The League of Nations was officially dissolved on April 18, 1946, after failing to prevent World War II. Its functions and responsibilities were transferred to the newly established United Nations, which aimed to learn from the League's shortcomings.

Spain withdrew from the League of Nations on April 19, 1939, following the Spanish Civil War and the establishment of Francisco Franco's regime. This withdrawal further weakened the League, as it struggled to maintain its influence amid growing global tensions.

On October 3, 1935, Italy invaded Ethiopia, defying the League of Nations' principles. The League's failure to effectively respond to this aggression demonstrated its inability to maintain peace and deter militaristic actions by member states.

Japan announced its withdrawal from the League of Nations on February 24, 1933, following the League's condemnation of its invasion of Manchuria. This marked a significant challenge to the League's authority and highlighted its limitations in enforcing decisions.

On September 8, 1926, Germany was admitted to the League of Nations, marking a significant step in its post-World War I rehabilitation. This inclusion was part of the broader Locarno Treaties, aimed at stabilizing Europe and fostering reconciliation.

The first Assembly of the League of Nations convened on November 15, 1920, in Geneva. Representatives from 41 member countries gathered to discuss international issues and set the agenda for the League's future activities.

The League of Nations was officially founded on January 10, 1920, with the entry into force of the Treaty of Versailles. It aimed to promote peace and cooperation among countries, with its headquarters established in Geneva, Switzerland.

The Treaty of Versailles was signed on June 28, 1919, officially ending World War I. The treaty included the Covenant of the League of Nations, establishing the League as an international organization to maintain peace and resolve international disputes.

The proposal for the League of Nations was made during the Paris Peace Conference on January 25, 1919. The idea was championed by U.S. President Woodrow Wilson as part of his Fourteen Points, aiming to prevent future conflicts through collective security and diplomacy.