The main causes of the first world war were:
Militarism
There was a growth of millenarianism in nations. many nations had sophisticate weapons and well trained military.
Alliances
The alliances that were formed between nations was part of the war. There were the axis and the allied powers.
Nationalism
The increase in nationalism and the need to protect country and property was a part of the war.
Imperialism
Some nations has powers over other countries. They controlled the affairs and the resources in these areas.
Death
The killing of Franz Ferdinand was partly the reason why the war started.
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