There were many causes of the Second World War such as Treaty of Versailles, failure of the League of Nation and Nazi-Soviet Pact. All those causes played important roles in causing the World War Two.
The terms of the Treaty of Versailles were too harsh. It asked too much reparation, reduction in army and territory. This certainly made Germany upset and it made them want to take revenge, even Lloyd George admitted that it was too harsh and cause another war later. When Hitler came to power, he promised to break the terms one by one, which was to be a step to the war. The League of Nation was established to keep peace and make Germany follow all the terms. However, the League of Nation has failed its aims; it couldn’t even control its own key members. USA’s policy of isolationism made the League even worse, USA was one of the strongest in the world but it didn’t do anything for Europe’s peace. The League needed some financial and military support from the USA but they couldn’t get any so this made the League weaker. Japanese expanded in Asia, invaded Manchuria and Italy invaded Abyssinia. They were one of the Council members but left the League when they were asked to keep the peace. They completely ignored the League because they knew that the League is toothless without any army. They also became Hitler’s World War 2 allies and this made Hitler confident to start the war as he has some militarised and powerful allies.
The rise of the dictators in Europe was also a good factor. Dictators like Hitler and Mussolini came to power and made their countries militarised. The Hossbach Memorandum, which was Hitler’s expansion plan of German Empire caused Germany to start getting back some territories and invade other nations. The Great Depression made countries to get some colonies, it made strong countries to sell their