The causes of the 1914-1918 First World War can be categorised into militaristic factors, alliances, imperialism and nationalism. The competition between nations to develop superior militaries between Britain and Germany increased as Germany began to develop the same Dreadnoughts that Britain had pioneered. These tensions contributed to the pre-war feeling and the initiation of the First World War as the tensions were finally sparked in the June 28 1914 assassination of Archduke Franz Ferdinand. Additionally, the combination of Russia's 1914 mobilisation of troops, which was seen as an aggressive act of war, and Germany's fear that if they did not act soon then they would lose the advantage of having the largest military in the world and would be less likely to achieve an outcome favourable to Germany contributed to the initiation of the war and particularly the initiaiton of the war at this point in history.
Alliances also contributed to the commencement of war in 1914 as Kaiser Wilhelm felt encircled by the Triple Entente (Britain, France and Russia) and therefore contributed to tensions between Germany and these nations. The alliance system also turned the Balkan War into a world war as the alliances obligated other nations to join the war effort.
Both nationalism and imperialism, which in themselves are intrinsically linked, contributed to the initiation of the First World War. Imperialism is the policy of expanding territory and influence, while nationalism is the belief that ones own nation is superior to anothers. Without the belief that your nation is superior to another one, there would be no desire to spread influence. Tensions as a resut of imperialism can be found in the Moroccan Crises of 1906 and 1911 when Kaiser Wilhelm attempted to spread influence into Morocco while France was trying to do the same, resulting in tensions between the two nations. Nationalism was a further factor that contributed not only to imperialism tensions but to it's own form of tension particularly in the Balkan Crises. Serbian nationalism made the Serbians under Turkish and Austro-Hungarian rule more determined to be free to rule themselves. This led to rebellions and terrorism which destabilised the Balkans and led to the Balkan war, which then became the First World War through the alliance system.