Final answer:
The League of Nations was established to maintain peace but lacked effectiveness due to the absence of the United States and no military enforcement power.
Step-by-step explanation:
The League of Nations was conceived as an international organization to promote peace and prevent future wars, but its practical efficacy was limited. The most telling evidence that the League struggled in practice is found in the fact that the United States never joined, which critically weakened its global influence and capabilities. Without the participation of one of the world's most powerful nations, the League had less authority in enforcing collective security measures. Additionally, the League had no military power to enforce its resolutions, limiting its means to respond to acts of aggression. The 1930s highlighted these weaknesses as the League proved unable to effectively address invasions or conflicts, such as Japan's invasion of Manchuria and Italy's invasion of Ethiopia, largely due to its lack of real power and the absence of support from essential member nations.
Despite President Woodrow Wilson's vision and the theoretical soundness of the idea, the inability to take decisive action or to include all major powers such as the US, showcased the League's struggle to implement its ideals. The League eventually ceased to exist with the onset of World War II, demonstrating the gap between its lofty goals and the harsh realities of international politics.