What was a pivotal failure that led to the dissolution of the League of Nations?

The failure of collective security agreements was indeed a pivotal factor that contributed to the dissolution of the League of Nations. The concept of collective security rested on the idea that member states would come together to defend each other against aggressors, essentially creating a form of mutual defense. However, when crises arose, such as Italy's invasion of Ethiopia or Japan's invasion of Manchuria, the League struggled to mobilize effective responses. Key member states, including the major powers, often acted in their own national interests and did not commit their military resources to enforce League decisions. This lack of action undercut the League’s credibility and effectiveness, leading to disillusionment among member nations regarding its ability to maintain peace and prevent aggression.

In contrast, other aspects like the requirement for unanimous decisions created challenges but were not the primary reason for the League's ultimate inability to function. The excessive power attributed to the US is also misleading, as the US never joined the League, which limited its influence rather than amplifying it. Additionally, overdependence on military intervention was not a characteristic of the League's approach, as it often opted for diplomatic negotiations and sanctions instead, illustrating a fundamental weakness in its framework for enforcing peace.