What are the main causes of world war 1 ?

1.) nationalism: It is a deep loyalty to one's nation
2.) alliance system: It is the formal agreement of support among countries in the event of an attack
3.)imperialism: The building of power by controlling over colonies. (Countries were arguing over colonies and this caused war).
4.)militarism: It is the preparation of the war.
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When Franz Ferdinand got shot (assassination) 
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