Why did world war 1 break out in Europe

The cause of World War I was the assassination of Archduke Franz Ferdinand of Austria-Hungary In June 1914. he was assassinated by a Serbian nationalist named Gavrilo Princip who shot the Archduke and his wife while they were driving through Sarajevo, Bosnia which was part of Austria-Hungary and died of their wounds.

The assassination of Archduke Franz Ferdinand in Sarajevo on 28th June 1914, it triggered a chain of events that resulted in World War 1.