Before, there was the Triple Alliance (Austria-Hungary, Germany, and Italy) and the Triple Entente (France, Great Britain, and Russia). It started when Austria-Hungary assassinated Archduke Francis Ferdinand and Serbia decided that Austria-Hungary was now its enemy. Events took a turn from the worse when allies got in on the action. Since Austria-Hungary and Germany had taken the offensive, Italy broke away. The Triple Alliance became the Central Powers (Austria-Hungary, Germany, and Ottomans). The Triple Entente became the Alliances (Great Britain, France, England, Italy, etc.). Tensions, especially with Germany, rose and wars broke out. At the time, the British had the largest empire in the world and used its colonies to its advantage, consequently making it a world war.
Biggest one is the assassination of Franz Ferdinand.
World War I was caused by a combination of militarism, complex alliances, imperial ambitions, rising nationalism, and the assassination of Archduke Franz Ferdinand. The war escalated rapidly due to these intertwined factors, leading to a domino effect of nations entering the conflict. Ultimately, this transformed a local incident into a global war involving many of the world's powers.
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