The M.A.I.N. Causes of The Great War M: MilitarismA: Alliances (tangled)I: ImperialismN: Nationalism
Germany performed this before the war started, in a time of peace. This concerned the other European powers and made them pay much more attention to Germany.
Militarism
Germany: This should protect me from France, they could declare war on me.
Alliances (Tangled Alliances)
The alliances created during this war usually got into conflict, and this was a major start to the war. During a time of peace, the Chancellor of Prussia, who feared France, started a treaty with Austria-Hungary, this starts many conflicts in the future.
Imperialsm
With the Age of Imperialism done, the European powers had grown to feel mistrust and rivalry between each other. This grew from the competition to achieve as much land as they could.
That land belongs to Russia!
Nationalism
While nationalism grew in Europe, people of these nations began to feel more devoted and entitled to their country. They felt like their countries deserved more land, resources, and markets than the others.
No, these lands and resources are Germany's!
That stuff actually belongs to Britain.
Then, the last straw to be pulled. The assassination of Archduke Franz Ferdinand led to the domino effect of blame and declaration of war that caused this massive conflict between nations.