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.
Give the large amounts of sugar and other goods brought to New England through triangle trade, North America would have benefited most. The Caribbean received manpower in the form of slaves from Africa, while Africa sold its mapower in exchange for goods (lots of rum), meaning it most likely benefited the least.
President Roosevelt decided that Eisenhower not Marshall would be Supreme Allied Commander in Europe.