Why did World War I break out in 1914?

In this essay I'm going to be explaining the causes of WWI. There are four main causes of WWI. They are Nationalism, Imperialism, Militarism and Alliances. The assassination of Archduke Ferdinand was only the "spark" which set off the "barrel of gunpowder". The four causes had created so much tension in Europe that it only needed one event to trigger the war. I will break down the four causes into long term, medium term and …

…Events". Austria assumed that Serbia was involved in the assassination. Austria wanted Serbia to agree to 10 requests; otherwise they would declare war. Serbia agreed to every request except the last one. That started the fighting. So, the start of the war was just like a barrel of gunpowder. Gradually the barrel was built and filled with explosive. One small event was "like lighting the fuse" It led to a big explosion called World War One.