The League of Nations, formed in the aftermath of World War I with the hope of preventing another war, failed because it was unable to prevent conflict and resolve international disputes.
The League was based on the principle of collective security, meaning that all member states would come to the aid of any member state that was attacked. However, this system was flawed because it required unanimous consent from all members for action to be taken against an aggressor. This meant that a single state could veto intervention measures against an aggressor and therefore prevent collective action against it.
In addition, many of its members were drawn into World War II due to aggressive expansionism by Japan and Germany during the 1930s. These countries engaged in military expansionism in order to expand their territories or spheres of influence at the expense of other countries such as China and Russia. This gave rise to tensions between them and their neighbors as well as between them and other members of the League who felt threatened by these actions (such as Britain).
The League also failed because it could not effectively respond to aggression from its member states, leading to tensions between them which eventually erupted into full-scale war (World War II). Furthermore, when Germany invaded Poland on September 1st 1939 two days after signing a non-aggression pact.
