Question

The Blank was an international organization designed to prevent war that was set up after World War 1.

Answer 1

Answer:

League of Nations

Explanation:

The League of Nations were developed after WWI, United Nations after WWII

Answer 2

Answer is: League of Nations.
League of Nations was formed at the end of WWI (10 January 1920) a result of the Paris Peace Conference. League of Nations was first international institution whose mission was to maintain world peace. At 1935 it has 58 members (states). The League of Nations endured for 26 years.