Question

causes of World War 1 and 2

Answer 1

World war 1 reason -- assassination of
Franz Ferdinand who was Austrian archduke and his wife

World war 2 reason --- fascism , japanese expansion , treaty of Versailles , Adolf Hitler with his Nazi party's arising power. ....

Answer 2

The first world war started on 28th July,1914. The main reason for the war to get triggered is the assassination of the crowned prince of Austria-Hungary and the other main reason was the newly raising power of the Germany and Italy trying to compete against the old emerged power Britain for things like raw materials, colonies, places to settle their capitals and earn profit. 

The second world war started on 1st September 1939. The main reason for this war to get triggered is the entry of the Nazi Germany army tanks into Poland for taking over the port of danzig. Little did Hitler the leader of the Nazi Germany party knew that Poland had a pact with the most powerful Britain.
The injustice done to the countries that lost the world war 1 they are Germany, Italy and Japan they had to pay the war money for compulsion and even they had to lose a large part of their territory because the countries that had won the war wanted to re-draw their boundary and according to the Treaty of Versailles they had to give away their colonies away to the countries that won the war. This was the reason for the rise of the Nazism in the countries that lost the war because of hatred.   

There are many long term causes also for the triggering of the both deadliest wars ever were - 
1. Aggressive Nationalism 
2. Imperialism
3. Militarism 
4. Alliance 
5. Craving for power and authority