In 1914 World War One broke out in Europe. It was the single largest struggle the world had ever seen, between Europe's great powers and their allies. Prior to the outbreak of war in 1914 Europe was controlled by the five great powers Austria-Hungary, France, Germany, Great Britain and Russia. There are a number of causes for the Great War, these being the over developed alliance system between the powers, Imperialism, the growth of Militarism and Nationalism. No one single factor is responsible for the Great War but a combination of them all.
Imperialism and Militarism was a source of conflict among the great powers of Europe. Britain at the time was the largest empire in the world. Germany was a relative newcomer to Imperialism and sought to secure her place in the sun, just like Britain and France had done with their extensive Asian and African colonies. Kaiser Wilhelm II was eager to establish Germany as a Colonial and European power, with the help of Admiral Tirpitz started the construction of a naval fleet. This worried Britain who was the largest naval power in the world and felt a German navy would rival her colonial interests as well as becoming a danger in the North Sea. This started a naval race and created tension and competition between the two countries. With the increase of Europe's armies by the beginning of 1914 the continent was in a state of armed peace.
Nationalism was a major source of provocation during the late 19th and early 20th century. The ethic of putting your nation before all others created the idea of competing nation-states each vying to become richer and more powerful than the others. This led to the rush in Germany to build a Colonial Empire and the arms race between the continental powers. From Nationalism arose the idea of defined borders, but this was not the case for the Slavs. They shared a common cultural heritage and language but were scattered amongst more than one nation, wishing to have their own country.