenant of the League of Nations, setting out its principles and structure.

While 1918 and 1919 are close to the time when discussions and planning for the League were ongoing following the war, it was not until January 2020 that the organization was legally recognized and began its operations. The year 1921 comes after the establishment and does not pertain to the founding. Therefore, the year 1920 is definitively the correct answer as it marks the true beginning of the League's activities.