Although the coming of the First World War has aroused much interest and controversy, the question of immediate causes can be answered with considerable certainty.
Darwinism, a theory developed into practice in politics in the form of aggressive colonial conquests has greatly worsened international relations in the early twentieth century. A frantic rush to plant the flag over as many people and as much territory as possible, had serious consequences. Imperialism resulted new tensions among competing European states, and lead to the triumph of nationalism. .
Nationalism was a crucial and underlying precondition of the Great War. It was in the form Serbian aspirations and the pan-German versus pan-Slavic racism of some fanatics. Nationalism also drove a spiraling arms race. Such great powers as Great Britain, France, Russia, Germany, Italy and Austria-Hungary nearly tripled their expenditures on armaments in the period between 1870 and 1914. This led to distrust and hostility between the two most powerful nations: Germany and Great Britain. The leading nations of Europe were soon divided into two aggressive blocks to maintain the balance. .
On June 28, 1914 Archduke Francis Ferdinand and his wife, Sophie, were assassinated by Bosnian revolutionaries during a state visit to the Bosnian capital of Sarajevo. As Austrian-Hungarian government soon found out, that the revolutionary group, dedicated to uniting all Serbians in a single state, was secretly supported by members of the Serbian government. Although the leaders of Austria-Hungary could not know all the details of Serbia's involvement in the assassination plot, they concluded after some hesitation that Serbia had to be severely punished once and for all. In each country people believed that their country had been wronged, and they rallied to defend it. Patriotic nationalism brought unity in the short run. After nearly a month, on July 23 Austria-Hungary presented Serbia with an unconditional ultimatum.