Answer:
Cause : The first world war was a direct result of these four main causes, but it was triggered by the assassination of the Austrian archduke Franz Ferdinand and his wife. The four main causes of World War 1 are nationalism, imperialism, militarism, and alliances.
How it started :The spark that set off World War I came on June 28, 1914, when a young Serbian patriot shot and killed Archduke Franz Ferdinand, the heir to the Austro-Hungarian Empire (Austria), in the city of Sarajevo. The assassin was a supporter of the Kingdom of Serbia, and within a month the Austrian army invaded Serbia.
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