The event that started the First War was the assassination of Archduke Francisco Ferdinando, on June 28, 1914, in the Bosnian capital, Sarajevo. Francisco Ferdinando was heir to the throne of the Austro-Hungarian Empire and was assassinated by the militant of the Serbian secret organization Black Hand, Gavrilo Princip. Francisco Ferdinando wanted to elevate Bosnia and Herzegovina to the level of importance of Austria, forming a triple monarchy, composed of Austrians, Hungarians and Slavs. Serbian nationalist groups, such as the Black Hand, did not want this alliance to occur, guiding Gavrilo Princip to carry out the attack.
It was precisely this infinity of national conflicts that gave rise to the first major world-wide conflict. But the focus of the fighting occurred even on the European continent. On August 1, 1914, the Austro-Hungarian Empire declared war on Serbia, due to the attack on the heir to his throne. Russia immediately sided with Serbia, activating a system of alliances that had been developing since 1870.
On the one hand, the Triple Alliance had been formed, composed of the German Empire, the Austro-Hungarian Empire and Italy. On the other hand, the Triple Entente, formed by France, England and Russia, had already been formed.
With Russia's support for Serbia, Germany sided with the Austro-Hungarian Empire against Russia, forcing France and England into the conflict. Italy declared itself neutral at the start of the war over rivalry with Austro-Hungarians over territories on the border between the two countries. In addition, the war was understood for North Africa and the Middle East, a stage of dispute between the countries for the colonies.