Answer:
The idea of collective security failed to keep the peace between 1920 and 1935 due to the fact that the league was unable to act against the larger powers due to its lack of support, and the depression.
Explanation:
They cited the failure of the United States of America to join the League from the start and the rise of the Soviet Union outside the League as one of the major reasons why the League failed as instrument for the development and enforcement of collective security.
