Explain why world war on broke out in 1914

World war 1 broke out in 1914 because a group of Serbian nationalists (The Black Hand) assassinated the duke of Austria-Hungary. Austria -Hungary threatened Serbia with a bunch of wishes that they wanted Serbia to due for them. Due to the treaty between Serbia and Russia, Serbia said no. Germany, who had a treaty with Austria-Hungary threatened to attack if Russia mobilized its army. Russia did and Germany invaded Belgium. This brought Great Britain and France into the war.

Hey mate here is the answerthe correct answer is ( gold) may it will you