(a) Failure of the League of Nations: 

1. All the great powers were not its members. The United States was not a member at all. In 1925, Germany joined the organization while Russia was allowed entry in 1934. Later, both Germany and Japan left the League. The League, therefore, lacked universal representation. 

2. The permanent members always opposed decisions which went against their own interests. 

(b) Aggressive Nationalism of Germany:Germany’s desire to become a world power and the adoption of policy of militarisation greatly contributed to the Second World War. Hitler, after gaining power, embarked on the path of expansion of German Empire. He annexed Austria, occupied Rhineland and proceeded to occupy Czechoslovakia. Thereafter, he set his eyes on Danzia and Poland. It was the aggressive nationalism of Hitler which led to the Second World War. 

(c) Policy of Appeasement: Appeasement meant a policy of conciliating an aggressive power at the expense of some other country. The Western Powers followed the policy of appeasement because they felt that the dictators had a real cause of grievance and if their grievances were removed they would leave others alone. The Western Powers wanted to check the rising tide of Communism and Russian Bolshevism. They, therefore allowed Germany to re-arm and to remilitarise the Rhineland and capture Austria and Czechoslovakia. But for the Western countries policy of appeasement, Fascism or Nazism could not have survived so long and would not have been able to unleash the Second World War. The League of Nations watched helplessly when Italy attacked and annexed Abyssinia.