Acronym MAIN
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* **M**ilitarism: Large armies, arms race
* **A**lliances:
* Triple Entente (France, UK, and Russia) with the addition of the United States, Italy, and Japan
* Triple Alliance (Germany, Austro-Hungarian Empire, and Italy) with the addition of the Ottoman Empire and Bulgaria. However, Italy soon switches sides.
* **I**mperialism: It drove competition between European Powers. In addition, it bought the whole world into the war
* Nationalism: Nationalism started the war where Serbian nationalists who were under the rule of the Austro-Hungarian empire wanted their freedom. In addition, nationalism within Europena powers further drove competition.