Many nations, on the eve of the First World War, also known as the "Great War", have become aware of the emancipation of a national being. Immediately before the Great War, liberation wars for the liberation of the Balkan peoples from the Turks were led. The Great Turkish Empire was already reduced in 1913 to more or less the area of today's Turkey. National consciousness grew among the people who were within the Austro-Hungarian monarchy, mainly the Slovenian peoples. On the other hand, Germany's expansionist tendencies have grown, fueled by nationalism, as are tensions between the great powers. All this, of course, when it comes to great powers, have interest and profit for the background. It emphasizes nationalism at the forefront as a tool for achieving goals. This leads to the arming of these great powers and the improvement of the technology of warfare.
When all this is done, the great powers strive to expand, arm themselves, expand their own war arsenal, and the smaller ethnic group strives for the liberation of those parts still under Austro-Hungarian rule. These are the Serbs' aspirations for the parts of Bosnia where the Serbs live to be free as the already free parts of the Balkans with the Serbian population, after the expulsion of the Turks. There is the aspiration of other nations in Austria-Hungary to free themselves.
The Austro-Hungarian interest was to build the Vienna-Istanbul railroad and here they saw Serbia as an obstacle. In this general conflict, the assassination of Archduke Franz Ferdinand in Sarajevo in June 1914 was carried out. This was a direct cause for war, and the background was all previously mentioned that nationalism:
Created tension between Europian powers,
Countries developed new technology and war weapons,
Ethnic groups were seeking self-determination